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2.2.0.M5
Copyright © 2012-2019
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1. Spring Boot Documentation
This section provides a brief overview of Spring Boot reference documentation. It serves as a map for the rest of the document.
1.1. About the Documentation
The Spring Boot reference guide is available as
The latest copy is available at docs.spring.io/spring-boot/docs/current/reference.
Copies of this document may be made for your own use and for distribution to others, provided that you do not charge any fee for such copies and further provided that each copy contains this Copyright Notice, whether distributed in print or electronically.
1.2. Getting Help
If you have trouble with Spring Boot, we would like to help.
-
Try the How-to documents. They provide solutions to the most common questions.
-
Learn the Spring basics. Spring Boot builds on many other Spring projects. Check the spring.io web-site for a wealth of reference documentation. If you are starting out with Spring, try one of the guides.
-
Ask a question. We monitor stackoverflow.com for questions tagged with
spring-boot
. -
Report bugs with Spring Boot at github.com/spring-projects/spring-boot/issues.
All of Spring Boot is open source, including the documentation. If you find problems with the docs or if you want to improve them, please get involved. |
1.3. First Steps
If you are getting started with Spring Boot or 'Spring' in general, start with the following topics:
-
From scratch: Overview | Requirements | Installation
1.4. Working with Spring Boot
Ready to actually start using Spring Boot? We have you covered:
-
Best practices: Code Structure | @Configuration | @EnableAutoConfiguration | Beans and Dependency Injection
-
Packaging your app: Production jars
-
Spring Boot CLI: Using the CLI
1.5. Learning about Spring Boot Features
Need more details about Spring Boot’s core features? The following content is for you:
-
Core Features: SpringApplication | External Configuration | Profiles | Logging
-
Web Applications: MVC | Embedded Containers
-
Testing: Overview | Boot Applications | Utils
-
Extending: Auto-configuration | @Conditions
1.6. Moving to Production
When you are ready to push your Spring Boot application to production, we have some tricks that you might like:
1.7. Advanced Topics
Finally, we have a few topics for more advanced users:
-
Spring Boot Applications Deployment: Cloud Deployment | OS Service
-
Appendix: Application Properties | Auto-configuration classes | Executable Jars
2. Getting Started
If you are getting started with Spring Boot, or “Spring” in general, start by reading this section. It answers the basic “what?”, “how?” and “why?” questions. It includes an introduction to Spring Boot, along with installation instructions. We then walk you through building your first Spring Boot application, discussing some core principles as we go.
2.1. Introducing Spring Boot
Spring Boot makes it easy to create stand-alone, production-grade Spring-based Applications that you can run. We take an opinionated view of the Spring platform and third-party libraries, so that you can get started with minimum fuss. Most Spring Boot applications need very little Spring configuration.
You can use Spring Boot to create Java applications that can be started by using
java -jar
or more traditional war deployments. We also provide a command line tool that
runs “spring scripts”.
Our primary goals are:
-
Provide a radically faster and widely accessible getting-started experience for all Spring development.
-
Be opinionated out of the box but get out of the way quickly as requirements start to diverge from the defaults.
-
Provide a range of non-functional features that are common to large classes of projects (such as embedded servers, security, metrics, health checks, and externalized configuration).
-
Absolutely no code generation and no requirement for XML configuration.
2.2. System Requirements
Spring Boot 2.2.0.M5 requires Java 8 and is compatible up to Java 12 (included). Spring Framework 5.2.0.RC1 or above is also required.
Explicit build support is provided for the following build tools:
Build Tool | Version |
---|---|
Maven |
3.3+ |
Gradle |
5.x (4.10 is also supported but in a deprecated form) |
2.3. Installing Spring Boot
Spring Boot can be used with “classic” Java development tools or installed as a command line tool. Either way, you need Java SDK v1.8 or higher. Before you begin, you should check your current Java installation by using the following command:
$ java -version
If you are new to Java development or if you want to experiment with Spring Boot, you might want to try the Spring Boot CLI (Command Line Interface) first. Otherwise, read on for “classic” installation instructions.
2.3.1. Installation Instructions for the Java Developer
You can use Spring Boot in the same way as any standard Java library. To do so, include
the appropriate spring-boot-*.jar
files on your classpath. Spring Boot does not
require any special tools integration, so you can use any IDE or text editor. Also, there
is nothing special about a Spring Boot application, so you can run and debug a Spring
Boot application as you would any other Java program.
Although you could copy Spring Boot jars, we generally recommend that you use a build tool that supports dependency management (such as Maven or Gradle).
Maven Installation
Spring Boot is compatible with Apache Maven 3.3 or above. If you do not already have Maven installed, you can follow the instructions at maven.apache.org.
On many operating systems, Maven can be installed with a package manager. If you use
OSX Homebrew, try brew install maven . Ubuntu users can run
sudo apt-get install maven . Windows users with Chocolatey can
run choco install maven from an elevated (administrator) prompt.
|
Spring Boot dependencies use the org.springframework.boot
groupId
. Typically, your
Maven POM file inherits from the spring-boot-starter-parent
project and declares
dependencies to one or more “Starters”.
Spring Boot also provides an optional
Maven plugin to create
executable jars.
The following listing shows a typical pom.xml
file:
<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>com.example</groupId>
<artifactId>myproject</artifactId>
<version>0.0.1-SNAPSHOT</version>
<!-- Inherit defaults from Spring Boot -->
<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>2.2.0.M5</version>
</parent>
<!-- Add typical dependencies for a web application -->
<dependencies>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
</dependency>
</dependencies>
<!-- Package as an executable jar -->
<build>
<plugins>
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
</plugin>
</plugins>
</build>
<!-- Add Spring repositories -->
<!-- (you don't need this if you are using a .RELEASE version) -->
<repositories>
<repository>
<id>spring-snapshots</id>
<url>https://repo.spring.io/snapshot</url>
<snapshots><enabled>true</enabled></snapshots>
</repository>
<repository>
<id>spring-milestones</id>
<url>https://repo.spring.io/milestone</url>
</repository>
</repositories>
<pluginRepositories>
<pluginRepository>
<id>spring-snapshots</id>
<url>https://repo.spring.io/snapshot</url>
</pluginRepository>
<pluginRepository>
<id>spring-milestones</id>
<url>https://repo.spring.io/milestone</url>
</pluginRepository>
</pluginRepositories>
</project>
The spring-boot-starter-parent is a great way to use Spring Boot, but it might not
be suitable all of the time. Sometimes you may need to inherit from a different parent
POM, or you might not like our default settings. In those cases, see
Using Spring Boot without the Parent POM for an alternative solution that uses an import
scope.
|
Gradle Installation
Spring Boot is compatible with 5.x. 4.10 is also supported but this support is deprecated and will be removed in a future release. If you do not already have Gradle installed, you can follow the instructions at gradle.org.
Spring Boot dependencies can be declared by using the org.springframework.boot
group
.
Typically, your project declares dependencies to one or more
“Starters”. Spring Boot
provides a useful Gradle
plugin that can be used to simplify dependency declarations and to create executable
jars.
More details on getting started with Spring Boot and Gradle can be found in the Getting Started section of the Gradle plugin’s reference guide.
2.3.2. Installing the Spring Boot CLI
The Spring Boot CLI (Command Line Interface) is a command line tool that you can use to quickly prototype with Spring. It lets you run Groovy scripts, which means that you have a familiar Java-like syntax without so much boilerplate code.
You do not need to use the CLI to work with Spring Boot, but it is definitely the quickest way to get a Spring application off the ground.
Manual Installation
You can download the Spring CLI distribution from the Spring software repository:
Cutting edge snapshot distributions are also available.
Once downloaded, follow the
INSTALL.txt
instructions from the unpacked archive. In summary, there is a spring
script
(spring.bat
for Windows) in a bin/
directory in the .zip
file. Alternatively, you
can use java -jar
with the .jar
file (the script helps you to be sure that the
classpath is set correctly).
Installation with SDKMAN!
SDKMAN! (The Software Development Kit Manager) can be used for managing multiple versions of various binary SDKs, including Groovy and the Spring Boot CLI. Get SDKMAN! from sdkman.io and install Spring Boot by using the following commands:
$ sdk install springboot $ spring --version Spring Boot v2.2.0.M5
If you develop features for the CLI and want easy access to the version you built, use the following commands:
$ sdk install springboot dev /path/to/spring-boot/spring-boot-cli/target/spring-boot-cli-2.2.0.M5-bin/spring-2.2.0.M5/ $ sdk default springboot dev $ spring --version Spring CLI v2.2.0.M5
The preceding instructions install a local instance of spring
called the dev
instance. It points at your target build location, so every time you rebuild Spring Boot,
spring
is up-to-date.
You can see it by running the following command:
$ sdk ls springboot ================================================================================ Available Springboot Versions ================================================================================ > + dev * 2.2.0.M5 ================================================================================ + - local version * - installed > - currently in use ================================================================================
OSX Homebrew Installation
If you are on a Mac and use Homebrew, you can install the Spring Boot CLI by using the following commands:
$ brew tap pivotal/tap $ brew install springboot
Homebrew installs spring
to /usr/local/bin
.
If you do not see the formula, your installation of brew might be out-of-date. In
that case, run brew update and try again.
|
MacPorts Installation
If you are on a Mac and use MacPorts, you can install the Spring Boot CLI by using the following command:
$ sudo port install spring-boot-cli
Command-line Completion
The Spring Boot CLI includes scripts that provide command completion for the
BASH and
zsh shells. You can source
the script (also named
spring
) in any shell or put it in your personal or system-wide bash completion
initialization. On a Debian system, the system-wide scripts are in
/shell-completion/bash
and all scripts in that directory are executed when a new shell
starts. For example, to run the script manually if you have installed by using SDKMAN!,
use the following commands:
$ . ~/.sdkman/candidates/springboot/current/shell-completion/bash/spring $ spring <HIT TAB HERE> grab help jar run test version
If you install the Spring Boot CLI by using Homebrew or MacPorts, the command-line completion scripts are automatically registered with your shell. |
Windows Scoop Installation
If you are on a Windows and use Scoop, you can install the Spring Boot CLI by using the following commands:
> scoop bucket add extras > scoop install springboot
Scoop installs spring
to ~/scoop/apps/springboot/current/bin
.
If you do not see the app manifest, your installation of scoop might be out-of-date.
In that case, run scoop update and try again.
|
Quick-start Spring CLI Example
You can use the following web application to test your installation. To start, create a
file called app.groovy
, as follows:
@RestController
class ThisWillActuallyRun {
@RequestMapping("/")
String home() {
"Hello World!"
}
}
Then run it from a shell, as follows:
$ spring run app.groovy
The first run of your application is slow, as dependencies are downloaded. Subsequent runs are much quicker. |
Open localhost:8080
in your favorite web browser. You should see the following
output:
Hello World!
2.3.3. Upgrading from an Earlier Version of Spring Boot
If you are upgrading from an earlier release of Spring Boot, check the “migration guide” on the project wiki that provides detailed upgrade instructions. Check also the “release notes” for a list of “new and noteworthy” features for each release.
When upgrading to a new feature release, some properties may have been renamed or removed. Spring Boot provides a way to analyze your application’s environment and print diagnostics at startup, but also temporarily migrate properties at runtime for you. To enable that feature, add the following dependency to your project:
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-properties-migrator</artifactId>
<scope>runtime</scope>
</dependency>
Properties that are added late to the environment, such as when using
@PropertySource , will not be taken into account.
|
Once you’re done with the migration, please make sure to remove this module from your project’s dependencies. |
To upgrade an existing CLI installation, use the appropriate package manager command (for
example, brew upgrade
) or, if you manually installed the CLI, follow the
standard instructions, remembering to update
your PATH
environment variable to remove any older references.
2.4. Developing Your First Spring Boot Application
This section describes how to develop a simple “Hello World!” web application that highlights some of Spring Boot’s key features. We use Maven to build this project, since most IDEs support it.
The spring.io web site contains many “Getting Started” guides that use Spring Boot. If you need to solve a specific problem, check there first. You can shortcut the steps below by going to start.spring.io and choosing the "Web" starter from the dependencies searcher. Doing so generates a new project structure so that you can start coding right away. Check the Spring Initializr documentation for more details. |
Before we begin, open a terminal and run the following commands to ensure that you have valid versions of Java and Maven installed:
$ java -version java version "1.8.0_102" Java(TM) SE Runtime Environment (build 1.8.0_102-b14) Java HotSpot(TM) 64-Bit Server VM (build 25.102-b14, mixed mode)
$ mvn -v Apache Maven 3.5.4 (1edded0938998edf8bf061f1ceb3cfdeccf443fe; 2018-06-17T14:33:14-04:00) Maven home: /usr/local/Cellar/maven/3.3.9/libexec Java version: 1.8.0_102, vendor: Oracle Corporation
This sample needs to be created in its own folder. Subsequent instructions assume that you have created a suitable folder and that it is your current directory. |
2.4.1. Creating the POM
We need to start by creating a Maven pom.xml
file. The pom.xml
is the recipe that is
used to build your project. Open your favorite text editor and add the following:
<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>com.example</groupId>
<artifactId>myproject</artifactId>
<version>0.0.1-SNAPSHOT</version>
<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>2.2.0.M5</version>
</parent>
<!-- Additional lines to be added here... -->
<!-- (you don't need this if you are using a .RELEASE version) -->
<repositories>
<repository>
<id>spring-snapshots</id>
<url>https://repo.spring.io/snapshot</url>
<snapshots><enabled>true</enabled></snapshots>
</repository>
<repository>
<id>spring-milestones</id>
<url>https://repo.spring.io/milestone</url>
</repository>
</repositories>
<pluginRepositories>
<pluginRepository>
<id>spring-snapshots</id>
<url>https://repo.spring.io/snapshot</url>
</pluginRepository>
<pluginRepository>
<id>spring-milestones</id>
<url>https://repo.spring.io/milestone</url>
</pluginRepository>
</pluginRepositories>
</project>
The preceding listing should give you a working build. You can test it by running mvn
package
(for now, you can ignore the “jar will be empty - no content was marked for
inclusion!” warning).
At this point, you could import the project into an IDE (most modern Java IDEs include built-in support for Maven). For simplicity, we continue to use a plain text editor for this example. |
2.4.2. Adding Classpath Dependencies
Spring Boot provides a number of “Starters” that let you add jars to your classpath.
Our applications for smoke tests use the spring-boot-starter-parent
in the parent
section of the POM. The spring-boot-starter-parent
is a special starter that provides
useful Maven defaults. It also provides a
dependency-management
section so that you can omit version
tags for “blessed” dependencies.
Other “Starters” provide dependencies that you are likely to need when developing a
specific type of application. Since we are developing a web application, we add a
spring-boot-starter-web
dependency. Before that, we can look at what we currently have
by running the following command:
$ mvn dependency:tree [INFO] com.example:myproject:jar:0.0.1-SNAPSHOT
The mvn dependency:tree
command prints a tree representation of your project
dependencies. You can see that spring-boot-starter-parent
provides no dependencies by
itself. To add the necessary dependencies, edit your pom.xml
and add the
spring-boot-starter-web
dependency immediately below the parent
section:
<dependencies>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
</dependency>
</dependencies>
If you run mvn dependency:tree
again, you see that there are now a number of additional
dependencies, including the Tomcat web server and Spring Boot itself.
2.4.3. Writing the Code
To finish our application, we need to create a single Java file. By default, Maven
compiles sources from src/main/java
, so you need to create that folder structure and
then add a file named src/main/java/Example.java
to contain the following code:
import org.springframework.boot.*;
import org.springframework.boot.autoconfigure.*;
import org.springframework.web.bind.annotation.*;
@RestController
@EnableAutoConfiguration
public class Example {
@RequestMapping("/")
String home() {
return "Hello World!";
}
public static void main(String[] args) {
SpringApplication.run(Example.class, args);
}
}
Although there is not much code here, quite a lot is going on. We step through the important parts in the next few sections.
The @RestController
and @RequestMapping
Annotations
The first annotation on our Example
class is @RestController
. This is known as a
stereotype annotation. It provides hints for people reading the code and for Spring
that the class plays a specific role. In this case, our class is a web @Controller
, so
Spring considers it when handling incoming web requests.
The @RequestMapping
annotation provides “routing” information. It tells Spring that
any HTTP request with the /
path should be mapped to the home
method. The
@RestController
annotation tells Spring to render the resulting string directly back to
the caller.
The @RestController and @RequestMapping annotations are Spring MVC annotations.
(They are not specific to Spring Boot.) See the MVC
section in the Spring Reference Documentation for more details.
|
The @EnableAutoConfiguration Annotation
The second class-level annotation is @EnableAutoConfiguration
. This annotation tells
Spring Boot to “guess” how you want to configure Spring, based on the jar dependencies
that you have added. Since spring-boot-starter-web
added Tomcat and Spring MVC, the
auto-configuration assumes that you are developing a web application and sets up Spring
accordingly.
The “main” Method
The final part of our application is the main
method. This is just a standard method
that follows the Java convention for an application entry point. Our main method
delegates to Spring Boot’s SpringApplication
class by calling run
.
SpringApplication
bootstraps our application, starting Spring, which, in turn, starts
the auto-configured Tomcat web server. We need to pass Example.class
as an argument to
the run
method to tell SpringApplication
which is the primary Spring component. The
args
array is also passed through to expose any command-line arguments.
2.4.4. Running the Example
At this point, your application should work. Since you used the
spring-boot-starter-parent
POM, you have a useful run
goal that you can use to start
the application. Type mvn spring-boot:run
from the root project directory to start the
application. You should see output similar to the following:
$ mvn spring-boot:run . ____ _ __ _ _ /\\ / ___'_ __ _ _(_)_ __ __ _ \ \ \ \ ( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \ \\/ ___)| |_)| | | | | || (_| | ) ) ) ) ' |____| .__|_| |_|_| |_\__, | / / / / =========|_|==============|___/=/_/_/_/ :: Spring Boot :: (v2.2.0.M5) ....... . . . ....... . . . (log output here) ....... . . . ........ Started Example in 2.222 seconds (JVM running for 6.514)
If you open a web browser to localhost:8080
, you should see the following output:
Hello World!
To gracefully exit the application, press ctrl-c
.
2.4.5. Creating an Executable Jar
We finish our example by creating a completely self-contained executable jar file that we could run in production. Executable jars (sometimes called “fat jars”) are archives containing your compiled classes along with all of the jar dependencies that your code needs to run.
To create an executable jar, we need to add the spring-boot-maven-plugin
to our
pom.xml
. To do so, insert the following lines just below the dependencies
section:
<build>
<plugins>
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
</plugin>
</plugins>
</build>
The spring-boot-starter-parent POM includes <executions> configuration to bind
the repackage goal. If you do not use the parent POM, you need to declare this
configuration yourself. See the plugin
documentation for details.
|
Save your pom.xml
and run mvn package
from the command line, as follows:
$ mvn package [INFO] Scanning for projects... [INFO] [INFO] ------------------------------------------------------------------------ [INFO] Building myproject 0.0.1-SNAPSHOT [INFO] ------------------------------------------------------------------------ [INFO] .... .. [INFO] --- maven-jar-plugin:2.4:jar (default-jar) @ myproject --- [INFO] Building jar: /Users/developer/example/spring-boot-example/target/myproject-0.0.1-SNAPSHOT.jar [INFO] [INFO] --- spring-boot-maven-plugin:2.2.0.M5:repackage (default) @ myproject --- [INFO] ------------------------------------------------------------------------ [INFO] BUILD SUCCESS [INFO] ------------------------------------------------------------------------
If you look in the target
directory, you should see myproject-0.0.1-SNAPSHOT.jar
. The
file should be around 10 MB in size. If you want to peek inside, you can use jar tvf
,
as follows:
$ jar tvf target/myproject-0.0.1-SNAPSHOT.jar
You should also see a much smaller file named myproject-0.0.1-SNAPSHOT.jar.original
in
the target
directory. This is the original jar file that Maven created before it was
repackaged by Spring Boot.
To run that application, use the java -jar
command, as follows:
$ java -jar target/myproject-0.0.1-SNAPSHOT.jar . ____ _ __ _ _ /\\ / ___'_ __ _ _(_)_ __ __ _ \ \ \ \ ( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \ \\/ ___)| |_)| | | | | || (_| | ) ) ) ) ' |____| .__|_| |_|_| |_\__, | / / / / =========|_|==============|___/=/_/_/_/ :: Spring Boot :: (v2.2.0.M5) ....... . . . ....... . . . (log output here) ....... . . . ........ Started Example in 2.536 seconds (JVM running for 2.864)
As before, to exit the application, press ctrl-c
.
2.5. What to Read Next
Hopefully, this section provided some of the Spring Boot basics and got you on your way to writing your own applications. If you are a task-oriented type of developer, you might want to jump over to spring.io and check out some of the getting started guides that solve specific “How do I do that with Spring?” problems. We also have Spring Boot-specific “How-to” reference documentation.
Otherwise, the next logical step is to read Using Spring Boot. If you are really impatient, you could also jump ahead and read about Spring Boot features.
3. Using Spring Boot
This section goes into more detail about how you should use Spring Boot. It covers topics such as build systems, auto-configuration, and how to run your applications. We also cover some Spring Boot best practices. Although there is nothing particularly special about Spring Boot (it is just another library that you can consume), there are a few recommendations that, when followed, make your development process a little easier.
If you are starting out with Spring Boot, you should probably read the Getting Started guide before diving into this section.
3.1. Build Systems
It is strongly recommended that you choose a build system that supports dependency management and that can consume artifacts published to the “Maven Central” repository. We would recommend that you choose Maven or Gradle. It is possible to get Spring Boot to work with other build systems (Ant, for example), but they are not particularly well supported.
3.1.1. Dependency Management
Each release of Spring Boot provides a curated list of dependencies that it supports. In practice, you do not need to provide a version for any of these dependencies in your build configuration, as Spring Boot manages that for you. When you upgrade Spring Boot itself, these dependencies are upgraded as well in a consistent way.
You can still specify a version and override Spring Boot’s recommendations if you need to do so. |
The curated list contains all the spring modules that you can use with Spring Boot as
well as a refined list of third party libraries. The list is available as a standard
Bills of Materials (spring-boot-dependencies
)
that can be used with both Maven and
Gradle.
Each release of Spring Boot is associated with a base version of the Spring Framework. We highly recommend that you not specify its version. |
3.1.2. Maven
Maven users can inherit from the spring-boot-starter-parent
project to obtain sensible
defaults. The parent project provides the following features:
-
Java 1.8 as the default compiler level.
-
UTF-8 source encoding.
-
A Dependency Management section, inherited from the spring-boot-dependencies pom, that manages the versions of common dependencies. This dependency management lets you omit <version> tags for those dependencies when used in your own pom.
-
An execution of the
repackage
goal with arepackage
execution id. -
Sensible resource filtering.
-
Sensible plugin configuration (exec plugin, Git commit ID, and shade).
-
Sensible resource filtering for
application.properties
andapplication.yml
including profile-specific files (for example,application-dev.properties
andapplication-dev.yml
)
Note that, since the application.properties
and application.yml
files accept Spring
style placeholders (${…}
), the Maven filtering is changed to use @..@
placeholders.
(You can override that by setting a Maven property called resource.delimiter
.)
Inheriting the Starter Parent
To configure your project to inherit from the spring-boot-starter-parent
, set the
parent
as follows:
<!-- Inherit defaults from Spring Boot -->
<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>2.2.0.M5</version>
</parent>
You should need to specify only the Spring Boot version number on this dependency. If you import additional starters, you can safely omit the version number. |
With that setup, you can also override individual dependencies by overriding a property
in your own project. For instance, to upgrade to another Spring Data release train, you
would add the following to your pom.xml
:
<properties>
<spring-data-releasetrain.version>Fowler-SR2</spring-data-releasetrain.version>
</properties>
Check the
spring-boot-dependencies pom
for a list of supported properties.
|
Using Spring Boot without the Parent POM
Not everyone likes inheriting from the spring-boot-starter-parent
POM. You may have
your own corporate standard parent that you need to use or you may prefer to explicitly
declare all your Maven configuration.
If you do not want to use the spring-boot-starter-parent
, you can still keep the
benefit of the dependency management (but not the plugin management) by using a
scope=import
dependency, as follows:
<dependencyManagement>
<dependencies>
<dependency>
<!-- Import dependency management from Spring Boot -->
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-dependencies</artifactId>
<version>2.2.0.M5</version>
<type>pom</type>
<scope>import</scope>
</dependency>
</dependencies>
</dependencyManagement>
The preceding sample setup does not let you override individual dependencies by using a
property, as explained above. To achieve the same result, you need to add an entry in the
dependencyManagement
of your project before the spring-boot-dependencies
entry.
For instance, to upgrade to another Spring Data release train, you could add the
following element to your pom.xml
:
<dependencyManagement>
<dependencies>
<!-- Override Spring Data release train provided by Spring Boot -->
<dependency>
<groupId>org.springframework.data</groupId>
<artifactId>spring-data-releasetrain</artifactId>
<version>Fowler-SR2</version>
<type>pom</type>
<scope>import</scope>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-dependencies</artifactId>
<version>2.2.0.M5</version>
<type>pom</type>
<scope>import</scope>
</dependency>
</dependencies>
</dependencyManagement>
In the preceding example, we specify a BOM, but any dependency type can be overridden in the same way. |
Using the Spring Boot Maven Plugin
Spring Boot includes a Maven
plugin that can package the project as an executable jar. Add the plugin to your
<plugins>
section if you want to use it, as shown in the following example:
<build>
<plugins>
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
</plugin>
</plugins>
</build>
If you use the Spring Boot starter parent pom, you need to add only the plugin. There is no need to configure it unless you want to change the settings defined in the parent. |
3.1.3. Gradle
To learn about using Spring Boot with Gradle, please refer to the documentation for Spring Boot’s Gradle plugin:
3.1.4. Ant
It is possible to build a Spring Boot project using Apache Ant+Ivy. The
spring-boot-antlib
“AntLib” module is also available to help Ant create executable
jars.
To declare dependencies, a typical ivy.xml
file looks something like the following
example:
<ivy-module version="2.0">
<info organisation="org.springframework.boot" module="spring-boot-sample-ant" />
<configurations>
<conf name="compile" description="everything needed to compile this module" />
<conf name="runtime" extends="compile" description="everything needed to run this module" />
</configurations>
<dependencies>
<dependency org="org.springframework.boot" name="spring-boot-starter"
rev="${spring-boot.version}" conf="compile" />
</dependencies>
</ivy-module>
A typical build.xml
looks like the following example:
<project
xmlns:ivy="antlib:org.apache.ivy.ant"
xmlns:spring-boot="antlib:org.springframework.boot.ant"
name="myapp" default="build">
<property name="spring-boot.version" value="2.2.0.M5" />
<target name="resolve" description="--> retrieve dependencies with ivy">
<ivy:retrieve pattern="lib/[conf]/[artifact]-[type]-[revision].[ext]" />
</target>
<target name="classpaths" depends="resolve">
<path id="compile.classpath">
<fileset dir="lib/compile" includes="*.jar" />
</path>
</target>
<target name="init" depends="classpaths">
<mkdir dir="build/classes" />
</target>
<target name="compile" depends="init" description="compile">
<javac srcdir="src/main/java" destdir="build/classes" classpathref="compile.classpath" />
</target>
<target name="build" depends="compile">
<spring-boot:exejar destfile="build/myapp.jar" classes="build/classes">
<spring-boot:lib>
<fileset dir="lib/runtime" />
</spring-boot:lib>
</spring-boot:exejar>
</target>
</project>
If you do not want to use the spring-boot-antlib module, see the
Build an Executable Archive from Ant without Using spring-boot-antlib “How-to” .
|
3.1.5. Starters
Starters are a set of convenient dependency descriptors that you can include in your
application. You get a one-stop shop for all the Spring and related technologies that you
need without having to hunt through sample code and copy-paste loads of dependency
descriptors. For example, if you want to get started using Spring and JPA for database
access, include the spring-boot-starter-data-jpa
dependency in your project.
The starters contain a lot of the dependencies that you need to get a project up and running quickly and with a consistent, supported set of managed transitive dependencies.
The following application starters are provided by Spring Boot under the
org.springframework.boot
group:
Name | Description | Pom |
---|---|---|
Core starter, including auto-configuration support, logging and YAML |
||
Starter for JMS messaging using Apache ActiveMQ |
||
Starter for using Spring AMQP and Rabbit MQ |
||
Starter for aspect-oriented programming with Spring AOP and AspectJ |
||
Starter for JMS messaging using Apache Artemis |
||
Starter for using Spring Batch |
||
Starter for using Spring Framework’s caching support |
||
Starter for using Spring Cloud Connectors which simplifies connecting to services in cloud platforms like Cloud Foundry and Heroku |
||
Starter for using Cassandra distributed database and Spring Data Cassandra |
||
Starter for using Cassandra distributed database and Spring Data Cassandra Reactive |
||
Starter for using Couchbase document-oriented database and Spring Data Couchbase |
||
Starter for using Couchbase document-oriented database and Spring Data Couchbase Reactive |
||
Starter for using Elasticsearch search and analytics engine and Spring Data Elasticsearch |
||
Starter for using Spring Data JDBC |
||
Starter for using Spring Data JPA with Hibernate |
||
Starter for using Spring Data LDAP |
||
Starter for using MongoDB document-oriented database and Spring Data MongoDB |
||
Starter for using MongoDB document-oriented database and Spring Data MongoDB Reactive |
||
Starter for using Neo4j graph database and Spring Data Neo4j |
||
Starter for using Redis key-value data store with Spring Data Redis and the Lettuce client |
||
Starter for using Redis key-value data store with Spring Data Redis reactive and the Lettuce client |
||
Starter for exposing Spring Data repositories over REST using Spring Data REST |
||
Starter for using the Apache Solr search platform with Spring Data Solr |
||
Starter for building MVC web applications using FreeMarker views |
||
Starter for building MVC web applications using Groovy Templates views |
||
Starter for building hypermedia-based RESTful web application with Spring MVC and Spring HATEOAS |
||
Starter for using Spring Integration |
||
Starter for using JDBC with the HikariCP connection pool |
||
Starter for building RESTful web applications using JAX-RS and Jersey. An alternative to |
||
Starter for using jOOQ to access SQL databases. An alternative to |
||
Starter for reading and writing json |
||
Starter for JTA transactions using Atomikos |
||
Starter for JTA transactions using Bitronix |
||
Starter for using Java Mail and Spring Framework’s email sending support |
||
Starter for building web applications using Mustache views |
||
Starter for using Spring Security’s OAuth2/OpenID Connect client features |
||
Starter for using Spring Security’s OAuth2 resource server features |
||
Starter for using the Quartz scheduler |
||
Starter for building RSocket clients and servers. |
||
Starter for using Spring Security |
||
Starter for testing Spring Boot applications with libraries including JUnit, Hamcrest and Mockito |
||
Starter for building MVC web applications using Thymeleaf views |
||
Starter for using Java Bean Validation with Hibernate Validator |
||
Starter for building web, including RESTful, applications using Spring MVC. Uses Tomcat as the default embedded container |
||
Starter for using Spring Web Services |
||
Starter for building WebFlux applications using Spring Framework’s Reactive Web support |
||
Starter for building WebSocket applications using Spring Framework’s WebSocket support |
In addition to the application starters, the following starters can be used to add production ready features:
Name | Description | Pom |
---|---|---|
Starter for using Spring Boot’s Actuator which provides production ready features to help you monitor and manage your application |
Finally, Spring Boot also includes the following starters that can be used if you want to exclude or swap specific technical facets:
Name | Description | Pom |
---|---|---|
Starter for using Jetty as the embedded servlet container. An alternative to |
||
Starter for using Log4j2 for logging. An alternative to |
||
Starter for logging using Logback. Default logging starter |
||
Starter for using Reactor Netty as the embedded reactive HTTP server. |
||
Starter for using Tomcat as the embedded servlet container. Default servlet container starter used by |
||
Starter for using Undertow as the embedded servlet container. An alternative to |
For a list of additional community contributed starters, see the
README file in
the spring-boot-starters module on GitHub.
|
3.2. Structuring Your Code
Spring Boot does not require any specific code layout to work. However, there are some best practices that help.
3.2.1. Using the “default” Package
When a class does not include a package
declaration, it is considered to be in the
“default package”. The use of the “default package” is generally discouraged and
should be avoided. It can cause particular problems for Spring Boot applications that use
the @ComponentScan
, @ConfigurationPropertiesScan
, @EntityScan
, or @SpringBootApplication
annotations, since every class from every jar is read.
We recommend that you follow Java’s recommended package naming conventions and use a
reversed domain name (for example, com.example.project ).
|
3.2.2. Locating the Main Application Class
We generally recommend that you locate your main application class in a root package
above other classes. The @SpringBootApplication
annotation is often placed on your main class, and it
implicitly defines a base “search package” for certain items. For example, if you are
writing a JPA application, the package of the @SpringBootApplication
annotated class
is used to search for @Entity
items. Using a root package also allows component
scan to apply only on your project.
If you don’t want to use @SpringBootApplication , the @EnableAutoConfiguration
@ComponentScan , and @ConfigurationPropertiesScan annotations that it imports defines
that behaviour so you can also use those instead.
|
The following listing shows a typical layout:
com +- example +- myapplication +- Application.java | +- customer | +- Customer.java | +- CustomerController.java | +- CustomerService.java | +- CustomerRepository.java | +- order +- Order.java +- OrderController.java +- OrderService.java +- OrderRepository.java
The Application.java
file would declare the main
method, along with the basic
@SpringBootApplication
, as follows:
package com.example.myapplication;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
@SpringBootApplication
public class Application {
public static void main(String[] args) {
SpringApplication.run(Application.class, args);
}
}
3.3. Configuration Classes
Spring Boot favors Java-based configuration. Although it is possible to use
SpringApplication
with XML sources, we generally recommend that your primary source be
a single @Configuration
class. Usually the class that defines the main
method is a
good candidate as the primary @Configuration
.
Many Spring configuration examples have been published on the Internet that use XML
configuration. If possible, always try to use the equivalent Java-based configuration.
Searching for Enable* annotations can be a good starting point.
|
3.3.1. Importing Additional Configuration Classes
You need not put all your @Configuration
into a single class. The @Import
annotation
can be used to import additional configuration classes. Alternatively, you can use
@ComponentScan
to automatically pick up all Spring components, including
@Configuration
classes.
3.4. Auto-configuration
Spring Boot auto-configuration attempts to automatically configure your Spring
application based on the jar dependencies that you have added. For example, if HSQLDB
is on your classpath, and you have not manually configured any database connection beans,
then Spring Boot auto-configures an in-memory database.
You need to opt-in to auto-configuration by adding the @EnableAutoConfiguration
or
@SpringBootApplication
annotations to one of your @Configuration
classes.
You should only ever add one @SpringBootApplication or @EnableAutoConfiguration
annotation. We generally recommend that you add one or the other to your primary
@Configuration class only.
|
3.4.1. Gradually Replacing Auto-configuration
Auto-configuration is non-invasive. At any point, you can start to define your own
configuration to replace specific parts of the auto-configuration. For example, if you
add your own DataSource
bean, the default embedded database support backs away.
If you need to find out what auto-configuration is currently being applied, and why,
start your application with the --debug
switch. Doing so enables debug logs for a
selection of core loggers and logs a conditions report to the console.
3.4.2. Disabling Specific Auto-configuration Classes
If you find that specific auto-configuration classes that you do not want are being
applied, you can use the exclude attribute of @EnableAutoConfiguration
to disable them,
as shown in the following example:
import org.springframework.boot.autoconfigure.*;
import org.springframework.boot.autoconfigure.jdbc.*;
import org.springframework.context.annotation.*;
@Configuration(proxyBeanMethods = false)
@EnableAutoConfiguration(exclude={DataSourceAutoConfiguration.class})
public class MyConfiguration {
}
If the class is not on the classpath, you can use the excludeName
attribute of the
annotation and specify the fully qualified name instead. Finally, you can also control
the list of auto-configuration classes to exclude by using the
spring.autoconfigure.exclude
property.
You can define exclusions both at the annotation level and by using the property. |
3.5. Spring Beans and Dependency Injection
You are free to use any of the standard Spring Framework techniques to define your beans
and their injected dependencies. For simplicity, we often find that using
@ComponentScan
(to find your beans) and using @Autowired
(to do constructor
injection) works well.
If you structure your code as suggested above (locating your application class in a root
package), you can add @ComponentScan
without any arguments. All of your application
components (@Component
, @Service
, @Repository
, @Controller
etc.) are
automatically registered as Spring Beans.
The following example shows a @Service
Bean that uses constructor injection to obtain a
required RiskAssessor
bean:
package com.example.service;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
@Service
public class DatabaseAccountService implements AccountService {
private final RiskAssessor riskAssessor;
@Autowired
public DatabaseAccountService(RiskAssessor riskAssessor) {
this.riskAssessor = riskAssessor;
}
// ...
}
If a bean has one constructor, you can omit the @Autowired
, as shown in the following
example:
@Service
public class DatabaseAccountService implements AccountService {
private final RiskAssessor riskAssessor;
public DatabaseAccountService(RiskAssessor riskAssessor) {
this.riskAssessor = riskAssessor;
}
// ...
}
Notice how using constructor injection lets the riskAssessor field be marked as
final , indicating that it cannot be subsequently changed.
|
3.6. Using the @SpringBootApplication Annotation
Many Spring Boot developers like their apps to use auto-configuration, component scan and
be able to define extra configuration on their "application class". A single
@SpringBootApplication
annotation can be used to enable those three features, that is:
-
@EnableAutoConfiguration
: enable Spring Boot’s auto-configuration mechanism -
@ComponentScan
: enable@Component
scan on the package where the application is located (see the best practices) -
@ConfigurationPropertiesScan
: enable@ConfigurationProperties
scan on the package where the application is located (see the best practices) -
@Configuration
: allow to register extra beans in the context or import additional configuration classes
package com.example.myapplication;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
@SpringBootApplication // same as @Configuration @EnableAutoConfiguration @ComponentScan @ConfigurationPropertiesScan
public class Application {
public static void main(String[] args) {
SpringApplication.run(Application.class, args);
}
}
@SpringBootApplication also provides aliases to customize the attributes of
@EnableAutoConfiguration and @ComponentScan .
|
None of these features are mandatory and you may choose to replace this single annotation by any of the features that it enables. For instance, you may not want to use component scan or configuration properties scan in your application:
In this example, |
3.7. Running Your Application
One of the biggest advantages of packaging your application as a jar and using an embedded HTTP server is that you can run your application as you would any other. Debugging Spring Boot applications is also easy. You do not need any special IDE plugins or extensions.
This section only covers jar based packaging. If you choose to package your application as a war file, you should refer to your server and IDE documentation. |
3.7.1. Running from an IDE
You can run a Spring Boot application from your IDE as a simple Java application.
However, you first need to import your project. Import steps vary depending on your IDE
and build system. Most IDEs can import Maven projects directly. For example, Eclipse
users can select Import…
→ Existing Maven Projects
from the File
menu.
If you cannot directly import your project into your IDE, you may be able to generate IDE metadata by using a build plugin. Maven includes plugins for Eclipse and IDEA. Gradle offers plugins for various IDEs.
If you accidentally run a web application twice, you see a “Port already in use”
error. STS users can use the Relaunch button rather than the Run button to ensure
that any existing instance is closed.
|
3.7.2. Running as a Packaged Application
If you use the Spring Boot Maven or Gradle plugins to create an executable jar, you can
run your application using java -jar
, as shown in the following example:
$ java -jar target/myapplication-0.0.1-SNAPSHOT.jar
It is also possible to run a packaged application with remote debugging support enabled. Doing so lets you attach a debugger to your packaged application, as shown in the following example:
$ java -Xdebug -Xrunjdwp:server=y,transport=dt_socket,address=8000,suspend=n \ -jar target/myapplication-0.0.1-SNAPSHOT.jar
3.7.3. Using the Maven Plugin
The Spring Boot Maven plugin includes a run
goal that can be used to quickly compile
and run your application. Applications run in an exploded form, as they do in your IDE.
The following example shows a typical Maven command to run a Spring Boot application:
$ mvn spring-boot:run
You might also want to use the MAVEN_OPTS
operating system environment variable, as
shown in the following example:
$ export MAVEN_OPTS=-Xmx1024m
3.7.4. Using the Gradle Plugin
The Spring Boot Gradle plugin also includes a bootRun
task that can be used to run your
application in an exploded form. The bootRun
task is added whenever you apply the
org.springframework.boot
and java
plugins and is shown in the following example:
$ gradle bootRun
You might also want to use the JAVA_OPTS
operating system environment variable, as
shown in the following example:
$ export JAVA_OPTS=-Xmx1024m
3.7.5. Hot Swapping
Since Spring Boot applications are just plain Java applications, JVM hot-swapping should work out of the box. JVM hot swapping is somewhat limited with the bytecode that it can replace. For a more complete solution, JRebel can be used.
The
spring-boot-devtools
module also includes support for quick application restarts.
See the Developer Tools section later in this chapter and the
Hot swapping “How-to” for details.
3.8. Developer Tools
Spring Boot includes an additional set of tools that can make the application
development experience a little more pleasant. The spring-boot-devtools
module can be
included in any project to provide additional development-time features. To include
devtools support, add the module dependency to your build, as shown in the following
listings for Maven and Gradle:
<dependencies>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-devtools</artifactId>
<optional>true</optional>
</dependency>
</dependencies>
configurations {
developmentOnly
runtimeClasspath {
extendsFrom developmentOnly
}
}
dependencies {
developmentOnly("org.springframework.boot:spring-boot-devtools")
}
Developer tools are automatically disabled when running a fully packaged
application. If your application is launched from java -jar or if it is started from a
special classloader, then it is considered a “production application”. If that does not
apply to you (i.e. if you run your application from a container), consider excluding
devtools or set the -Dspring.devtools.restart.enabled=false system property.
|
Flagging the dependency as optional in Maven or using a custom developmentOnly
configuration in Gradle (as shown above) is a best practice that prevents devtools from
being transitively applied to other modules that use your project.
|
Repackaged archives do not contain devtools by default. If you want to use a
certain remote devtools feature, you need to disable the
excludeDevtools build property to include it. The property is supported with both the
Maven and Gradle plugins.
|
3.8.1. Property Defaults
Several of the libraries supported by Spring Boot use caches to improve performance. For example, template engines cache compiled templates to avoid repeatedly parsing template files. Also, Spring MVC can add HTTP caching headers to responses when serving static resources.
While caching is very beneficial in production, it can be counter-productive during development, preventing you from seeing the changes you just made in your application. For this reason, spring-boot-devtools disables the caching options by default.
Cache options are usually configured by settings in your application.properties
file.
For example, Thymeleaf offers the spring.thymeleaf.cache
property. Rather than needing
to set these properties manually, the spring-boot-devtools
module automatically applies
sensible development-time configuration.
Because you need more information about web requests while developing Spring MVC and
Spring WebFlux applications, developer tools will enable DEBUG
logging for the web
logging group. This will give you information about the incoming request, which handler is
processing it, the response outcome, etc. If you wish to log all request details
(including potentially sensitive information), you can turn on the
spring.http.log-request-details
configuration property.
If you don’t want property defaults to be applied you can set
spring.devtools.add-properties to false in your application.properties .
|
For a complete list of the properties that are applied by the devtools, see DevToolsPropertyDefaultsPostProcessor. |
3.8.2. Automatic Restart
Applications that use spring-boot-devtools
automatically restart whenever files on the
classpath change. This can be a useful feature when working in an IDE, as it gives a very
fast feedback loop for code changes. By default, any entry on the classpath that points
to a folder is monitored for changes. Note that certain resources, such as static assets
and view templates, do not need to restart the
application.
As long as forking is enabled, you can also start your application by using the supported build plugins (Maven and Gradle), since DevTools needs an isolated application classloader to operate properly. By default, the Gradle and Maven plugins fork the application process. |
Automatic restart works very well when used with LiveReload. See the LiveReload section for details. If you use JRebel, automatic restarts are disabled in favor of dynamic class reloading. Other devtools features (such as LiveReload and property overrides) can still be used. |
DevTools relies on the application context’s shutdown hook to close it during a
restart. It does not work correctly if you have disabled the shutdown hook
(SpringApplication.setRegisterShutdownHook(false) ).
|
When deciding if an entry on the classpath should trigger a restart when it
changes, DevTools automatically ignores projects named spring-boot ,
spring-boot-devtools , spring-boot-autoconfigure , spring-boot-actuator , and
spring-boot-starter .
|
DevTools needs to customize the ResourceLoader used by the ApplicationContext .
If your application provides one already, it is going to be wrapped. Direct override of
the getResource method on the ApplicationContext is not supported.
|
Logging changes in condition evaluation
By default, each time your application restarts, a report showing the condition evaluation delta is logged. The report shows the changes to your application’s auto-configuration as you make changes such as adding or removing beans and setting configuration properties.
To disable the logging of the report, set the following property:
spring.devtools.restart.log-condition-evaluation-delta=false
Excluding Resources
Certain resources do not necessarily need to trigger a restart when they are changed. For
example, Thymeleaf templates can be edited in-place. By default, changing resources
in /META-INF/maven
, /META-INF/resources
, /resources
, /static
, /public
, or
/templates
does not trigger a restart but does trigger a
live reload. If you want to customize these
exclusions, you can use the spring.devtools.restart.exclude
property. For example, to
exclude only /static
and /public
you would set the following property:
spring.devtools.restart.exclude=static/**,public/**
If you want to keep those defaults and add additional exclusions, use the
spring.devtools.restart.additional-exclude property instead.
|
Watching Additional Paths
You may want your application to be restarted or reloaded when you make changes to files
that are not on the classpath. To do so, use the
spring.devtools.restart.additional-paths
property to configure additional paths to
watch for changes. You can use the spring.devtools.restart.exclude
property
described earlier to control whether changes
beneath the additional paths trigger a full restart or a
live reload.
Disabling Restart
If you do not want to use the restart feature, you can disable it by using the
spring.devtools.restart.enabled
property. In most cases, you can set this property in
your application.properties
(doing so still initializes the restart classloader, but it
does not watch for file changes).
If you need to completely disable restart support (for example, because it does not work
with a specific library), you need to set the spring.devtools.restart.enabled
System
property to false
before calling SpringApplication.run(…)
, as shown in the
following example:
public static void main(String[] args) {
System.setProperty("spring.devtools.restart.enabled", "false");
SpringApplication.run(MyApp.class, args);
}
Using a Trigger File
If you work with an IDE that continuously compiles changed files, you might prefer to trigger restarts only at specific times. To do so, you can use a “trigger file”, which is a special file that must be modified when you want to actually trigger a restart check. Changing the file only triggers the check and the restart only occurs if Devtools has detected it has to do something. The trigger file can be updated manually or with an IDE plugin.
To use a trigger file, set the spring.devtools.restart.trigger-file
property to the
path of your trigger file.
You might want to set spring.devtools.restart.trigger-file as a
global setting, so that all your projects behave
in the same way.
|
Customizing the Restart Classloader
As described earlier in the Restart vs Reload section, restart functionality is implemented by using two classloaders. For most applications, this approach works well. However, it can sometimes cause classloading issues.
By default, any open project in your IDE is loaded with the “restart” classloader, and
any regular .jar
file is loaded with the “base” classloader. If you work on a
multi-module project, and not every module is imported into your IDE, you may need to
customize things. To do so, you can create a META-INF/spring-devtools.properties
file.
The spring-devtools.properties
file can contain properties prefixed with
restart.exclude
and restart.include
. The include
elements are items that should be
pulled up into the “restart” classloader, and the exclude
elements are items that
should be pushed down into the “base” classloader. The value of the property is a regex
pattern that is applied to the classpath, as shown in the following example:
restart.exclude.companycommonlibs=/mycorp-common-[\\w\\d-\.]+\.jar
restart.include.projectcommon=/mycorp-myproj-[\\w\\d-\.]+\.jar
All property keys must be unique. As long as a property starts with
restart.include. or restart.exclude. it is considered.
|
All META-INF/spring-devtools.properties from the classpath are loaded. You can
package files inside your project, or in the libraries that the project consumes.
|
Known Limitations
Restart functionality does not work well with objects that are deserialized by using a
standard ObjectInputStream
. If you need to deserialize data, you may need to use
Spring’s ConfigurableObjectInputStream
in combination with
Thread.currentThread().getContextClassLoader()
.
Unfortunately, several third-party libraries deserialize without considering the context classloader. If you find such a problem, you need to request a fix with the original authors.
3.8.3. LiveReload
The spring-boot-devtools
module includes an embedded LiveReload server that can be used
to trigger a browser refresh when a resource is changed. LiveReload browser extensions
are freely available for Chrome, Firefox and Safari from
livereload.com.
If you do not want to start the LiveReload server when your application runs, you can set
the spring.devtools.livereload.enabled
property to false
.
You can only run one LiveReload server at a time. Before starting your application, ensure that no other LiveReload servers are running. If you start multiple applications from your IDE, only the first has LiveReload support. |
3.8.4. Global Settings
You can configure global devtools settings by adding a file named
.spring-boot-devtools.properties
to your $HOME
folder (note that the filename starts
with “.”). Any properties added to this file apply to all Spring Boot applications on
your machine that use devtools. For example, to configure restart to always use a
trigger file, you would add the following
property:
spring.devtools.reload.trigger-file=.reloadtrigger
Profiles activated in .spring-boot-devtools.properties will not affect the
loading of profile-specific configuration files.
|
3.8.5. Remote Applications
The Spring Boot developer tools are not limited to local development. You can also
use several features when running applications remotely. Remote support is opt-in. To
enable it, you need to make sure that devtools
is included in the repackaged archive,
as shown in the following listing:
<build>
<plugins>
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
<configuration>
<excludeDevtools>false</excludeDevtools>
</configuration>
</plugin>
</plugins>
</build>
Then you need to set a spring.devtools.remote.secret
property, as shown in the
following example:
spring.devtools.remote.secret=mysecret
Enabling spring-boot-devtools on a remote application is a security risk. You
should never enable support on a production deployment.
|
Remote devtools support is provided in two parts: a server-side endpoint that accepts
connections and a client application that you run in your IDE. The server component is
automatically enabled when the spring.devtools.remote.secret
property is set. The
client component must be launched manually.
Running the Remote Client Application
The remote client application is designed to be run from within your IDE. You need to run
org.springframework.boot.devtools.RemoteSpringApplication
with the same classpath as
the remote project that you connect to. The application’s single required argument is the
remote URL to which it connects.
For example, if you are using Eclipse or STS and you have a project named my-app
that
you have deployed to Cloud Foundry, you would do the following:
-
Select
Run Configurations…
from theRun
menu. -
Create a new
Java Application
“launch configuration”. -
Browse for the
my-app
project. -
Use
org.springframework.boot.devtools.RemoteSpringApplication
as the main class. -
Add
https://myapp.cfapps.io
to theProgram arguments
(or whatever your remote URL is).
A running remote client might resemble the following listing:
. ____ _ __ _ _ /\\ / ___'_ __ _ _(_)_ __ __ _ ___ _ \ \ \ \ ( ( )\___ | '_ | '_| | '_ \/ _` | | _ \___ _ __ ___| |_ ___ \ \ \ \ \\/ ___)| |_)| | | | | || (_| []::::::[] / -_) ' \/ _ \ _/ -_) ) ) ) ) ' |____| .__|_| |_|_| |_\__, | |_|_\___|_|_|_\___/\__\___|/ / / / =========|_|==============|___/===================================/_/_/_/ :: Spring Boot Remote :: 2.2.0.M5 2015-06-10 18:25:06.632 INFO 14938 --- [ main] o.s.b.devtools.RemoteSpringApplication : Starting RemoteSpringApplication on pwmbp with PID 14938 (/Users/pwebb/projects/spring-boot/code/spring-boot-devtools/target/classes started by pwebb in /Users/pwebb/projects/spring-boot/code/spring-boot-samples/spring-boot-sample-devtools) 2015-06-10 18:25:06.671 INFO 14938 --- [ main] s.c.a.AnnotationConfigApplicationContext : Refreshing org.springframework.context.annotation.AnnotationConfigApplicationContext@2a17b7b6: startup date [Wed Jun 10 18:25:06 PDT 2015]; root of context hierarchy 2015-06-10 18:25:07.043 WARN 14938 --- [ main] o.s.b.d.r.c.RemoteClientConfiguration : The connection to http://localhost:8080 is insecure. You should use a URL starting with 'https://'. 2015-06-10 18:25:07.074 INFO 14938 --- [ main] o.s.b.d.a.OptionalLiveReloadServer : LiveReload server is running on port 35729 2015-06-10 18:25:07.130 INFO 14938 --- [ main] o.s.b.devtools.RemoteSpringApplication : Started RemoteSpringApplication in 0.74 seconds (JVM running for 1.105)
Because the remote client is using the same classpath as the real application it
can directly read application properties. This is how the spring.devtools.remote.secret
property is read and passed to the server for authentication.
|
It is always advisable to use https:// as the connection protocol, so that traffic
is encrypted and passwords cannot be intercepted.
|
If you need to use a proxy to access the remote application, configure the
spring.devtools.remote.proxy.host and spring.devtools.remote.proxy.port properties.
|
Remote Update
The remote client monitors your application classpath for changes in the same way as the local restart. Any updated resource is pushed to the remote application and (if required) triggers a restart. This can be helpful if you iterate on a feature that uses a cloud service that you do not have locally. Generally, remote updates and restarts are much quicker than a full rebuild and deploy cycle.
Files are only monitored when the remote client is running. If you change a file before starting the remote client, it is not pushed to the remote server. |
3.9. Packaging Your Application for Production
Executable jars can be used for production deployment. As they are self-contained, they are also ideally suited for cloud-based deployment.
For additional “production ready” features, such as health, auditing, and metric REST
or JMX end-points, consider adding spring-boot-actuator
. See
Spring Boot Actuator: Production-ready Features for details.
3.10. What to Read Next
You should now understand how you can use Spring Boot and some best practices that you should follow. You can now go on to learn about specific Spring Boot features in depth, or you could skip ahead and read about the “production ready” aspects of Spring Boot.
4. Spring Boot Features
This section dives into the details of Spring Boot. Here you can learn about the key features that you may want to use and customize. If you have not already done so, you might want to read the "Getting Started" and "Using Spring Boot" sections, so that you have a good grounding of the basics.
4.1. SpringApplication
The SpringApplication
class provides a convenient way to bootstrap a Spring application
that is started from a main()
method. In many situations, you can delegate to the
static SpringApplication.run
method, as shown in the following example:
public static void main(String[] args) {
SpringApplication.run(MySpringConfiguration.class, args);
}
When your application starts, you should see something similar to the following output:
. ____ _ __ _ _ /\\ / ___'_ __ _ _(_)_ __ __ _ \ \ \ \ ( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \ \\/ ___)| |_)| | | | | || (_| | ) ) ) ) ' |____| .__|_| |_|_| |_\__, | / / / / =========|_|==============|___/=/_/_/_/ :: Spring Boot :: v2.2.0.M5 2013-07-31 00:08:16.117 INFO 56603 --- [ main] o.s.b.s.app.SampleApplication : Starting SampleApplication v0.1.0 on mycomputer with PID 56603 (/apps/myapp.jar started by pwebb) 2013-07-31 00:08:16.166 INFO 56603 --- [ main] ationConfigServletWebServerApplicationContext : Refreshing org.springframework.boot.web.servlet.context.AnnotationConfigServletWebServerApplicationContext@6e5a8246: startup date [Wed Jul 31 00:08:16 PDT 2013]; root of context hierarchy 2014-03-04 13:09:54.912 INFO 41370 --- [ main] .t.TomcatServletWebServerFactory : Server initialized with port: 8080 2014-03-04 13:09:56.501 INFO 41370 --- [ main] o.s.b.s.app.SampleApplication : Started SampleApplication in 2.992 seconds (JVM running for 3.658)
By default, INFO
logging messages are shown, including some relevant startup details,
such as the user that launched the application. If you need a log level other than INFO
,
you can set it, as described in Log Levels,
4.1.1. Startup Failure
If your application fails to start, registered FailureAnalyzers
get a chance to provide
a dedicated error message and a concrete action to fix the problem. For instance, if you
start a web application on port 8080
and that port is already in use, you should see
something similar to the following message:
*************************** APPLICATION FAILED TO START *************************** Description: Embedded servlet container failed to start. Port 8080 was already in use. Action: Identify and stop the process that's listening on port 8080 or configure this application to listen on another port.
Spring Boot provides numerous FailureAnalyzer implementations, and you can
add your own.
|
If no failure analyzers are able to handle the exception, you can still display the full
conditions report to better understand what went wrong. To do so, you need to
enable the debug
property or
enable DEBUG
logging for
org.springframework.boot.autoconfigure.logging.ConditionEvaluationReportLoggingListener
.
For instance, if you are running your application by using java -jar
, you can enable
the debug
property as follows:
$ java -jar myproject-0.0.1-SNAPSHOT.jar --debug
4.1.2. Lazy Initialization
SpringApplication
allows an application to be initialized lazily. When lazy
initialization is enabled, beans are created as they are needed rather than during
application startup. As a result, enabling lazy initialization can reduce the time that
it takes your application to start. In a web application, enabling lazy initialization
will result in many web-related beans not being initialized until an HTTP request is
received.
A downside of lazy initialization is that it can delay the discovery of a problem with the application. If a misconfigured bean is initialized lazily, a failure will no longer occur during startup and the problem will only become apparent when the bean is initialized. Care must also be taken to ensure that the JVM has sufficient memory to accommodate all of the application’s beans and not just those that are initialized during startup. For these reasons, lazy initialization is not enabled by default and it is recommended that fine-tuning of the JVM’s heap size is done before enabling lazy initialization.
Lazy initialization can be enabled programatically using the lazyInitialization
method
on SpringApplicationBuilder
or the setLazyInitialization
method on
SpringApplication
. Alternatively, it can be enabled using the
spring.main.lazy-initialization
property as shown in the following example:
spring.main.lazy-initialization=true
If you want to disable lazy initialization for certain beans while using lazy
initialization for the rest of the application, you can explicitly set their lazy attribute
to false using the @Lazy(false) annotation.
|
4.1.3. Customizing the Banner
The banner that is printed on start up can be changed by adding a banner.txt
file to
your classpath or by setting the spring.banner.location
property to the location of such
a file. If the file has an encoding other than UTF-8, you can set spring.banner.charset
.
In addition to a text file, you can also add a banner.gif
, banner.jpg
, or banner.png
image file to your classpath or set the spring.banner.image.location
property. Images
are converted into an ASCII art representation and printed above any text banner.
Inside your banner.txt
file, you can use any of the following placeholders:
Variable | Description |
---|---|
|
The version number of your application, as declared in |
|
The version number of your application, as declared in |
|
The Spring Boot version that you are using. For example |
|
The Spring Boot version that you are using, formatted for display (surrounded with
brackets and prefixed with |
|
Where |
|
The title of your application, as declared in |
The SpringApplication.setBanner(…) method can be used if you want to generate
a banner programmatically. Use the org.springframework.boot.Banner interface and
implement your own printBanner() method.
|
You can also use the spring.main.banner-mode
property to determine if the banner has
to be printed on System.out
(console
), sent to the configured logger (log
), or not
produced at all (off
).
The printed banner is registered as a singleton bean under the following name:
springBootBanner
.
4.1.4. Customizing SpringApplication
If the SpringApplication
defaults are not to your taste, you can instead create a local
instance and customize it. For example, to turn off the banner, you could write:
public static void main(String[] args) {
SpringApplication app = new SpringApplication(MySpringConfiguration.class);
app.setBannerMode(Banner.Mode.OFF);
app.run(args);
}
The constructor arguments passed to SpringApplication are configuration sources
for Spring beans. In most cases, these are references to @Configuration classes, but
they could also be references to XML configuration or to packages that should be scanned.
|
It is also possible to configure the SpringApplication
by using an
application.properties
file. See Externalized Configuration for details.
For a complete list of the configuration options, see the
SpringApplication
Javadoc.
4.1.5. Fluent Builder API
If you need to build an ApplicationContext
hierarchy (multiple contexts with a
parent/child relationship) or if you prefer using a “fluent” builder API, you can
use the SpringApplicationBuilder
.
The SpringApplicationBuilder
lets you chain together multiple method calls and includes
parent
and child
methods that let you create a hierarchy, as shown in the following
example:
new SpringApplicationBuilder()
.sources(Parent.class)
.child(Application.class)
.bannerMode(Banner.Mode.OFF)
.run(args);
There are some restrictions when creating an ApplicationContext hierarchy. For
example, Web components must be contained within the child context, and the same
Environment is used for both parent and child contexts. See the
SpringApplicationBuilder
Javadoc for full details.
|
4.1.6. Application Events and Listeners
In addition to the usual Spring Framework events, such as
ContextRefreshedEvent
,
a SpringApplication
sends some additional application events.
Some events are actually triggered before the If you want those listeners to be registered automatically, regardless of the way the
application is created, you can add a org.springframework.context.ApplicationListener=com.example.project.MyListener |
Application events are sent in the following order, as your application runs:
-
An
ApplicationStartingEvent
is sent at the start of a run but before any processing, except for the registration of listeners and initializers. -
An
ApplicationEnvironmentPreparedEvent
is sent when theEnvironment
to be used in the context is known but before the context is created. -
An
ApplicationContextInitializedEvent
is sent when theApplicationContext
is prepared and ApplicationContextInitializers have been called but before any bean definitions are loaded. -
An
ApplicationPreparedEvent
is sent just before the refresh is started but after bean definitions have been loaded. -
An
ApplicationStartedEvent
is sent after the context has been refreshed but before any application and command-line runners have been called. -
An
ApplicationReadyEvent
is sent after any application and command-line runners have been called. It indicates that the application is ready to service requests. -
An
ApplicationFailedEvent
is sent if there is an exception on startup.
The above list only includes SpringApplicationEvent`s that are tied to a `SpringApplication
.
In addition to these, the following events are also published after ApplicationPreparedEvent
and before ApplicationStartedEvent
:
-
A
ContextRefreshedEvent
is sent when anApplicationContext
is refreshed. -
A
WebServerInitializedEvent
is sent after theWebServer
is ready.ServletWebServerInitializedEvent
andReactiveWebServerInitializedEvent
are the servlet and reactive variants respectively.
You often need not use application events, but it can be handy to know that they exist. Internally, Spring Boot uses events to handle a variety of tasks. |
Application events are sent by using Spring Framework’s event publishing mechanism. Part
of this mechanism ensures that an event published to the listeners in a child context is
also published to the listeners in any ancestor contexts. As a result of this, if your
application uses a hierarchy of SpringApplication
instances, a listener may receive
multiple instances of the same type of application event.
To allow your listener to distinguish between an event for its context and an event for
a descendant context, it should request that its application context is injected and then
compare the injected context with the context of the event. The context can be injected
by implementing ApplicationContextAware
or, if the listener is a bean, by using
@Autowired
.
4.1.7. Web Environment
A SpringApplication
attempts to create the right type of ApplicationContext
on your
behalf. The algorithm used to determine a WebApplicationType
is fairly simple:
-
If Spring MVC is present, an
AnnotationConfigServletWebServerApplicationContext
is used -
If Spring MVC is not present and Spring WebFlux is present, an
AnnotationConfigReactiveWebServerApplicationContext
is used -
Otherwise,
AnnotationConfigApplicationContext
is used
This means that if you are using Spring MVC and the new WebClient
from Spring WebFlux in
the same application, Spring MVC will be used by default. You can override that easily
by calling setWebApplicationType(WebApplicationType)
.
It is also possible to take complete control of the ApplicationContext
type that is
used by calling setApplicationContextClass(…)
.
It is often desirable to call setWebApplicationType(WebApplicationType.NONE) when
using SpringApplication within a JUnit test.
|
4.1.8. Accessing Application Arguments
If you need to access the application arguments that were passed to
SpringApplication.run(…)
, you can inject a
org.springframework.boot.ApplicationArguments
bean. The ApplicationArguments
interface provides access to both the raw String[]
arguments as well as parsed option
and non-option
arguments, as shown in the following example:
import org.springframework.boot.*;
import org.springframework.beans.factory.annotation.*;
import org.springframework.stereotype.*;
@Component
public class MyBean {
@Autowired
public MyBean(ApplicationArguments args) {
boolean debug = args.containsOption("debug");
List<String> files = args.getNonOptionArgs();
// if run with "--debug logfile.txt" debug=true, files=["logfile.txt"]
}
}
Spring Boot also registers a CommandLinePropertySource with the Spring
Environment . This lets you also inject single application arguments by using the
@Value annotation.
|
4.1.9. Using the ApplicationRunner or CommandLineRunner
If you need to run some specific code once the SpringApplication
has started, you can
implement the ApplicationRunner
or CommandLineRunner
interfaces. Both interfaces work
in the same way and offer a single run
method, which is called just before
SpringApplication.run(…)
completes.
The CommandLineRunner
interfaces provides access to application arguments as a simple
string array, whereas the ApplicationRunner
uses the ApplicationArguments
interface
discussed earlier. The following example shows a CommandLineRunner
with a run
method:
import org.springframework.boot.*;
import org.springframework.stereotype.*;
@Component
public class MyBean implements CommandLineRunner {
public void run(String... args) {
// Do something...
}
}
If several CommandLineRunner
or ApplicationRunner
beans are defined that must be
called in a specific order, you can additionally implement the
org.springframework.core.Ordered
interface or use the
org.springframework.core.annotation.Order
annotation.
4.1.10. Application Exit
Each SpringApplication
registers a shutdown hook with the JVM to ensure that the
ApplicationContext
closes gracefully on exit. All the standard Spring lifecycle
callbacks (such as the DisposableBean
interface or the @PreDestroy
annotation) can be
used.
In addition, beans may implement the org.springframework.boot.ExitCodeGenerator
interface if they wish to return a specific exit code when SpringApplication.exit()
is
called. This exit code can then be passed to System.exit()
to return it as a status
code, as shown in the following example:
@SpringBootApplication
public class ExitCodeApplication {
@Bean
public ExitCodeGenerator exitCodeGenerator() {
return () -> 42;
}
public static void main(String[] args) {
System.exit(SpringApplication.exit(SpringApplication.run(ExitCodeApplication.class, args)));
}
}
Also, the ExitCodeGenerator
interface may be implemented by exceptions. When such an
exception is encountered, Spring Boot returns the exit code provided by the implemented
getExitCode()
method.
4.1.11. Admin Features
It is possible to enable admin-related features for the application by specifying the
spring.application.admin.enabled
property. This exposes the
SpringApplicationAdminMXBean
on the platform MBeanServer
. You could use this feature to administer your Spring Boot
application remotely. This feature could also be useful for any service wrapper
implementation.
If you want to know on which HTTP port the application is running, get the property
with a key of local.server.port .
|
Take care when enabling this feature, as the MBean exposes a method to shutdown the application. |
4.2. Externalized Configuration
Spring Boot lets you externalize your configuration so that you can work with the same
application code in different environments. You can use properties files, YAML files,
environment variables, and command-line arguments to externalize configuration. Property
values can be injected directly into your beans by using the @Value
annotation,
accessed through Spring’s Environment
abstraction, or be
bound to structured
objects through @ConfigurationProperties
.
Spring Boot uses a very particular PropertySource
order that is designed to allow
sensible overriding of values. Properties are considered in the following order:
-
Devtools global settings properties on your home directory (
~/.spring-boot-devtools.properties
when devtools is active). -
@TestPropertySource
annotations on your tests. -
properties
attribute on your tests. Available on@SpringBootTest
and the test annotations for testing a particular slice of your application. -
Command line arguments.
-
Properties from
SPRING_APPLICATION_JSON
(inline JSON embedded in an environment variable or system property). -
ServletConfig
init parameters. -
ServletContext
init parameters. -
JNDI attributes from
java:comp/env
. -
Java System properties (
System.getProperties()
). -
OS environment variables.
-
A
RandomValuePropertySource
that has properties only inrandom.*
. -
Profile-specific application properties outside of your packaged jar (
application-{profile}.properties
and YAML variants). -
Profile-specific application properties packaged inside your jar (
application-{profile}.properties
and YAML variants). -
Application properties outside of your packaged jar (
application.properties
and YAML variants). -
Application properties packaged inside your jar (
application.properties
and YAML variants). -
@PropertySource
annotations on your@Configuration
classes. -
Default properties (specified by setting
SpringApplication.setDefaultProperties
).
To provide a concrete example, suppose you develop a @Component
that uses a name
property, as shown in the following example:
import org.springframework.stereotype.*;
import org.springframework.beans.factory.annotation.*;
@Component
public class MyBean {
@Value("${name}")
private String name;
// ...
}
On your application classpath (for example, inside your jar) you can have an
application.properties
file that provides a sensible default property value for name
.
When running in a new environment, an application.properties
file can be provided
outside of your jar that overrides the name
. For one-off testing, you can launch with a
specific command line switch (for example, java -jar app.jar --name="Spring"
).
The $ SPRING_APPLICATION_JSON='{"acme":{"name":"test"}}' java -jar myapp.jar In the preceding example, you end up with $ java -Dspring.application.json='{"name":"test"}' -jar myapp.jar You can also supply the JSON by using a command line argument, as shown in the following example: $ java -jar myapp.jar --spring.application.json='{"name":"test"}' You can also supply the JSON as a JNDI variable, as follows:
|
4.2.1. Configuring Random Values
The RandomValuePropertySource
is useful for injecting random values (for example, into
secrets or test cases). It can produce integers, longs, uuids, or strings, as shown in the
following example:
my.secret=${random.value}
my.number=${random.int}
my.bignumber=${random.long}
my.uuid=${random.uuid}
my.number.less.than.ten=${random.int(10)}
my.number.in.range=${random.int[1024,65536]}
The random.int*
syntax is OPEN value (,max) CLOSE
where the OPEN,CLOSE
are any
character and value,max
are integers. If max
is provided, then value
is the minimum
value and max
is the maximum value (exclusive).
4.2.2. Accessing Command Line Properties
By default, SpringApplication
converts any command line option arguments (that is,
arguments starting with --
, such as --server.port=9000
) to a property
and adds
them to the Spring Environment
. As mentioned previously, command line properties always
take precedence over other property sources.
If you do not want command line properties to be added to the Environment
, you can
disable them by using SpringApplication.setAddCommandLineProperties(false)
.
4.2.3. Application Property Files
SpringApplication
loads properties from application.properties
files in the following
locations and adds them to the Spring Environment
:
-
A
/config
subdirectory of the current directory -
The current directory
-
A classpath
/config
package -
The classpath root
The list is ordered by precedence (properties defined in locations higher in the list override those defined in lower locations).
You can also use YAML ('.yml') files as an alternative to '.properties'. |
If you do not like application.properties
as the configuration file name, you can
switch to another file name by specifying a spring.config.name
environment property.
You can also refer to an explicit location by using the spring.config.location
environment property (which is a comma-separated list of directory locations or file
paths). The following example shows how to specify a different file name:
$ java -jar myproject.jar --spring.config.name=myproject
The following example shows how to specify two locations:
$ java -jar myproject.jar --spring.config.location=classpath:/default.properties,classpath:/override.properties
spring.config.name and spring.config.location are used very early to
determine which files have to be loaded, so they must be defined as an environment
property (typically an OS environment variable, a system property, or a command-line
argument).
|
If spring.config.location
contains directories (as opposed to files), they should end
in /
(and, at runtime, be appended with the names generated from spring.config.name
before being loaded, including profile-specific file names). Files specified in
spring.config.location
are used as-is, with no support for profile-specific variants,
and are overridden by any profile-specific properties.
Config locations are searched in reverse order. By default, the configured locations are
classpath:/,classpath:/config/,file:./,file:./config/
. The resulting search order is
the following:
-
file:./config/
-
file:./
-
classpath:/config/
-
classpath:/
When custom config locations are configured by using spring.config.location
, they
replace the default locations. For example, if spring.config.location
is configured with
the value classpath:/custom-config/,file:./custom-config/
, the search order becomes the
following:
-
file:./custom-config/
-
classpath:custom-config/
Alternatively, when custom config locations are configured by using
spring.config.additional-location
, they are used in addition to the default locations.
Additional locations are searched before the default locations. For example, if
additional locations of classpath:/custom-config/,file:./custom-config/
are configured,
the search order becomes the following:
-
file:./custom-config/
-
classpath:custom-config/
-
file:./config/
-
file:./
-
classpath:/config/
-
classpath:/
This search ordering lets you specify default values in one configuration file and then
selectively override those values in another. You can provide default values for your
application in application.properties
(or whatever other basename you choose with
spring.config.name
) in one of the default locations. These default values can then be
overridden at runtime with a different file located in one of the custom locations.
If you use environment variables rather than system properties, most operating
systems disallow period-separated key names, but you can use underscores instead (for
example, SPRING_CONFIG_NAME instead of spring.config.name ).
|
If your application runs in a container, then JNDI properties (in java:comp/env )
or servlet context initialization parameters can be used instead of, or as well as,
environment variables or system properties.
|
4.2.4. Profile-specific Properties
In addition to application.properties
files, profile-specific properties can also be
defined by using the following naming convention: application-{profile}.properties
. The
Environment
has a set of default profiles (by default, [default]
) that are used if no
active profiles are set. In other words, if no profiles are explicitly activated, then
properties from application-default.properties
are loaded.
Profile-specific properties are loaded from the same locations as standard
application.properties
, with profile-specific files always overriding the non-specific
ones, whether or not the profile-specific files are inside or outside your
packaged jar.
If several profiles are specified, a last-wins strategy applies. For example, profiles
specified by the spring.profiles.active
property are added after those configured
through the SpringApplication
API and therefore take precedence.
If you have specified any files in spring.config.location , profile-specific
variants of those files are not considered. Use directories in
spring.config.location if you want to also use profile-specific properties.
|
4.2.5. Placeholders in Properties
The values in application.properties
are filtered through the existing Environment
when they are used, so you can refer back to previously defined values (for example, from
System properties).
app.name=MyApp
app.description=${app.name} is a Spring Boot application
You can also use this technique to create “short” variants of existing Spring Boot properties. See the Use ‘Short’ Command Line Arguments how-to for details. |
4.2.6. Encrypting Properties
Spring Boot does not provide any built in support for encrypting property values, however,
it does provide the hook points necessary to modify values contained in the Spring
Environment
. The EnvironmentPostProcessor
interface allows you to manipulate the
Environment
before the application starts. See Customize the Environment or ApplicationContext Before It Starts
for details.
If you’re looking for a secure way to store credentials and passwords, the Spring Cloud Vault project provides support for storing externalized configuration in HashiCorp Vault.
4.2.7. Using YAML Instead of Properties
YAML is a superset of JSON and, as such, is a convenient format for
specifying hierarchical configuration data. The SpringApplication
class automatically
supports YAML as an alternative to properties whenever you have the
SnakeYAML library on your classpath.
If you use “Starters”, SnakeYAML is automatically provided by
spring-boot-starter .
|
Loading YAML
Spring Framework provides two convenient classes that can be used to load YAML documents.
The YamlPropertiesFactoryBean
loads YAML as Properties
and the YamlMapFactoryBean
loads YAML as a Map
.
For example, consider the following YAML document:
environments:
dev:
url: https://dev.example.com
name: Developer Setup
prod:
url: https://another.example.com
name: My Cool App
The preceding example would be transformed into the following properties:
environments.dev.url=https://dev.example.com
environments.dev.name=Developer Setup
environments.prod.url=https://another.example.com
environments.prod.name=My Cool App
YAML lists are represented as property keys with [index]
dereferencers. For example,
consider the following YAML:
my:
servers:
- dev.example.com
- another.example.com
The preceding example would be transformed into these properties:
my.servers[0]=dev.example.com
my.servers[1]=another.example.com
To bind to properties like that by using Spring Boot’s Binder
utilities (which is what
@ConfigurationProperties
does), you need to have a property in the target bean of type
java.util.List
(or Set
) and you either need to provide a setter or initialize it with
a mutable value. For example, the following example binds to the properties shown
previously:
@ConfigurationProperties(prefix="my")
public class Config {
private List<String> servers = new ArrayList<String>();
public List<String> getServers() {
return this.servers;
}
}
Exposing YAML as Properties in the Spring Environment
The YamlPropertySourceLoader
class can be used to expose YAML as a PropertySource
in
the Spring Environment
. Doing so lets you use the @Value
annotation with placeholders
syntax to access YAML properties.
Multi-profile YAML Documents
You can specify multiple profile-specific YAML documents in a single file by using a
spring.profiles
key to indicate when the document applies, as shown in the following
example:
server:
address: 192.168.1.100
---
spring:
profiles: development
server:
address: 127.0.0.1
---
spring:
profiles: production & eu-central
server:
address: 192.168.1.120
In the preceding example, if the development
profile is active, the server.address
property is 127.0.0.1
. Similarly, if the production
and eu-central
profiles are
active, the server.address
property is 192.168.1.120
. If the development
,
production
and eu-central
profiles are not enabled, then the value for the property
is 192.168.1.100
.
|
If none are explicitly active when the application context starts, the default profiles
are activated. So, in the following YAML, we set a value for spring.security.user.password
that is available only in the "default" profile:
server:
port: 8000
---
spring:
profiles: default
security:
user:
password: weak
Whereas, in the following example, the password is always set because it is not attached to any profile, and it would have to be explicitly reset in all other profiles as necessary:
server:
port: 8000
spring:
security:
user:
password: weak
Spring profiles designated by using the spring.profiles
element may optionally be
negated by using the !
character. If both negated and non-negated profiles are
specified for a single document, at least one non-negated profile must match, and no
negated profiles may match.
YAML Shortcomings
YAML files cannot be loaded by using the @PropertySource
annotation. So, in the case
that you need to load values that way, you need to use a properties file.
Using the multi YAML document syntax in profile-specific YAML files can lead to unexpected
behavior. For example, consider the following config in a file called application-dev.yml
,
with the dev
profile being active:
server:
port: 8000
---
spring:
profiles: !test
security:
user:
password: weak
In the example above, profile negation and profile expressions will not behave as expected. We recommend that you don’t combine profile-specific YAML files and multiple YAML documents and stick to using only one of them.
4.2.8. Type-safe Configuration Properties
Using the @Value("${property}")
annotation to inject configuration properties can
sometimes be cumbersome, especially if you are working with multiple properties or your
data is hierarchical in nature. Spring Boot provides an alternative method of working
with properties that lets strongly typed beans govern and validate the configuration of
your application.
JavaBean properties binding
It is possible to bind a bean declaring standard JavaBean properties as shown in the following example:
package com.example;
import java.net.InetAddress;
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import org.springframework.boot.context.properties.ConfigurationProperties;
@ConfigurationProperties("acme")
public class AcmeProperties {
private boolean enabled;
private InetAddress remoteAddress;
private final Security security = new Security();
public boolean isEnabled() { ... }
public void setEnabled(boolean enabled) { ... }
public InetAddress getRemoteAddress() { ... }
public void setRemoteAddress(InetAddress remoteAddress) { ... }
public Security getSecurity() { ... }
public static class Security {
private String username;
private String password;
private List<String> roles = new ArrayList<>(Collections.singleton("USER"));
public String getUsername() { ... }
public void setUsername(String username) { ... }
public String getPassword() { ... }
public void setPassword(String password) { ... }
public List<String> getRoles() { ... }
public void setRoles(List<String> roles) { ... }
}
}
The preceding POJO defines the following properties:
-
acme.enabled
, with a value offalse
by default. -
acme.remote-address
, with a type that can be coerced fromString
. -
acme.security.username
, with a nested "security" object whose name is determined by the name of the property. In particular, the return type is not used at all there and could have beenSecurityProperties
. -
acme.security.password
. -
acme.security.roles
, with a collection ofString
that defaults toUSER
.
Such arrangement relies on a default empty constructor and getters and setters are usually mandatory, since binding is through standard Java Beans property descriptors, just like in Spring MVC. A setter may be omitted in the following cases:
Some people use Project Lombok to add getters and setters automatically. Make sure that Lombok does not generate any particular constructor for such a type, as it is used automatically by the container to instantiate the object. Finally, only standard Java Bean properties are considered and binding on static properties is not supported. |
Constructor binding
The example in the previous section can be rewritten in an immutable fashion as shown in the following example:
package com.example;
import java.net.InetAddress;
import java.util.List;
import org.springframework.boot.context.properties.ConfigurationProperties;
import org.springframework.boot.context.properties.DefaultValue;
@ConfigurationProperties("acme")
public class AcmeProperties {
private final boolean enabled;
private final InetAddress remoteAddress;
private final Security security;
public AcmeProperties(boolean enabled, InetAddress remoteAddress, Security security) {
this.enabled = enabled;
this.remoteAddress = remoteAddress;
this.security = security;
}
public boolean isEnabled() { ... }
public InetAddress getRemoteAddress() { ... }
public Security getSecurity() { ... }
public static class Security {
private final String username;
private final String password;
private final List<String> roles;
public Security(String username, String password,
@DefaultValue("USER") List<String> roles) {
this.username = username;
this.password = password;
this.roles = roles;
}
public String getUsername() { ... }
public String getPassword() { ... }
public List<String> getRoles() { ... }
}
}
In this setup one, and only one constructor must be defined with the list of properties that you wish to bind and not other properties than the ones in the constructor are bound.
Default values can be specified using @DefaultValue
and the same conversion service will
be applied to coerce the String
value to the target type of a missing property.
Enabling @ConfigurationProperties
-annotated types
Spring Boot provides an infrastructure to bind such types and register them as beans
automatically. If your application uses @SpringBootApplication
, classes annotated with
@ConfigurationProperties
will automatically be scanned and registered as beans. By default,
scanning will occur from the package of the class that declares this annotation. If you want
to define specific packages to scan, you can do so using an explicit @ConfigurationPropertiesScan
directive on your @SpringBootApplication
-annotated class as shown in the following example:
@SpringBootApplication
@ConfigurationPropertiesScan({ "com.example.app", "org.acme.another" })
public class MyApplication {
}
Sometimes, classes annotated with @ConfigurationProperties
might not be suitable
for scanning, for example, if you’re developing your own auto-configuration. In these
cases, you can specify the list of types to process on any @Configuration
class as
shown in the following example:
@Configuration(proxyBeanMethods = false)
@EnableConfigurationProperties(AcmeProperties.class)
public class MyConfiguration {
}
When the The bean name in the example above is |
We recommend that @ConfigurationProperties
only deal with the environment and, in
particular, does not inject other beans from the context. In particular, it is not
possible to inject other beans using the constructor as this would trigger the constructor
binder that only deals with the environment.
For corner cases, setter injection can be used or any of the *Aware
interfaces provided
by the framework (such as EnvironmentAware
if you need access to the Environment
).
Annotating a @ConfigurationProperties type with @Component will result in two
beans of the same type if the type is also scanned as part of classpath scanning. If you want
to register the bean yourself using @Component , consider disabling scanning of
@ConfigurationProperties .
|
Using @ConfigurationProperties
-annotated types
This style of configuration works particularly well with the SpringApplication
external
YAML configuration, as shown in the following example:
# application.yml
acme:
remote-address: 192.168.1.1
security:
username: admin
roles:
- USER
- ADMIN
# additional configuration as required
To work with @ConfigurationProperties
beans, you can inject them in the same way
as any other bean, as shown in the following example:
@Service
public class MyService {
private final AcmeProperties properties;
@Autowired
public MyService(AcmeProperties properties) {
this.properties = properties;
}
//...
@PostConstruct
public void openConnection() {
Server server = new Server(this.properties.getRemoteAddress());
// ...
}
}
Using @ConfigurationProperties also lets you generate metadata files that can be
used by IDEs to offer auto-completion for your own keys. See the
appendix for details.
|
Third-party Configuration
As well as using @ConfigurationProperties
to annotate a class, you can also use it on
public @Bean
methods. Doing so can be particularly useful when you want to bind
properties to third-party components that are outside of your control.
To configure a bean from the Environment
properties, add @ConfigurationProperties
to
its bean registration, as shown in the following example:
@ConfigurationProperties(prefix = "another")
@Bean
public AnotherComponent anotherComponent() {
...
}
Any JavaBean property defined with the another
prefix is mapped onto that
AnotherComponent
bean in manner similar to the preceding AcmeProperties
example.
Relaxed Binding
Spring Boot uses some relaxed rules for binding Environment
properties to
@ConfigurationProperties
beans, so there does not need to be an exact match between the
Environment
property name and the bean property name. Common examples where this is
useful include dash-separated environment properties (for example, context-path
binds
to contextPath
), and capitalized environment properties (for example, PORT
binds to
port
).
For example, consider the following @ConfigurationProperties
class:
@ConfigurationProperties(prefix="acme.my-project.person")
public class OwnerProperties {
private String firstName;
public String getFirstName() {
return this.firstName;
}
public void setFirstName(String firstName) {
this.firstName = firstName;
}
}
In the preceding example, the following properties names can all be used:
Property | Note |
---|---|
|
Kebab case, which is recommended for use in |
|
Standard camel case syntax. |
|
Underscore notation, which is an alternative format for use in |
|
Upper case format, which is recommended when using system environment variables. |
The prefix value for the annotation must be in kebab case (lowercase and
separated by - , such as acme.my-project.person ).
|
Property Source | Simple | List |
---|---|---|
Properties Files |
Camel case, kebab case, or underscore notation |
Standard list syntax using |
YAML Files |
Camel case, kebab case, or underscore notation |
Standard YAML list syntax or comma-separated values |
Environment Variables |
Upper case format with underscore as the delimiter. |
Numeric values surrounded by underscores, such as |
System properties |
Camel case, kebab case, or underscore notation |
Standard list syntax using |
We recommend that, when possible, properties are stored in lower-case kebab format,
such as my.property-name=acme .
|
When binding to Map
properties, if the key
contains anything other than lowercase
alpha-numeric characters or -
, you need to use the bracket notation so that the original
value is preserved. If the key is not surrounded by []
, any characters that are not alpha-numeric
or -
are removed. For example, consider binding the following properties to a Map
:
acme:
map:
"[/key1]": value1
"[/key2]": value2
/key3: value3
The properties above will bind to a Map
with /key1
, /key2
and key3
as the keys in the map.
Merging Complex Types
When lists are configured in more than one place, overriding works by replacing the entire list.
For example, assume a MyPojo
object with name
and description
attributes that are
null
by default. The following example exposes a list of MyPojo
objects from
AcmeProperties
:
@ConfigurationProperties("acme")
public class AcmeProperties {
private final List<MyPojo> list = new ArrayList<>();
public List<MyPojo> getList() {
return this.list;
}
}
Consider the following configuration:
acme:
list:
- name: my name
description: my description
---
spring:
profiles: dev
acme:
list:
- name: my another name
If the dev
profile is not active, AcmeProperties.list
contains one MyPojo
entry,
as previously defined. If the dev
profile is enabled, however, the list
still
contains only one entry (with a name of my another name
and a description of null
).
This configuration does not add a second MyPojo
instance to the list, and it does not
merge the items.
When a List
is specified in multiple profiles, the one with the highest priority
(and only that one) is used. Consider the following example:
acme:
list:
- name: my name
description: my description
- name: another name
description: another description
---
spring:
profiles: dev
acme:
list:
- name: my another name
In the preceding example, if the dev
profile is active, AcmeProperties.list
contains
one MyPojo
entry (with a name of my another name
and a description of null
).
For YAML, both comma-separated lists and YAML lists can be used for
completely overriding the contents of the list.
For Map
properties, you can bind with property values drawn from multiple sources. However,
for the same property in multiple sources, the one with the highest priority is used.
The following example exposes a Map<String, MyPojo>
from AcmeProperties
:
@ConfigurationProperties("acme")
public class AcmeProperties {
private final Map<String, MyPojo> map = new HashMap<>();
public Map<String, MyPojo> getMap() {
return this.map;
}
}
Consider the following configuration:
acme:
map:
key1:
name: my name 1
description: my description 1
---
spring:
profiles: dev
acme:
map:
key1:
name: dev name 1
key2:
name: dev name 2
description: dev description 2
If the dev
profile is not active, AcmeProperties.map
contains one entry with key key1
(with a name of my name 1
and a description of my description 1
).
If the dev
profile is enabled, however, map
contains two entries with keys key1
(with a name of dev name 1
and a description of my description 1
) and
key2
(with a name of dev name 2
and a description of dev description 2
).
The preceding merging rules apply to properties from all property sources and not just YAML files. |
Properties Conversion
Spring Boot attempts to coerce the external application properties to the right type when
it binds to the @ConfigurationProperties
beans. If you need custom type conversion, you
can provide a ConversionService
bean (with a bean named conversionService
) or custom
property editors (through a CustomEditorConfigurer
bean) or custom Converters
(with
bean definitions annotated as @ConfigurationPropertiesBinding
).
As this bean is requested very early during the application lifecycle, make sure to
limit the dependencies that your ConversionService is using. Typically, any dependency
that you require may not be fully initialized at creation time. You may want to rename
your custom ConversionService if it is not required for configuration keys coercion and
only rely on custom converters qualified with @ConfigurationPropertiesBinding .
|
Converting durations
Spring Boot has dedicated support for expressing durations. If you expose a
java.time.Duration
property, the following formats in application properties are
available:
-
A regular
long
representation (using milliseconds as the default unit unless a@DurationUnit
has been specified) -
The standard ISO-8601 format used by
java.time.Duration
-
A more readable format where the value and the unit are coupled (e.g.
10s
means 10 seconds)
Consider the following example:
@ConfigurationProperties("app.system")
public class AppSystemProperties {
@DurationUnit(ChronoUnit.SECONDS)
private Duration sessionTimeout = Duration.ofSeconds(30);
private Duration readTimeout = Duration.ofMillis(1000);
public Duration getSessionTimeout() {
return this.sessionTimeout;
}
public void setSessionTimeout(Duration sessionTimeout) {
this.sessionTimeout = sessionTimeout;
}
public Duration getReadTimeout() {
return this.readTimeout;
}
public void setReadTimeout(Duration readTimeout) {
this.readTimeout = readTimeout;
}
}
To specify a session timeout of 30 seconds, 30
, PT30S
and 30s
are all equivalent. A
read timeout of 500ms can be specified in any of the following form: 500
, PT0.5S
and
500ms
.
You can also use any of the supported units. These are:
-
ns
for nanoseconds -
us
for microseconds -
ms
for milliseconds -
s
for seconds -
m
for minutes -
h
for hours -
d
for days
The default unit is milliseconds and can be overridden using @DurationUnit
as illustrated
in the sample above.
If you are upgrading from a previous version that is simply using Long to express
the duration, make sure to define the unit (using @DurationUnit ) if it isn’t
milliseconds alongside the switch to Duration . Doing so gives a transparent upgrade path
while supporting a much richer format.
|
Converting Data Sizes
Spring Framework has a DataSize
value type that allows to express size in bytes. If you
expose a DataSize
property, the following formats in application properties are
available:
-
A regular
long
representation (using bytes as the default unit unless a@DataSizeUnit
has been specified) -
A more readable format where the value and the unit are coupled (e.g.
10MB
means 10 megabytes)
Consider the following example:
@ConfigurationProperties("app.io")
public class AppIoProperties {
@DataSizeUnit(DataUnit.MEGABYTES)
private DataSize bufferSize = DataSize.ofMegabytes(2);
private DataSize sizeThreshold = DataSize.ofBytes(512);
public DataSize getBufferSize() {
return this.bufferSize;
}
public void setBufferSize(DataSize bufferSize) {
this.bufferSize = bufferSize;
}
public DataSize getSizeThreshold() {
return this.sizeThreshold;
}
public void setSizeThreshold(DataSize sizeThreshold) {
this.sizeThreshold = sizeThreshold;
}
}
To specify a buffer size of 10 megabytes, 10
and 10MB
are equivalent. A size threshold
of 256 bytes can be specified as 256
or 256B
.
You can also use any of the supported units. These are:
-
B
for bytes -
KB
for kilobytes -
MB
for megabytes -
GB
for gigabytes -
TB
for terabytes
The default unit is bytes and can be overridden using @DataSizeUnit
as illustrated
in the sample above.
If you are upgrading from a previous version that is simply using Long to express
the size, make sure to define the unit (using @DataSizeUnit ) if it isn’t bytes alongside
the switch to DataSize . Doing so gives a transparent upgrade path while supporting a
much richer format.
|
@ConfigurationProperties Validation
Spring Boot attempts to validate @ConfigurationProperties
classes whenever they are
annotated with Spring’s @Validated
annotation. You can use JSR-303 javax.validation
constraint annotations directly on your configuration class. To do so, ensure that a
compliant JSR-303 implementation is on your classpath and then add constraint annotations
to your fields, as shown in the following example:
@ConfigurationProperties(prefix="acme")
@Validated
public class AcmeProperties {
@NotNull
private InetAddress remoteAddress;
// ... getters and setters
}
You can also trigger validation by annotating the @Bean method that creates the
configuration properties with @Validated .
|
Although nested properties will also be validated when bound, it’s good practice to
also annotate the associated field as @Valid
. This ensure that validation is triggered
even if no nested properties are found. The following example builds on the preceding
AcmeProperties
example:
@ConfigurationProperties(prefix="acme")
@Validated
public class AcmeProperties {
@NotNull
private InetAddress remoteAddress;
@Valid
private final Security security = new Security();
// ... getters and setters
public static class Security {
@NotEmpty
public String username;
// ... getters and setters
}
}
You can also add a custom Spring Validator
by creating a bean definition called
configurationPropertiesValidator
. The @Bean
method should be declared static
. The
configuration properties validator is created very early in the application’s lifecycle,
and declaring the @Bean
method as static lets the bean be created without having to
instantiate the @Configuration
class. Doing so avoids any problems that may be caused
by early instantiation.
The spring-boot-actuator module includes an endpoint that exposes all
@ConfigurationProperties beans. Point your web browser to
/actuator/configprops or use the equivalent JMX endpoint. See the
"Production ready features"
section for details.
|
@ConfigurationProperties vs. @Value
The @Value
annotation is a core container feature, and it does not provide the same
features as type-safe configuration properties. The following table summarizes the
features that are supported by @ConfigurationProperties
and @Value
:
Feature | @ConfigurationProperties |
@Value |
---|---|---|
Yes |
No |
|
Yes |
No |
|
|
No |
Yes |
If you define a set of configuration keys for your own components, we recommend you
group them in a POJO annotated with @ConfigurationProperties
. You should also be aware
that, since @Value
does not support relaxed binding, it is not a good candidate if you
need to provide the value by using environment variables.
Finally, while you can write a SpEL
expression in @Value
, such expressions are not
processed from application
property files.
4.3. Profiles
Spring Profiles provide a way to segregate parts of your application configuration and
make it be available only in certain environments. Any @Component
, @Configuration
or @ConfigurationProperties
can be marked with @Profile
to limit when it is loaded,
as shown in the following example:
@Configuration(proxyBeanMethods = false)
@Profile("production")
public class ProductionConfiguration {
// ...
}
If @ConfigurationProperties beans are registered via @EnableConfigurationProperties
instead of automatic scanning, the @Profile annotation needs to be specified on the @Configuration
class that has the @EnableConfigurationProperties annotation. In the case where @ConfigurationProperties
are scanned, @Profile can be specified on the @ConfigurationProperties class itself.
|
You can use a spring.profiles.active
Environment
property to specify which profiles
are active. You can specify the property in any of the ways described earlier in this
chapter. For example, you could include it in your application.properties
, as shown in
the following example:
spring.profiles.active=dev,hsqldb
You could also specify it on the command line by using the following switch:
--spring.profiles.active=dev,hsqldb
.
4.3.1. Adding Active Profiles
The spring.profiles.active
property follows the same ordering rules as other
properties: The highest PropertySource
wins. This means that you can specify active
profiles in application.properties
and then replace them by using the command line
switch.
Sometimes, it is useful to have profile-specific properties that add to the active
profiles rather than replace them. The spring.profiles.include
property can be used to
unconditionally add active profiles. The SpringApplication
entry point also has a Java
API for setting additional profiles (that is, on top of those activated by the
spring.profiles.active
property). See the setAdditionalProfiles()
method in
SpringApplication.
For example, when an application with the following properties is run by using the
switch, --spring.profiles.active=prod
, the proddb
and prodmq
profiles are also
activated:
---
my.property: fromyamlfile
---
spring.profiles: prod
spring.profiles.include:
- proddb
- prodmq
Remember that the spring.profiles property can be defined in a YAML document to
determine when this particular document is included in the configuration. See
Change Configuration Depending on the Environment for more details.
|
4.3.2. Programmatically Setting Profiles
You can programmatically set active profiles by calling
SpringApplication.setAdditionalProfiles(…)
before your application runs. It is also
possible to activate profiles by using Spring’s ConfigurableEnvironment
interface.
4.3.3. Profile-specific Configuration Files
Profile-specific variants of both application.properties
(or application.yml
) and
files referenced through @ConfigurationProperties
are considered as files and loaded.
See "Profile-specific Properties" for details.
4.4. Logging
Spring Boot uses Commons Logging for all internal logging but leaves the underlying log implementation open. Default configurations are provided for Java Util Logging, Log4J2, and Logback. In each case, loggers are pre-configured to use console output with optional file output also available.
By default, if you use the “Starters”, Logback is used for logging. Appropriate Logback routing is also included to ensure that dependent libraries that use Java Util Logging, Commons Logging, Log4J, or SLF4J all work correctly.
There are a lot of logging frameworks available for Java. Do not worry if the above list seems confusing. Generally, you do not need to change your logging dependencies and the Spring Boot defaults work just fine. |
4.4.1. Log Format
The default log output from Spring Boot resembles the following example:
2014-03-05 10:57:51.112 INFO 45469 --- [ main] org.apache.catalina.core.StandardEngine : Starting Servlet Engine: Apache Tomcat/7.0.52 2014-03-05 10:57:51.253 INFO 45469 --- [ost-startStop-1] o.a.c.c.C.[Tomcat].[localhost].[/] : Initializing Spring embedded WebApplicationContext 2014-03-05 10:57:51.253 INFO 45469 --- [ost-startStop-1] o.s.web.context.ContextLoader : Root WebApplicationContext: initialization completed in 1358 ms 2014-03-05 10:57:51.698 INFO 45469 --- [ost-startStop-1] o.s.b.c.e.ServletRegistrationBean : Mapping servlet: 'dispatcherServlet' to [/] 2014-03-05 10:57:51.702 INFO 45469 --- [ost-startStop-1] o.s.b.c.embedded.FilterRegistrationBean : Mapping filter: 'hiddenHttpMethodFilter' to: [/*]
The following items are output:
-
Date and Time: Millisecond precision and easily sortable.
-
Log Level:
ERROR
,WARN
,INFO
,DEBUG
, orTRACE
. -
Process ID.
-
A
---
separator to distinguish the start of actual log messages. -
Thread name: Enclosed in square brackets (may be truncated for console output).
-
Logger name: This is usually the source class name (often abbreviated).
-
The log message.
Logback does not have a FATAL level. It is mapped to ERROR .
|
4.4.2. Console Output
The default log configuration echoes messages to the console as they are written. By
default, ERROR
-level, WARN
-level, and INFO
-level messages are logged. You can also
enable a “debug” mode by starting your application with a --debug
flag.
$ java -jar myapp.jar --debug
You can also specify debug=true in your application.properties .
|
When the debug mode is enabled, a selection of core loggers (embedded container,
Hibernate, and Spring Boot) are configured to output more information. Enabling the debug
mode does not configure your application to log all messages with DEBUG
level.
Alternatively, you can enable a “trace” mode by starting your application with a
--trace
flag (or trace=true
in your application.properties
). Doing so enables trace
logging for a selection of core loggers (embedded container, Hibernate schema generation,
and the whole Spring portfolio).
Color-coded Output
If your terminal supports ANSI, color output is used to aid readability. You can set
spring.output.ansi.enabled
to a
supported value to override the auto
detection.
Color coding is configured by using the %clr
conversion word. In its simplest form, the
converter colors the output according to the log level, as shown in the following
example:
%clr(%5p)
The following table describes the mapping of log levels to colors:
Level | Color |
---|---|
|
Red |
|
Red |
|
Yellow |
|
Green |
|
Green |
|
Green |
Alternatively, you can specify the color or style that should be used by providing it as an option to the conversion. For example, to make the text yellow, use the following setting:
%clr(%d{yyyy-MM-dd HH:mm:ss.SSS}){yellow}
The following colors and styles are supported:
-
blue
-
cyan
-
faint
-
green
-
magenta
-
red
-
yellow
4.4.3. File Output
By default, Spring Boot logs only to the console and does not write log files. If you
want to write log files in addition to the console output, you need to set a
logging.file.name
or logging.file.path
property (for example, in your
application.properties
).
The following table shows how the logging.*
properties can be used together:
logging.file.name |
logging.file.path |
Example | Description |
---|---|---|---|
(none) |
(none) |
Console only logging. |
|
Specific file |
(none) |
|
Writes to the specified log file. Names can be an exact location or relative to the current directory. |
(none) |
Specific directory |
|
Writes |
Log files rotate when they reach 10 MB and, as with console output, ERROR
-level,
WARN
-level, and INFO
-level messages are logged by default. Size limits can be changed
using the logging.file.max-size
property. Previously rotated files are archived
indefinitely unless the logging.file.max-history
property has been set. The total size
of log archives can be capped using logging.file.total-size-cap
. When the total size of
log archives exceeds that threshold, backups will be deleted. To force log archive cleanup
on application startup, use the logging.file.clean-history-on-start
property.
The logging system is initialized early in the application lifecycle. Consequently,
logging properties are not found in property files loaded through @PropertySource
annotations.
|
Logging properties are independent of the actual logging infrastructure. As a
result, specific configuration keys (such as logback.configurationFile for Logback) are
not managed by spring Boot.
|
4.4.4. Log Levels
All the supported logging systems can have the logger levels set in the Spring
Environment
(for example, in application.properties
) by using
logging.level.<logger-name>=<level>
where level
is one of TRACE, DEBUG, INFO, WARN,
ERROR, FATAL, or OFF. The root
logger can be configured by using logging.level.root
.
The following example shows potential logging settings in application.properties
:
logging.level.root=WARN
logging.level.org.springframework.web=DEBUG
logging.level.org.hibernate=ERROR
4.4.5. Log Groups
It’s often useful to be able to group related loggers together so that they can all be configured at the same time. For example, you might commonly change the logging levels for all Tomcat related loggers, but you can’t easily remember top level packages.
To help with this, Spring Boot allows you to define logging groups in your Spring
Environment
. For example, here’s how you could define a “tomcat” group by adding
it to your application.properties
:
logging.group.tomcat=org.apache.catalina, org.apache.coyote, org.apache.tomcat
Once defined, you can change the level for all the loggers in the group with a single line:
logging.level.tomcat=TRACE
Spring Boot includes the following pre-defined logging groups that can be used out-of-the-box:
Name | Loggers |
---|---|
web |
|
sql |
|
4.4.6. Custom Log Configuration
The various logging systems can be activated by including the appropriate libraries on
the classpath and can be further customized by providing a suitable configuration file in
the root of the classpath or in a location specified by the following Spring Environment
property: logging.config
.
You can force Spring Boot to use a particular logging system by using the
org.springframework.boot.logging.LoggingSystem
system property. The value should be the
fully qualified class name of a LoggingSystem
implementation. You can also disable
Spring Boot’s logging configuration entirely by using a value of none
.
Since logging is initialized before the ApplicationContext is created, it is
not possible to control logging from @PropertySources in Spring @Configuration files.
The only way to change the logging system or disable it entirely is via System properties.
|
Depending on your logging system, the following files are loaded:
Logging System | Customization |
---|---|
Logback |
|
Log4j2 |
|
JDK (Java Util Logging) |
|
When possible, we recommend that you use the -spring variants for your logging
configuration (for example, logback-spring.xml rather than logback.xml ). If you use
standard configuration locations, Spring cannot completely control log initialization.
|
There are known classloading issues with Java Util Logging that cause problems when running from an 'executable jar'. We recommend that you avoid it when running from an 'executable jar' if at all possible. |
To help with the customization, some other properties are transferred from the Spring
Environment
to System properties, as described in the following table:
Spring Environment | System Property | Comments |
---|---|---|
|
|
The conversion word used when logging exceptions. |
|
|
Whether to clean the archive log files on startup (if LOG_FILE enabled). (Only supported with the default Logback setup.) |
|
|
If defined, it is used in the default log configuration. |
|
|
Maximum log file size (if LOG_FILE enabled). (Only supported with the default Logback setup.) |
|
|
Maximum number of archive log files to keep (if LOG_FILE enabled). (Only supported with the default Logback setup.) |
|
|
If defined, it is used in the default log configuration. |
|
|
Total size of log backups to be kept (if LOG_FILE enabled). (Only supported with the default Logback setup.) |
|
|
The log pattern to use on the console (stdout). (Only supported with the default Logback setup.) |
|
|
Appender pattern for log date format. (Only supported with the default Logback setup.) |
|
|
The log pattern to use in a file (if |
|
|
The format to use when rendering the log level (default |
|
|
The current process ID (discovered if possible and when not already defined as an OS environment variable). |
All the supported logging systems can consult System properties when parsing their
configuration files. See the default configurations in spring-boot.jar
for examples:
If you want to use a placeholder in a logging property, you should use
Spring Boot’s syntax and not
the syntax of the underlying framework. Notably, if you use Logback, you should use |
You can add MDC and other ad-hoc content to log lines by overriding only the
2015-09-30 12:30:04.031 user:someone INFO 22174 --- [ nio-8080-exec-0] demo.Controller Handling authenticated request |
4.4.7. Logback Extensions
Spring Boot includes a number of extensions to Logback that can help with advanced
configuration. You can use these extensions in your logback-spring.xml
configuration
file.
Because the standard logback.xml configuration file is loaded too early, you
cannot use extensions in it. You need to either use logback-spring.xml or define a
logging.config property.
|
The extensions cannot be used with Logback’s configuration scanning. If you attempt to do so, making changes to the configuration file results in an error similar to one of the following being logged: |
ERROR in ch.qos.logback.core.joran.spi.Interpreter@4:71 - no applicable action for [springProperty], current ElementPath is [[configuration][springProperty]] ERROR in ch.qos.logback.core.joran.spi.Interpreter@4:71 - no applicable action for [springProfile], current ElementPath is [[configuration][springProfile]]
Profile-specific Configuration
The <springProfile>
tag lets you optionally include or exclude sections of
configuration based on the active Spring profiles. Profile sections are supported
anywhere within the <configuration>
element. Use the name
attribute to specify which
profile accepts the configuration. The <springProfile>
tag can contain a simple profile
name (for example staging
) or a profile expression. A profile expression allows for more
complicated profile logic to be expressed, for example
production & (eu-central | eu-west)
. Check the
reference guide for more
details. The following listing shows three sample profiles:
<springProfile name="staging">
<!-- configuration to be enabled when the "staging" profile is active -->
</springProfile>
<springProfile name="dev | staging">
<!-- configuration to be enabled when the "dev" or "staging" profiles are active -->
</springProfile>
<springProfile name="!production">
<!-- configuration to be enabled when the "production" profile is not active -->
</springProfile>
Environment Properties
The <springProperty>
tag lets you expose properties from the Spring Environment
for
use within Logback. Doing so can be useful if you want to access values from your
application.properties
file in your Logback configuration. The tag works in a similar
way to Logback’s standard <property>
tag. However, rather than specifying a direct
value
, you specify the source
of the property (from the Environment
). If you need
to store the property somewhere other than in local
scope, you can use the scope
attribute. If you need a fallback value (in case the property is not set in the
Environment
), you can use the defaultValue
attribute. The following example shows how
to expose properties for use within Logback:
<springProperty scope="context" name="fluentHost" source="myapp.fluentd.host"
defaultValue="localhost"/>
<appender name="FLUENT" class="ch.qos.logback.more.appenders.DataFluentAppender">
<remoteHost>${fluentHost}</remoteHost>
...
</appender>
The source must be specified in kebab case (such as my.property-name ).
However, properties can be added to the Environment by using the relaxed rules.
|
4.5. Internationalization
Spring Boot supports localized messages so that your application can cater to users
of different language preferences. By default, Spring Boot looks for the presence of
a messages
resource bundle at the root of the classpath.
The auto-configuration applies when the default properties file for the configured
resource bundle is available (i.e. messages.properties by default). If your resource
bundle contains only language-specific properties files, you are required to add the
default. If no properties file is found that matches any of the configured base names,
there will be no auto-configured MessageSource .
|
The basename of the resource bundle as well as several other attributes can be configured
using the spring.messages
namespace, as shown in the following example:
spring.messages.basename=messages,config.i18n.messages
spring.messages.fallback-to-system-locale=false
spring.messages.basename supports comma-separated list of locations, either a
package qualifier or a resource resolved from the classpath root.
|
See
MessageSourceProperties
for more supported options.
4.6. JSON
Spring Boot provides integration with three JSON mapping libraries:
-
Gson
-
Jackson
-
JSON-B
Jackson is the preferred and default library.
4.6.1. Jackson
Auto-configuration for Jackson is provided and Jackson is part of
spring-boot-starter-json
. When Jackson is on the classpath an ObjectMapper
bean is automatically configured. Several configuration properties are provided for
customizing the configuration of the
ObjectMapper
.
4.7. Developing Web Applications
Spring Boot is well suited for web application development. You can create a
self-contained HTTP server by using embedded Tomcat, Jetty, Undertow, or Netty. Most web
applications use the spring-boot-starter-web
module to get up and running quickly. You
can also choose to build reactive web applications by using the
spring-boot-starter-webflux
module.
If you have not yet developed a Spring Boot web application, you can follow the "Hello World!" example in the Getting started section.
4.7.1. The “Spring Web MVC Framework”
The Spring Web MVC framework (often referred to as simply
“Spring MVC”) is a rich “model view controller” web framework. Spring MVC lets you
create special @Controller
or @RestController
beans to handle incoming HTTP requests.
Methods in your controller are mapped to HTTP by using @RequestMapping
annotations.
The following code shows a typical @RestController
that serves JSON data:
@RestController
@RequestMapping(value="/users")
public class MyRestController {
@RequestMapping(value="/\{user}", method=RequestMethod.GET)
public User getUser(@PathVariable Long user) {
// ...
}
@RequestMapping(value="/\{user}/customers", method=RequestMethod.GET)
List<Customer> getUserCustomers(@PathVariable Long user) {
// ...
}
@RequestMapping(value="/\{user}", method=RequestMethod.DELETE)
public User deleteUser(@PathVariable Long user) {
// ...
}
}
Spring MVC is part of the core Spring Framework, and detailed information is available in the reference documentation. There are also several guides that cover Spring MVC available at spring.io/guides.
Spring MVC Auto-configuration
Spring Boot provides auto-configuration for Spring MVC that works well with most applications.
The auto-configuration adds the following features on top of Spring’s defaults:
-
Inclusion of
ContentNegotiatingViewResolver
andBeanNameViewResolver
beans. -
Support for serving static resources, including support for WebJars (covered later in this document)).
-
Automatic registration of
Converter
,GenericConverter
, andFormatter
beans. -
Support for
HttpMessageConverters
(covered later in this document). -
Automatic registration of
MessageCodesResolver
(covered later in this document). -
Static
index.html
support. -
Custom
Favicon
support (covered later in this document). -
Automatic use of a
ConfigurableWebBindingInitializer
bean (covered later in this document).
If you want to keep Spring Boot MVC features and you want to add additional
MVC configuration (interceptors, formatters, view
controllers, and other features), you can add your own @Configuration
class of type
WebMvcConfigurer
but without @EnableWebMvc
. If you wish to provide custom
instances of RequestMappingHandlerMapping
, RequestMappingHandlerAdapter
, or
ExceptionHandlerExceptionResolver
, you can declare a WebMvcRegistrationsAdapter
instance to provide such components.
If you want to take complete control of Spring MVC, you can add your own @Configuration
annotated with @EnableWebMvc
.
HttpMessageConverters
Spring MVC uses the HttpMessageConverter
interface to convert HTTP requests and
responses. Sensible defaults are included out of the box. For example, objects can be
automatically converted to JSON (by using the Jackson library) or XML (by using the
Jackson XML extension, if available, or by using JAXB if the Jackson XML extension is not
available). By default, strings are encoded in UTF-8
.
If you need to add or customize converters, you can use Spring Boot’s
HttpMessageConverters
class, as shown in the following listing:
import org.springframework.boot.autoconfigure.http.HttpMessageConverters;
import org.springframework.context.annotation.*;
import org.springframework.http.converter.*;
@Configuration(proxyBeanMethods = false)
public class MyConfiguration {
@Bean
public HttpMessageConverters customConverters() {
HttpMessageConverter<?> additional = ...
HttpMessageConverter<?> another = ...
return new HttpMessageConverters(additional, another);
}
}
Any HttpMessageConverter
bean that is present in the context is added to the list of
converters. You can also override default converters in the same way.
Custom JSON Serializers and Deserializers
If you use Jackson to serialize and deserialize JSON data, you might want to write your
own JsonSerializer
and JsonDeserializer
classes. Custom serializers are usually
registered with Jackson through
a module, but Spring Boot provides an alternative @JsonComponent
annotation that makes
it easier to directly register Spring Beans.
You can use the @JsonComponent
annotation directly on JsonSerializer
,
JsonDeserializer
or KeyDeserializer
implementations. You can also use it on classes
that contain serializers/deserializers as inner classes, as shown in the following example:
import java.io.*;
import com.fasterxml.jackson.core.*;
import com.fasterxml.jackson.databind.*;
import org.springframework.boot.jackson.*;
@JsonComponent
public class Example {
public static class Serializer extends JsonSerializer<SomeObject> {
// ...
}
public static class Deserializer extends JsonDeserializer<SomeObject> {
// ...
}
}
All @JsonComponent
beans in the ApplicationContext
are automatically registered with
Jackson. Because @JsonComponent
is meta-annotated with @Component
, the usual
component-scanning rules apply.
Spring Boot also provides
JsonObjectSerializer
and
JsonObjectDeserializer
base
classes that provide useful alternatives to the standard Jackson versions when
serializing objects. See
JsonObjectSerializer
and JsonObjectDeserializer
in
the Javadoc for details.
MessageCodesResolver
Spring MVC has a strategy for generating error codes for rendering error messages from
binding errors: MessageCodesResolver
. If you set the
spring.mvc.message-codes-resolver.format
property PREFIX_ERROR_CODE
or
POSTFIX_ERROR_CODE
, Spring Boot creates one for you (see the enumeration in
DefaultMessageCodesResolver.Format
).
Static Content
By default, Spring Boot serves static content from a directory called /static
(or
/public
or /resources
or /META-INF/resources
) in the classpath or from the root of
the ServletContext
. It uses the ResourceHttpRequestHandler
from Spring MVC so that
you can modify that behavior by adding your own WebMvcConfigurer
and overriding the
addResourceHandlers
method.
In a stand-alone web application, the default servlet from the container is also enabled
and acts as a fallback, serving content from the root of the ServletContext
if Spring
decides not to handle it. Most of the time, this does not happen (unless you modify the
default MVC configuration), because Spring can always handle requests through the
DispatcherServlet
.
By default, resources are mapped on /**
, but you can tune that with the
spring.mvc.static-path-pattern
property. For instance, relocating all resources to
/resources/**
can be achieved as follows:
spring.mvc.static-path-pattern=/resources/**
You can also customize the static resource locations by using the
spring.resources.static-locations
property (replacing the default values with a list of
directory locations). The root Servlet context path, "/"
, is automatically added as a
location as well.
In addition to the “standard” static resource locations mentioned earlier, a special
case is made for Webjars content. Any resources with a path in
/webjars/**
are served from jar files if they are packaged in the Webjars format.
Do not use the src/main/webapp directory if your application is packaged as a jar.
Although this directory is a common standard, it works only with war packaging, and it
is silently ignored by most build tools if you generate a jar.
|
Spring Boot also supports the advanced resource handling features provided by Spring MVC, allowing use cases such as cache-busting static resources or using version agnostic URLs for Webjars.
To use version agnostic URLs for Webjars, add the webjars-locator-core
dependency.
Then declare your Webjar. Using jQuery as an example, adding
"/webjars/jquery/jquery.min.js"
results in
"/webjars/jquery/x.y.z/jquery.min.js"
. where x.y.z
is the Webjar version.
If you use JBoss, you need to declare the webjars-locator-jboss-vfs
dependency instead of the webjars-locator-core . Otherwise, all Webjars resolve as a
404 .
|
To use cache busting, the following configuration configures a cache busting solution for
all static resources, effectively adding a content hash, such as
<link href="/css/spring-2a2d595e6ed9a0b24f027f2b63b134d6.css"/>
, in URLs:
spring.resources.chain.strategy.content.enabled=true
spring.resources.chain.strategy.content.paths=/**
Links to resources are rewritten in templates at runtime, thanks to a
ResourceUrlEncodingFilter that is auto-configured for Thymeleaf and FreeMarker. You
should manually declare this filter when using JSPs. Other template engines are currently
not automatically supported but can be with custom template macros/helpers and the use of
the
ResourceUrlProvider .
|
When loading resources dynamically with, for example, a JavaScript module loader, renaming files is not an option. That is why other strategies are also supported and can be combined. A "fixed" strategy adds a static version string in the URL without changing the file name, as shown in the following example:
spring.resources.chain.strategy.content.enabled=true
spring.resources.chain.strategy.content.paths=/**
spring.resources.chain.strategy.fixed.enabled=true
spring.resources.chain.strategy.fixed.paths=/js/lib/
spring.resources.chain.strategy.fixed.version=v12
With this configuration, JavaScript modules located under "/js/lib/"
use a fixed
versioning strategy ("/v12/js/lib/mymodule.js"
), while other resources still use the
content one (<link href="/css/spring-2a2d595e6ed9a0b24f027f2b63b134d6.css"/>
).
See ResourceProperties
for more supported options.
This feature has been thoroughly described in a dedicated blog post and in Spring Framework’s reference documentation. |
Welcome Page
Spring Boot supports both static and templated welcome pages. It first looks for an
index.html
file in the configured static content locations. If one is not found, it
then looks for an index
template. If either is found, it is automatically used as the
welcome page of the application.
Custom Favicon
Spring Boot looks for a favicon.ico
in the configured static content locations and the
root of the classpath (in that order). If such a file is present, it is automatically
used as the favicon of the application.
Path Matching and Content Negotiation
Spring MVC can map incoming HTTP requests to handlers by looking at the request path and
matching it to the mappings defined in your application (for example, @GetMapping
annotations on Controller methods).
Spring Boot chooses to disable suffix pattern matching by default, which means that
requests like "GET /projects/spring-boot.json"
won’t be matched to
@GetMapping("/projects/spring-boot")
mappings.
This is considered as a
best practice
for Spring MVC applications. This feature was mainly useful in the past for HTTP
clients which did not send proper "Accept" request headers; we needed to make sure
to send the correct Content Type to the client. Nowadays, Content Negotiation
is much more reliable.
There are other ways to deal with HTTP clients that don’t consistently send proper
"Accept" request headers. Instead of using suffix matching, we can use a query
parameter to ensure that requests like "GET /projects/spring-boot?format=json"
will be mapped to @GetMapping("/projects/spring-boot")
:
spring.mvc.contentnegotiation.favor-parameter=true
# We can change the parameter name, which is "format" by default:
# spring.mvc.contentnegotiation.parameter-name=myparam
# We can also register additional file extensions/media types with:
spring.mvc.contentnegotiation.media-types.markdown=text/markdown
If you understand the caveats and would still like your application to use suffix pattern matching, the following configuration is required:
spring.mvc.contentnegotiation.favor-path-extension=true
spring.mvc.pathmatch.use-suffix-pattern=true
Alternatively, rather than open all suffix patterns, it’s more secure to just support registered suffix patterns:
spring.mvc.contentnegotiation.favor-path-extension=true
spring.mvc.pathmatch.use-registered-suffix-pattern=true
# You can also register additional file extensions/media types with:
# spring.mvc.contentnegotiation.media-types.adoc=text/asciidoc
ConfigurableWebBindingInitializer
Spring MVC uses a WebBindingInitializer
to initialize a WebDataBinder
for a
particular request. If you create your own ConfigurableWebBindingInitializer
@Bean
,
Spring Boot automatically configures Spring MVC to use it.
Template Engines
As well as REST web services, you can also use Spring MVC to serve dynamic HTML content. Spring MVC supports a variety of templating technologies, including Thymeleaf, FreeMarker, and JSPs. Also, many other templating engines include their own Spring MVC integrations.
Spring Boot includes auto-configuration support for the following templating engines:
If possible, JSPs should be avoided. There are several known limitations when using them with embedded servlet containers. |
When you use one of these templating engines with the default configuration, your
templates are picked up automatically from src/main/resources/templates
.
Depending on how you run your application, IntelliJ IDEA orders the classpath
differently. Running your application in the IDE from its main method results in a
different ordering than when you run your application by using Maven or Gradle or from
its packaged jar. This can cause Spring Boot to fail to find the templates on the
classpath. If you have this problem, you can reorder the classpath in the IDE to place
the module’s classes and resources first. Alternatively, you can configure the template
prefix to search every templates directory on the classpath, as follows:
classpath*:/templates/ .
|
Error Handling
By default, Spring Boot provides an /error
mapping that handles all errors in a
sensible way, and it is registered as a “global” error page in the servlet container.
For machine clients, it produces a JSON response with details of the error, the HTTP
status, and the exception message. For browser clients, there is a “whitelabel” error
view that renders the same data in HTML format (to customize it, add a View
that
resolves to error
). To replace the default behavior completely, you can implement
ErrorController
and register a bean definition of that type or add a bean of type
ErrorAttributes
to use the existing mechanism but replace the contents.
The BasicErrorController can be used as a base class for a custom
ErrorController . This is particularly useful if you want to add a handler for a new
content type (the default is to handle text/html specifically and provide a fallback
for everything else). To do so, extend BasicErrorController , add a public method with a
@RequestMapping that has a produces attribute, and create a bean of your new type.
|
You can also define a class annotated with @ControllerAdvice
to customize the JSON
document to return for a particular controller and/or exception type, as shown in the
following example:
@ControllerAdvice(basePackageClasses = AcmeController.class)
public class AcmeControllerAdvice extends ResponseEntityExceptionHandler {
@ExceptionHandler(YourException.class)
@ResponseBody
ResponseEntity<?> handleControllerException(HttpServletRequest request, Throwable ex) {
HttpStatus status = getStatus(request);
return new ResponseEntity<>(new CustomErrorType(status.value(), ex.getMessage()), status);
}
private HttpStatus getStatus(HttpServletRequest request) {
Integer statusCode = (Integer) request.getAttribute("javax.servlet.error.status_code");
if (statusCode == null) {
return HttpStatus.INTERNAL_SERVER_ERROR;
}
return HttpStatus.valueOf(statusCode);
}
}
In the preceding example, if YourException
is thrown by a controller defined in the
same package as AcmeController
, a JSON representation of the CustomErrorType
POJO is
used instead of the ErrorAttributes
representation.
Custom Error Pages
If you want to display a custom HTML error page for a given status code, you can add a
file to an /error
folder. Error pages can either be static HTML (that is, added under
any of the static resource folders) or be built by using templates. The name of the file
should be the exact status code or a series mask.
For example, to map 404
to a static HTML file, your folder structure would be as
follows:
src/
+- main/
+- java/
| + <source code>
+- resources/
+- public/
+- error/
| +- 404.html
+- <other public assets>
To map all 5xx
errors by using a FreeMarker template, your folder structure would be as
follows:
src/
+- main/
+- java/
| + <source code>
+- resources/
+- templates/
+- error/
| +- 5xx.ftlh
+- <other templates>
For more complex mappings, you can also add beans that implement the ErrorViewResolver
interface, as shown in the following example:
public class MyErrorViewResolver implements ErrorViewResolver {
@Override
public ModelAndView resolveErrorView(HttpServletRequest request,
HttpStatus status, Map<String, Object> model) {
// Use the request or status to optionally return a ModelAndView
return ...
}
}
You can also use regular Spring MVC features such as
@ExceptionHandler
methods and
@ControllerAdvice
. The
ErrorController
then picks up any unhandled exceptions.
Mapping Error Pages outside of Spring MVC
For applications that do not use Spring MVC, you can use the ErrorPageRegistrar
interface to directly register ErrorPages
. This abstraction works directly with the
underlying embedded servlet container and works even if you do not have a Spring MVC
DispatcherServlet
.
@Bean
public ErrorPageRegistrar errorPageRegistrar(){
return new MyErrorPageRegistrar();
}
// ...
private static class MyErrorPageRegistrar implements ErrorPageRegistrar {
@Override
public void registerErrorPages(ErrorPageRegistry registry) {
registry.addErrorPages(new ErrorPage(HttpStatus.BAD_REQUEST, "/400"));
}
}
If you register an ErrorPage with a path that ends up being handled by a Filter
(as is common with some non-Spring web frameworks, like Jersey and Wicket), then the
Filter has to be explicitly registered as an ERROR dispatcher, as shown in the
following example:
|
@Bean
public FilterRegistrationBean myFilter() {
FilterRegistrationBean registration = new FilterRegistrationBean();
registration.setFilter(new MyFilter());
...
registration.setDispatcherTypes(EnumSet.allOf(DispatcherType.class));
return registration;
}
Note that the default FilterRegistrationBean
does not include the ERROR
dispatcher
type.
CAUTION:When deployed to a servlet container, Spring Boot uses its error page filter to
forward a request with an error status to the appropriate error page. The request can only
be forwarded to the correct error page if the response has not already been committed. By
default, WebSphere Application Server 8.0 and later commits the response upon successful
completion of a servlet’s service method. You should disable this behavior by setting
com.ibm.ws.webcontainer.invokeFlushAfterService
to false
.
Spring HATEOAS
If you develop a RESTful API that makes use of hypermedia, Spring Boot provides
auto-configuration for Spring HATEOAS that works well with most applications. The
auto-configuration replaces the need to use @EnableHypermediaSupport
and registers a
number of beans to ease building hypermedia-based applications, including a
LinkDiscoverers
(for client side support) and an ObjectMapper
configured to correctly
marshal responses into the desired representation. The ObjectMapper
is customized by
setting the various spring.jackson.*
properties or, if one exists, by a
Jackson2ObjectMapperBuilder
bean.
You can take control of Spring HATEOAS’s configuration by using
@EnableHypermediaSupport
. Note that doing so disables the ObjectMapper
customization
described earlier.
CORS Support
Cross-origin resource sharing (CORS) is a W3C specification implemented by most browsers that lets you specify in a flexible way what kind of cross-domain requests are authorized, instead of using some less secure and less powerful approaches such as IFRAME or JSONP.
As of version 4.2, Spring MVC supports CORS.
Using controller method
CORS configuration with
@CrossOrigin
annotations in your Spring Boot application does not require any specific configuration.
Global CORS configuration can be
defined by registering a WebMvcConfigurer
bean with a customized
addCorsMappings(CorsRegistry)
method, as shown in the following example:
@Configuration(proxyBeanMethods = false)
public class MyConfiguration {
@Bean
public WebMvcConfigurer corsConfigurer() {
return new WebMvcConfigurer() {
@Override
public void addCorsMappings(CorsRegistry registry) {
registry.addMapping("/api/**");
}
};
}
}
4.7.2. The “Spring WebFlux Framework”
Spring WebFlux is the new reactive web framework introduced in Spring Framework 5.0. Unlike Spring MVC, it does not require the Servlet API, is fully asynchronous and non-blocking, and implements the Reactive Streams specification through the Reactor project.
Spring WebFlux comes in two flavors: functional and annotation-based. The annotation-based one is quite close to the Spring MVC model, as shown in the following example:
@RestController
@RequestMapping("/users")
public class MyRestController {
@GetMapping("/\{user}")
public Mono<User> getUser(@PathVariable Long user) {
// ...
}
@GetMapping("/\{user}/customers")
public Flux<Customer> getUserCustomers(@PathVariable Long user) {
// ...
}
@DeleteMapping("/\{user}")
public Mono<User> deleteUser(@PathVariable Long user) {
// ...
}
}
“WebFlux.fn”, the functional variant, separates the routing configuration from the actual handling of the requests, as shown in the following example:
@Configuration(proxyBeanMethods = false)
public class RoutingConfiguration {
@Bean
public RouterFunction<ServerResponse> monoRouterFunction(UserHandler userHandler) {
return route(GET("/\{user}").and(accept(APPLICATION_JSON)), userHandler::getUser)
.andRoute(GET("/\{user}/customers").and(accept(APPLICATION_JSON)), userHandler::getUserCustomers)
.andRoute(DELETE("/\{user}").and(accept(APPLICATION_JSON)), userHandler::deleteUser);
}
}
@Component
public class UserHandler {
public Mono<ServerResponse> getUser(ServerRequest request) {
// ...
}
public Mono<ServerResponse> getUserCustomers(ServerRequest request) {
// ...
}
public Mono<ServerResponse> deleteUser(ServerRequest request) {
// ...
}
}
WebFlux is part of the Spring Framework and detailed information is available in its reference documentation.
You can define as many RouterFunction beans as you like to modularize the
definition of the router. Beans can be ordered if you need to apply a precedence.
|
To get started, add the spring-boot-starter-webflux
module to your application.
Adding both spring-boot-starter-web and spring-boot-starter-webflux modules in
your application results in Spring Boot auto-configuring Spring MVC, not WebFlux. This
behavior has been chosen because many Spring developers add spring-boot-starter-webflux
to their Spring MVC application to use the reactive WebClient . You can still enforce
your choice by setting the chosen application type to
SpringApplication.setWebApplicationType(WebApplicationType.REACTIVE) .
|
Spring WebFlux Auto-configuration
Spring Boot provides auto-configuration for Spring WebFlux that works well with most applications.
The auto-configuration adds the following features on top of Spring’s defaults:
-
Configuring codecs for
HttpMessageReader
andHttpMessageWriter
instances (described later in this document). -
Support for serving static resources, including support for WebJars (described later in this document).
If you want to keep Spring Boot WebFlux features and you want to add additional
WebFlux configuration, you can add your own
@Configuration
class of type WebFluxConfigurer
but without @EnableWebFlux
.
If you want to take complete control of Spring WebFlux, you can add your own
@Configuration
annotated with @EnableWebFlux
.
HTTP Codecs with HttpMessageReaders and HttpMessageWriters
Spring WebFlux uses the HttpMessageReader
and HttpMessageWriter
interfaces to convert
HTTP requests and responses. They are configured with CodecConfigurer
to have sensible
defaults by looking at the libraries available in your classpath.
Spring Boot applies further customization by using CodecCustomizer
instances. For
example, spring.jackson.*
configuration keys are applied to the Jackson codec.
If you need to add or customize codecs, you can create a custom CodecCustomizer
component, as shown in the following example:
import org.springframework.boot.web.codec.CodecCustomizer;
@Configuration(proxyBeanMethods = false)
public class MyConfiguration {
@Bean
public CodecCustomizer myCodecCustomizer() {
return codecConfigurer -> {
// ...
}
}
}
You can also leverage Boot’s custom JSON serializers and deserializers.
Static Content
By default, Spring Boot serves static content from a directory called /static
(or
/public
or /resources
or /META-INF/resources
) in the classpath. It uses the
ResourceWebHandler
from Spring WebFlux so that you can modify that behavior by adding
your own WebFluxConfigurer
and overriding the addResourceHandlers
method.
By default, resources are mapped on /**
, but you can tune that by setting the
spring.webflux.static-path-pattern
property. For instance, relocating all resources to
/resources/**
can be achieved as follows:
spring.webflux.static-path-pattern=/resources/**
You can also customize the static resource locations by using
spring.resources.static-locations
. Doing so replaces the default values with a list of
directory locations. If you do so, the default welcome page detection switches to your
custom locations. So, if there is an index.html
in any of your locations on startup, it
is the home page of the application.
In addition to the “standard” static resource locations listed earlier, a special case
is made for Webjars content. Any resources with a path in
/webjars/**
are served from jar files if they are packaged in the Webjars format.
Spring WebFlux applications do not strictly depend on the Servlet API, so they
cannot be deployed as war files and do not use the src/main/webapp directory.
|
Template Engines
As well as REST web services, you can also use Spring WebFlux to serve dynamic HTML content. Spring WebFlux supports a variety of templating technologies, including Thymeleaf, FreeMarker, and Mustache.
Spring Boot includes auto-configuration support for the following templating engines:
When you use one of these templating engines with the default configuration, your
templates are picked up automatically from src/main/resources/templates
.
Error Handling
Spring Boot provides a WebExceptionHandler
that handles all errors in a sensible way.
Its position in the processing order is immediately before the handlers provided by
WebFlux, which are considered last. For machine clients, it produces a JSON response
with details of the error, the HTTP status, and the exception message. For browser
clients, there is a “whitelabel” error handler that renders the same data in HTML
format. You can also provide your own HTML templates to display errors (see the
next section).
The first step to customizing this feature often involves using the existing mechanism
but replacing or augmenting the error contents. For that, you can add a bean of type
ErrorAttributes
.
To change the error handling behavior, you can implement ErrorWebExceptionHandler
and
register a bean definition of that type. Because a WebExceptionHandler
is quite
low-level, Spring Boot also provides a convenient AbstractErrorWebExceptionHandler
to
let you handle errors in a WebFlux functional way, as shown in the following example:
public class CustomErrorWebExceptionHandler extends AbstractErrorWebExceptionHandler {
// Define constructor here
@Override
protected RouterFunction<ServerResponse> getRoutingFunction(ErrorAttributes errorAttributes) {
return RouterFunctions
.route(aPredicate, aHandler)
.andRoute(anotherPredicate, anotherHandler);
}
}
For a more complete picture, you can also subclass DefaultErrorWebExceptionHandler
directly and override specific methods.
Custom Error Pages
If you want to display a custom HTML error page for a given status code, you can add a
file to an /error
folder. Error pages can either be static HTML (that is, added under
any of the static resource folders) or built with templates. The name of the file should
be the exact status code or a series mask.
For example, to map 404
to a static HTML file, your folder structure would be as
follows:
src/
+- main/
+- java/
| + <source code>
+- resources/
+- public/
+- error/
| +- 404.html
+- <other public assets>
To map all 5xx
errors by using a Mustache template, your folder structure would be as
follows:
src/
+- main/
+- java/
| + <source code>
+- resources/
+- templates/
+- error/
| +- 5xx.mustache
+- <other templates>
Web Filters
Spring WebFlux provides a WebFilter
interface that can be implemented to filter HTTP
request-response exchanges. WebFilter
beans found in the application context will
be automatically used to filter each exchange.
Where the order of the filters is important they can implement Ordered
or be annotated
with @Order
. Spring Boot auto-configuration may configure web filters for you. When it
does so, the orders shown in the following table will be used:
Web Filter | Order |
---|---|
|
|
|
|
|
|
4.7.3. JAX-RS and Jersey
If you prefer the JAX-RS programming model for REST endpoints, you can use one of the
available implementations instead of Spring MVC. Jersey and
Apache CXF work quite well out of the box. CXF requires you to
register its Servlet
or Filter
as a @Bean
in your application context. Jersey has
some native Spring support, so we also provide auto-configuration support for it in
Spring Boot, together with a starter.
To get started with Jersey, include the spring-boot-starter-jersey
as a dependency
and then you need one @Bean
of type ResourceConfig
in which you register all the
endpoints, as shown in the following example:
@Component
public class JerseyConfig extends ResourceConfig {
public JerseyConfig() {
register(Endpoint.class);
}
}
Jersey’s support for scanning executable archives is rather limited. For example,
it cannot scan for endpoints in a package found in a fully executable jar file or in WEB-INF/classes when running an executable war file.
To avoid this limitation, the packages method should not be used, and endpoints should
be registered individually by using the register method, as shown in the preceding
example.
|
For more advanced customizations, you can also register an arbitrary number of beans that
implement ResourceConfigCustomizer
.
All the registered endpoints should be @Components
with HTTP resource annotations
(@GET
and others), as shown in the following example:
@Component
@Path("/hello")
public class Endpoint {
@GET
public String message() {
return "Hello";
}
}
Since the Endpoint
is a Spring @Component
, its lifecycle is managed by Spring and you
can use the @Autowired
annotation to inject dependencies and use the @Value
annotation to inject external configuration. By default, the Jersey servlet is registered
and mapped to /*
. You can change the mapping by adding @ApplicationPath
to your
ResourceConfig
.
By default, Jersey is set up as a Servlet in a @Bean
of type ServletRegistrationBean
named jerseyServletRegistration
. By default, the servlet is initialized lazily, but you
can customize that behavior by setting spring.jersey.servlet.load-on-startup
. You can
disable or override that bean by creating one of your own with the same name. You can
also use a filter instead of a servlet by setting spring.jersey.type=filter
(in which
case, the @Bean
to replace or override is jerseyFilterRegistration
). The filter has
an @Order
, which you can set with spring.jersey.filter.order
. Both the servlet and
the filter registrations can be given init parameters by using spring.jersey.init.*
to
specify a map of properties.
4.7.4. Embedded Servlet Container Support
Spring Boot includes support for embedded Tomcat,
Jetty, and
Undertow servers. Most developers use the
appropriate “Starter” to obtain a fully configured instance. By default, the embedded
server listens for HTTP requests on port 8080
.
Servlets, Filters, and listeners
When using an embedded servlet container, you can register servlets, filters, and all the
listeners (such as HttpSessionListener
) from the Servlet spec, either by using Spring
beans or by scanning for Servlet components.
Registering Servlets, Filters, and Listeners as Spring Beans
Any Servlet
, Filter
, or servlet *Listener
instance that is a Spring bean is
registered with the embedded container. This can be particularly convenient if you want
to refer to a value from your application.properties
during configuration.
By default, if the context contains only a single Servlet, it is mapped to /
. In the
case of multiple servlet beans, the bean name is used as a path prefix. Filters map to
/*
.
If convention-based mapping is not flexible enough, you can use the
ServletRegistrationBean
, FilterRegistrationBean
, and
ServletListenerRegistrationBean
classes for complete control.
Filter beans can be ordered to control their position in the filter chain by using
@Order
or implemented Ordered
. It is usually safe to leave Filter beans unordered.
However, if a specific order is required, you should avoid configuring a Filter that reads
the request body at Ordered.HIGHEST_PRECEDENCE
, since it might go against the character
encoding configuration of your application. If a Servlet filter wraps the request, it
should be configured with an order that is less than or equal to
OrderedFilter.REQUEST_WRAPPER_FILTER_MAX_ORDER
.
To see the order of every Filter in your application, enable debug level logging
for the web logging group
(logging.level.web=debug ). Details of the registered filters, including their order and
URL patterns, will then be logged at startup.
|
Servlet Context Initialization
Embedded servlet containers do not directly execute the Servlet 3.0+
javax.servlet.ServletContainerInitializer
interface or Spring’s
org.springframework.web.WebApplicationInitializer
interface. This is an intentional
design decision intended to reduce the risk that third party libraries designed to run
inside a war may break Spring Boot applications.
If you need to perform servlet context initialization in a Spring Boot application, you
should register a bean that implements the
org.springframework.boot.web.servlet.ServletContextInitializer
interface. The
single onStartup
method provides access to the ServletContext
and, if necessary, can
easily be used as an adapter to an existing WebApplicationInitializer
.
Scanning for Servlets, Filters, and listeners
When using an embedded container, automatic registration of classes annotated with
@WebServlet
, @WebFilter
, and @WebListener
can be enabled by using
@ServletComponentScan
.
@ServletComponentScan has no effect in a standalone container, where the
container’s built-in discovery mechanisms are used instead.
|
The ServletWebServerApplicationContext
Under the hood, Spring Boot uses a different type of ApplicationContext
for embedded
servlet container support. The ServletWebServerApplicationContext
is a special type of
WebApplicationContext
that bootstraps itself by searching for a single
ServletWebServerFactory
bean. Usually a TomcatServletWebServerFactory
,
JettyServletWebServerFactory
, or UndertowServletWebServerFactory
has been auto-configured.
You usually do not need to be aware of these implementation classes. Most
applications are auto-configured, and the appropriate ApplicationContext and
ServletWebServerFactory are created on your behalf.
|
Customizing Embedded Servlet Containers
Common servlet container settings can be configured by using Spring Environment
properties. Usually, you would define the properties in your application.properties
file.
Common server settings include:
-
Network settings: Listen port for incoming HTTP requests (
server.port
), interface address to bind toserver.address
, and so on. -
Session settings: Whether the session is persistent (
server.servlet.session.persistent
), session timeout (server.servlet.session.timeout
), location of session data (server.servlet.session.store-dir
), and session-cookie configuration (server.servlet.session.cookie.*
). -
Error management: Location of the error page (
server.error.path
) and so on.
Spring Boot tries as much as possible to expose common settings, but this is not always
possible. For those cases, dedicated namespaces offer server-specific customizations (see
server.tomcat
and server.undertow
). For instance,
access logs can be configured with specific
features of the embedded servlet container.
See the
ServerProperties class
for a complete list.
|
Programmatic Customization
If you need to programmatically configure your embedded servlet container, you can
register a Spring bean that implements the WebServerFactoryCustomizer
interface.
WebServerFactoryCustomizer
provides access to the
ConfigurableServletWebServerFactory
, which includes numerous customization setter
methods. The following example shows programmatically setting the port:
import org.springframework.boot.web.server.WebServerFactoryCustomizer;
import org.springframework.boot.web.servlet.server.ConfigurableServletWebServerFactory;
import org.springframework.stereotype.Component;
@Component
public class CustomizationBean implements WebServerFactoryCustomizer<ConfigurableServletWebServerFactory> {
@Override
public void customize(ConfigurableServletWebServerFactory server) {
server.setPort(9000);
}
}
TomcatServletWebServerFactory , JettyServletWebServerFactory and UndertowServletWebServerFactory
are dedicated variants of ConfigurableServletWebServerFactory that have additional customization setter methods
for Tomcat, Jetty and Undertow respectively.
|
Customizing ConfigurableServletWebServerFactory Directly
If the preceding customization techniques are too limited, you can register the
TomcatServletWebServerFactory
, JettyServletWebServerFactory
, or
UndertowServletWebServerFactory
bean yourself.
@Bean
public ConfigurableServletWebServerFactory webServerFactory() {
TomcatServletWebServerFactory factory = new TomcatServletWebServerFactory();
factory.setPort(9000);
factory.setSessionTimeout(10, TimeUnit.MINUTES);
factory.addErrorPages(new ErrorPage(HttpStatus.NOT_FOUND, "/notfound.html"));
return factory;
}
Setters are provided for many configuration options. Several protected method “hooks” are also provided should you need to do something more exotic. See the source code documentation for details.
JSP Limitations
When running a Spring Boot application that uses an embedded servlet container (and is packaged as an executable archive), there are some limitations in the JSP support.
-
With Jetty and Tomcat, it should work if you use war packaging. An executable war will work when launched with
java -jar
, and will also be deployable to any standard container. JSPs are not supported when using an executable jar. -
Undertow does not support JSPs.
-
Creating a custom
error.jsp
page does not override the default view for error handling. Custom error pages should be used instead.
4.7.5. Embedded Reactive Server Support
Spring Boot includes support for the following embedded reactive web servers: Reactor Netty, Tomcat, Jetty, and Undertow. Most developers use the appropriate “Starter” to obtain a fully configured instance. By default, the embedded server listens for HTTP requests on port 8080.
4.7.6. Reactive Server Resources Configuration
When auto-configuring a Reactor Netty or Jetty server, Spring Boot will create specific
beans that will provide HTTP resources to the server instance: ReactorResourceFactory
or JettyResourceFactory
.
By default, those resources will be also shared with the Reactor Netty and Jetty clients for optimal performances, given:
-
the same technology is used for server and client
-
the client instance is built using the
WebClient.Builder
bean auto-configured by Spring Boot
Developers can override the resource configuration for Jetty and Reactor Netty by providing
a custom ReactorResourceFactory
or JettyResourceFactory
bean - this will be applied to
both clients and servers.
You can learn more about the resource configuration on the client side in the WebClient Runtime section.
4.8. RSocket
RSocket is a binary protocol for use on byte stream transports. It enables symmetric interaction models via async message passing over a single connection.
Spring Framework, with the Spring Messaging module supports RSocket both on the server and
the client side. On the server side, it lets you create special @Controller
beans
to handle incoming RSocket messages.
Methods in your controller are mapped to RSocket routes by using @MessageMapping
annotations.
The following code shows a typical @Controller
:
@Controller
public class MyRSocketController {
@MessageMapping("chat.room.{name}")
public Flux<ChatMessages> enterChatRoom(@DestinationVariable String chatRoom,
Flux<ChatMessages> messages) {
// ...
}
@MessageMapping("users.\{user}.info")
Mono<ChatUserInfo> getUserInfo(@DestinationVariable String user) {
// ...
}
}
4.8.1. RSocket Strategies Auto-configuration
Spring Boot auto-configures an RSocketStrategies
bean that provides all the required
infrastructure for encoding and decoding RSocket payloads. By default, the
auto-configuration will try to configure the following (in order):
-
CBOR codecs with Jackson
-
JSON codecs with Jackson
The spring-boot-starter-rsocket
Starter provides both dependencies.
Developers can customize the RSocketStrategies
component by creating beans that
implement the RSocketStrategiesCustomizer
interface. Note that their @Order
is
important, as it determines the order of codecs.
4.8.2. RSocket server Auto-configuration
Spring Boot provides auto-configuration for RSocket servers. The required dependencies
are provided by the spring-boot-starter-rsocket
.
Spring Boot will start an RSocket server as a new embedded server in your application, or will plug the RSocket infrastructure into an existing reactive Web server. This depends on the type of application and its configuration.
In case of a WebFlux application (i.e. of type WebApplicationType.REACTIVE
), the
RSocket server will be plugged into the existing Web Server only if the following
properties match:
spring.rsocket.server.mapping-path=/rsocket # a mapping path is defined
spring.rsocket.server.transport=websocket # websocket is chosen as a transport
#spring.rsocket.server.port= # no port is defined
The only other way to create an RSocket server is to start an independent, embedded RSocket server. Besides the dependency requirements, the only required configuration is to define a port for that server:
spring.rsocket.server.port=9898 # the only required configuration
spring.rsocket.server.transport=tcp # you're free to configure other properties
4.8.3. Spring Messaging RSocket support
Spring Boot will auto-configure the Spring Messaging infrastructure for RSocket.
An RSocketStrategies
bean is created to provide encoding and decoding support
for RSocket messages. By default, Spring Boot will try to auto-configure JSON
support with Jackson for application/json
and "application/*+json"
media types.
Check out the Jackson support section to know more
about customization possibilities.
Developers can create RSocketStrategiesCustomizer
beans to add other strategies,
assuming there are Encoder
and Decoder
implementations available.
4.8.4. Calling RSocket Services with RSocketRequester
Once the RSocket
channel is established between server and client, any party can send or
receive requests to the other.
As a server, you can get injected an RSocketRequester
instance on any handler method of
an RSocket @Controller
. As a client, you need to configure and establish an RSocket
connection first. Spring Boot auto-configures an RSocketRequester.Builder
for such cases
with the expected codecs.
The RSocketRequester.Builder
instance is a prototype bean, meaning each injection point
will provide you with a new instance - this is done on purpose since this builder is stateful
and you shouldn’t create requesters with different setups using the same instance.
The following code shows a typical example:
@Service
public class MyService {
private final RSocketRequester rsocketRequester;
public MyService(RSocketRequester.Builder rsocketRequesterBuilder) {
this.rsocketRequester = rsocketRequesterBuilder
.connectTcp("example.org", 9090).block();
}
public Mono<User> someRSocketCall(String name) {
return this.requester.route("user").data(name)
.retrieveMono(User.class);
}
}
4.9. Security
If Spring Security is on the classpath, then web applications are
secured by default. Spring Boot relies on Spring Security’s content-negotiation strategy
to determine whether to use httpBasic
or formLogin
. To add method-level security to a
web application, you can also add @EnableGlobalMethodSecurity
with your desired
settings. Additional information can be found in the
Spring Security Reference Guide.
The default UserDetailsService
has a single user. The user name is user
, and the
password is random and is printed at INFO level when the application starts, as shown in
the following example:
Using generated security password: 78fa095d-3f4c-48b1-ad50-e24c31d5cf35
If you fine-tune your logging configuration, ensure that the
org.springframework.boot.autoconfigure.security category is set to log INFO -level
messages. Otherwise, the default password is not printed.
|
You can change the username and password by providing a spring.security.user.name
and
spring.security.user.password
.
The basic features you get by default in a web application are:
-
A
UserDetailsService
(orReactiveUserDetailsService
in case of a WebFlux application) bean with in-memory store and a single user with a generated password (seeSecurityProperties.User
for the properties of the user). -
Form-based login or HTTP Basic security (depending on the
Accept
header in the request) for the entire application (including actuator endpoints if actuator is on the classpath). -
A
DefaultAuthenticationEventPublisher
for publishing authentication events.
You can provide a different AuthenticationEventPublisher
by adding a bean for it.
4.9.1. MVC Security
The default security configuration is implemented in SecurityAutoConfiguration
and
UserDetailsServiceAutoConfiguration
. SecurityAutoConfiguration
imports
SpringBootWebSecurityConfiguration
for web security and
UserDetailsServiceAutoConfiguration
configures authentication, which is also
relevant in non-web applications. To switch off the default web application security
configuration completely, you can add a bean of type WebSecurityConfigurerAdapter
(doing
so does not disable the UserDetailsService
configuration or Actuator’s security).
To also switch off the UserDetailsService
configuration, you can add a bean of type
UserDetailsService
, AuthenticationProvider
, or AuthenticationManager
.
Access rules can be overridden by adding a custom WebSecurityConfigurerAdapter
. Spring
Boot provides convenience methods that can be used to override access rules for actuator
endpoints and static resources. EndpointRequest
can be used to create a RequestMatcher
that is based on the management.endpoints.web.base-path
property.
PathRequest
can be used to create a RequestMatcher
for resources in
commonly used locations.
4.9.2. WebFlux Security
Similar to Spring MVC applications, you can secure your WebFlux applications by adding
the spring-boot-starter-security
dependency. The default security configuration is
implemented in ReactiveSecurityAutoConfiguration
and
UserDetailsServiceAutoConfiguration
. ReactiveSecurityAutoConfiguration
imports
WebFluxSecurityConfiguration
for web security and UserDetailsServiceAutoConfiguration
configures authentication, which is also relevant in non-web applications. To switch off the default web application security
configuration completely, you can add a bean of type WebFilterChainProxy
(doing so does
not disable the UserDetailsService
configuration or Actuator’s security).
To also switch off the UserDetailsService
configuration, you can add a bean of type
ReactiveUserDetailsService
or ReactiveAuthenticationManager
.
Access rules can be configured by adding a custom SecurityWebFilterChain
. Spring
Boot provides convenience methods that can be used to override access rules for actuator
endpoints and static resources. EndpointRequest
can be used to create a
ServerWebExchangeMatcher
that is based on the management.endpoints.web.base-path
property.
PathRequest
can be used to create a ServerWebExchangeMatcher
for resources in
commonly used locations.
For example, you can customize your security configuration by adding something like:
@Bean
public SecurityWebFilterChain springSecurityFilterChain(ServerHttpSecurity http) {
return http
.authorizeExchange()
.matchers(PathRequest.toStaticResources().atCommonLocations()).permitAll()
.pathMatchers("/foo", "/bar")
.authenticated().and()
.formLogin().and()
.build();
}
4.9.3. OAuth2
OAuth2 is a widely used authorization framework that is supported by Spring.
Client
If you have spring-security-oauth2-client
on your classpath, you can take advantage of
some auto-configuration to make it easy to set up an OAuth2/Open ID Connect clients. This configuration
makes use of the properties under OAuth2ClientProperties
. The same properties are applicable to both servlet and reactive applications.
You can register multiple OAuth2 clients and providers under the
spring.security.oauth2.client
prefix, as shown in the following example:
spring.security.oauth2.client.registration.my-client-1.client-id=abcd
spring.security.oauth2.client.registration.my-client-1.client-secret=password
spring.security.oauth2.client.registration.my-client-1.client-name=Client for user scope
spring.security.oauth2.client.registration.my-client-1.provider=my-oauth-provider
spring.security.oauth2.client.registration.my-client-1.scope=user
spring.security.oauth2.client.registration.my-client-1.redirect-uri-template=https://my-redirect-uri.com
spring.security.oauth2.client.registration.my-client-1.client-authentication-method=basic
spring.security.oauth2.client.registration.my-client-1.authorization-grant-type=authorization_code
spring.security.oauth2.client.registration.my-client-2.client-id=abcd
spring.security.oauth2.client.registration.my-client-2.client-secret=password
spring.security.oauth2.client.registration.my-client-2.client-name=Client for email scope
spring.security.oauth2.client.registration.my-client-2.provider=my-oauth-provider
spring.security.oauth2.client.registration.my-client-2.scope=email
spring.security.oauth2.client.registration.my-client-2.redirect-uri-template=https://my-redirect-uri.com
spring.security.oauth2.client.registration.my-client-2.client-authentication-method=basic
spring.security.oauth2.client.registration.my-client-2.authorization-grant-type=authorization_code
spring.security.oauth2.client.provider.my-oauth-provider.authorization-uri=https://my-auth-server/oauth/authorize
spring.security.oauth2.client.provider.my-oauth-provider.token-uri=https://my-auth-server/oauth/token
spring.security.oauth2.client.provider.my-oauth-provider.user-info-uri=https://my-auth-server/userinfo
spring.security.oauth2.client.provider.my-oauth-provider.user-info-authentication-method=header
spring.security.oauth2.client.provider.my-oauth-provider.jwk-set-uri=https://my-auth-server/token_keys
spring.security.oauth2.client.provider.my-oauth-provider.user-name-attribute=name
For OpenID Connect providers that support OpenID Connect discovery,
the configuration can be further simplified. The provider needs to be configured with an issuer-uri
which is the
URI that the it asserts as its Issuer Identifier. For example, if the
issuer-uri
provided is "https://example.com", then an OpenID Provider Configuration Request
will be made to "https://example.com/.well-known/openid-configuration". The result is expected
to be an OpenID Provider Configuration Response
. The following example shows how an OpenID Connect
Provider can be configured with the issuer-uri
:
spring.security.oauth2.client.provider.oidc-provider.issuer-uri=https://dev-123456.oktapreview.com/oauth2/default/
By default, Spring Security’s OAuth2LoginAuthenticationFilter
only processes URLs
matching /login/oauth2/code/*
. If you want to customize the redirect-uri
to
use a different pattern, you need to provide configuration to process that custom pattern.
For example, for servlet applications, you can add your own WebSecurityConfigurerAdapter
that resembles the
following:
public class OAuth2LoginSecurityConfig extends WebSecurityConfigurerAdapter {
@Override
protected void configure(HttpSecurity http) throws Exception {
http
.authorizeRequests()
.anyRequest().authenticated()
.and()
.oauth2Login()
.redirectionEndpoint()
.baseUri("/custom-callback");
}
}
OAuth2 client registration for common providers
For common OAuth2 and OpenID providers, including Google, Github, Facebook, and Okta,
we provide a set of provider defaults (google
, github
, facebook
, and okta
,
respectively).
If you do not need to customize these providers, you can set the provider
attribute to
the one for which you need to infer defaults. Also, if the key for the client registration matches a
default supported provider, Spring Boot infers that as well.
In other words, the two configurations in the following example use the Google provider:
spring.security.oauth2.client.registration.my-client.client-id=abcd
spring.security.oauth2.client.registration.my-client.client-secret=password
spring.security.oauth2.client.registration.my-client.provider=google
spring.security.oauth2.client.registration.google.client-id=abcd
spring.security.oauth2.client.registration.google.client-secret=password
Resource Server
If you have spring-security-oauth2-resource-server
on your classpath, Spring Boot can
set up an OAuth2 Resource Server. For JWT configuration, a JWK Set URI or OIDC Issuer URI
needs to be specified, as shown in the following examples:
spring.security.oauth2.resourceserver.jwt.jwk-set-uri=https://example.com/oauth2/default/v1/keys
spring.security.oauth2.resourceserver.jwt.issuer-uri=https://dev-123456.oktapreview.com/oauth2/default/
If the authorization server does not support a JWK Set URI, you can configure the
resource server with the Public Key used for verifying the signature of the JWT. This can
be done using the spring.security.oauth2.resourceserver.jwt.public-key-location property,
where the value needs to point to a file containing the public key in the PEM-encoded x509
format.
|
The same properties are applicable for both servlet and reactive applications.
Alternatively, you can define your own JwtDecoder
bean for servlet applications
or a ReactiveJwtDecoder
for reactive applications.
In cases where opaque tokens are used instead of JWTs, you can configure the following properties to validate tokens via introspection:
spring.security.oauth2.resourceserver.opaquetoken.introspection-uri=https://example.com/check-token
spring.security.oauth2.resourceserver.opaquetoken.client-id=my-client-id
spring.security.oauth2.resourceserver.opaquetoken.client-secret-my-client-secret
Again, the same properties are applicable for both servlet and reactive applications.
Alternatively, you can define your own OAuth2TokenIntrospectionClient
bean for servlet applications
or a ReactiveOAuth2TokenIntrospectionClient
for reactive applications.
Authorization Server
Currently, Spring Security does not provide support for implementing an OAuth 2.0
Authorization Server. However, this functionality is available from
the Spring Security OAuth project,
which will eventually be superseded by Spring Security completely. Until then, you can
use the spring-security-oauth2-autoconfigure
module to easily set up an OAuth 2.0 authorization server;
see its documentation for instructions.
4.9.4. Actuator Security
For security purposes, all actuators other than /health
and /info
are disabled by
default. The management.endpoints.web.exposure.include
property can be used to enable
the actuators.
If Spring Security is on the classpath and no other WebSecurityConfigurerAdapter is
present, all actuators other than /health
and /info
are secured by Spring Boot
auto-configuration. If you define a custom WebSecurityConfigurerAdapter
, Spring Boot
auto-configuration will back off and you will be in full control of actuator access rules.
Before setting the management.endpoints.web.exposure.include , ensure that the
exposed actuators do not contain sensitive information and/or are secured by placing them
behind a firewall or by something like Spring Security.
|
Cross Site Request Forgery Protection
Since Spring Boot relies on Spring Security’s defaults, CSRF protection is turned on by
default. This means that the actuator endpoints that require a POST
(shutdown and
loggers endpoints), PUT
or DELETE
will get a 403 forbidden error when the default
security configuration is in use.
We recommend disabling CSRF protection completely only if you are creating a service that is used by non-browser clients. |
Additional information about CSRF protection can be found in the Spring Security Reference Guide.
4.10. Working with SQL Databases
The Spring Framework provides extensive support for working with SQL
databases, from direct JDBC access using JdbcTemplate
to complete “object relational
mapping” technologies such as Hibernate. Spring Data provides an
additional level of functionality: creating Repository
implementations directly from
interfaces and using conventions to generate queries from your method names.
4.10.1. Configure a DataSource
Java’s javax.sql.DataSource
interface provides a standard method of working with
database connections. Traditionally, a 'DataSource' uses a URL
along with some
credentials to establish a database connection.
See the “How-to” section for more advanced examples, typically to take full control over the configuration of the DataSource. |
Embedded Database Support
It is often convenient to develop applications by using an in-memory embedded database. Obviously, in-memory databases do not provide persistent storage. You need to populate your database when your application starts and be prepared to throw away data when your application ends.
The “How-to” section includes a section on how to initialize a database. |
Spring Boot can auto-configure embedded H2, HSQL, and Derby databases. You need not provide any connection URLs. You need only include a build dependency to the embedded database that you want to use.
If you are using this feature in your tests, you may notice that the same database is
reused by your whole test suite regardless of the number of application contexts that you
use. If you want to make sure that each context has a separate embedded database, you
should set |
For example, the typical POM dependencies would be as follows:
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-data-jpa</artifactId>
</dependency>
<dependency>
<groupId>org.hsqldb</groupId>
<artifactId>hsqldb</artifactId>
<scope>runtime</scope>
</dependency>
You need a dependency on spring-jdbc for an embedded database to be
auto-configured. In this example, it is pulled in transitively through
spring-boot-starter-data-jpa .
|
If, for whatever reason, you do configure the connection URL for an embedded
database, take care to ensure that the database’s automatic shutdown is disabled. If you
use H2, you should use DB_CLOSE_ON_EXIT=FALSE to do so. If you use HSQLDB, you should
ensure that shutdown=true is not used. Disabling the database’s automatic shutdown lets
Spring Boot control when the database is closed, thereby ensuring that it happens once
access to the database is no longer needed.
|
Connection to a Production Database
Production database connections can also be auto-configured by using a pooling
DataSource
. Spring Boot uses the following algorithm for choosing a specific
implementation:
-
We prefer HikariCP for its performance and concurrency. If HikariCP is available, we always choose it.
-
Otherwise, if the Tomcat pooling
DataSource
is available, we use it. -
If neither HikariCP nor the Tomcat pooling datasource are available and if Commons DBCP2 is available, we use it.
If you use the spring-boot-starter-jdbc
or spring-boot-starter-data-jpa
“starters”,
you automatically get a dependency to HikariCP
.
You can bypass that algorithm completely and specify the connection pool to use by
setting the spring.datasource.type property. This is especially important if you run
your application in a Tomcat container, as tomcat-jdbc is provided by default.
|
Additional connection pools can always be configured manually. If you define your
own DataSource bean, auto-configuration does not occur.
|
DataSource configuration is controlled by external configuration properties in
spring.datasource.*
. For example, you might declare the following section in
application.properties
:
spring.datasource.url=jdbc:mysql://localhost/test
spring.datasource.username=dbuser
spring.datasource.password=dbpass
spring.datasource.driver-class-name=com.mysql.jdbc.Driver
You should at least specify the URL by setting the spring.datasource.url
property. Otherwise, Spring Boot tries to auto-configure an embedded database.
|
You often do not need to specify the driver-class-name , since Spring Boot can
deduce it for most databases from the url .
|
For a pooling DataSource to be created, we need to be able to verify that a valid
Driver class is available, so we check for that before doing anything. In other words,
if you set spring.datasource.driver-class-name=com.mysql.jdbc.Driver , then that class
has to be loadable.
|
See
DataSourceProperties
for more of the supported options. These are the standard options that work regardless of
the actual implementation. It is also possible to fine-tune implementation-specific
settings by using their respective prefix (spring.datasource.hikari.*
,
spring.datasource.tomcat.*
, and spring.datasource.dbcp2.*
). Refer to the
documentation of the connection pool implementation you are using for more details.
For instance, if you use the Tomcat connection pool, you could customize many additional settings, as shown in the following example:
# Number of ms to wait before throwing an exception if no connection is available.
spring.datasource.tomcat.max-wait=10000
# Maximum number of active connections that can be allocated from this pool at the same time.
spring.datasource.tomcat.max-active=50
# Validate the connection before borrowing it from the pool.
spring.datasource.tomcat.test-on-borrow=true
Connection to a JNDI DataSource
If you deploy your Spring Boot application to an Application Server, you might want to configure and manage your DataSource by using your Application Server’s built-in features and access it by using JNDI.
The spring.datasource.jndi-name
property can be used as an alternative to the
spring.datasource.url
, spring.datasource.username
, and spring.datasource.password
properties to access the DataSource
from a specific JNDI location. For example, the
following section in application.properties
shows how you can access a JBoss AS defined
DataSource
:
spring.datasource.jndi-name=java:jboss/datasources/customers
4.10.2. Using JdbcTemplate
Spring’s JdbcTemplate
and NamedParameterJdbcTemplate
classes are auto-configured, and
you can @Autowire
them directly into your own beans, as shown in the following example:
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.jdbc.core.JdbcTemplate;
import org.springframework.stereotype.Component;
@Component
public class MyBean {
private final JdbcTemplate jdbcTemplate;
@Autowired
public MyBean(JdbcTemplate jdbcTemplate) {
this.jdbcTemplate = jdbcTemplate;
}
// ...
}
You can customize some properties of the template by using the spring.jdbc.template.*
properties, as shown in the following example:
spring.jdbc.template.max-rows=500
The NamedParameterJdbcTemplate reuses the same JdbcTemplate instance behind the
scenes. If more than one JdbcTemplate is defined and no primary candidate exists, the
NamedParameterJdbcTemplate is not auto-configured.
|
4.10.3. JPA and Spring Data JPA
The Java Persistence API is a standard technology that lets you “map” objects to
relational databases. The spring-boot-starter-data-jpa
POM provides a quick way to get
started. It provides the following key dependencies:
-
Hibernate: One of the most popular JPA implementations.
-
Spring Data JPA: Makes it easy to implement JPA-based repositories.
-
Spring ORMs: Core ORM support from the Spring Framework.
We do not go into too many details of JPA or Spring Data here. You can follow the “Accessing Data with JPA” guide from spring.io and read the Spring Data JPA and Hibernate reference documentation. |
Entity Classes
Traditionally, JPA “Entity” classes are specified in a persistence.xml
file. With
Spring Boot, this file is not necessary and “Entity Scanning” is used instead. By
default, all packages below your main configuration class (the one annotated with
@EnableAutoConfiguration
or @SpringBootApplication
) are searched.
Any classes annotated with @Entity
, @Embeddable
, or @MappedSuperclass
are
considered. A typical entity class resembles the following example:
package com.example.myapp.domain;
import java.io.Serializable;
import javax.persistence.*;
@Entity
public class City implements Serializable {
@Id
@GeneratedValue
private Long id;
@Column(nullable = false)
private String name;
@Column(nullable = false)
private String state;
// ... additional members, often include @OneToMany mappings
protected City() {
// no-args constructor required by JPA spec
// this one is protected since it shouldn't be used directly
}
public City(String name, String state) {
this.name = name;
this.state = state;
}
public String getName() {
return this.name;
}
public String getState() {
return this.state;
}
// ... etc
}
You can customize entity scanning locations by using the @EntityScan annotation.
See the “Separate @Entity Definitions from Spring Configuration”
how-to.
|
Spring Data JPA Repositories
Spring Data JPA repositories are interfaces that you can define to
access data. JPA queries are created automatically from your method names. For example, a
CityRepository
interface might declare a findAllByState(String state)
method to find
all the cities in a given state.
For more complex queries, you can annotate your method with Spring Data’s
Query
annotation.
Spring Data repositories usually extend from the
Repository
or
CrudRepository
interfaces. If you use auto-configuration, repositories are searched from the package
containing your main configuration class (the one annotated with
@EnableAutoConfiguration
or @SpringBootApplication
) down.
The following example shows a typical Spring Data repository interface definition:
package com.example.myapp.domain;
import org.springframework.data.domain.*;
import org.springframework.data.repository.*;
public interface CityRepository extends Repository<City, Long> {
Page<City> findAll(Pageable pageable);
City findByNameAndStateAllIgnoringCase(String name, String state);
}
Spring Data JPA repositories support three different modes of bootstrapping: default,
deferred, and lazy. To enable deferred or lazy bootstrapping, set the
spring.data.jpa.repositories.bootstrap-mode
to deferred
or lazy
respectively. When
using deferred or lazy bootstrapping, the auto-configured EntityManagerFactoryBuilder
will use the context’s AsyncTaskExecutor
, if any, as the bootstrap executor. If more
than one exists, the one named applicationTaskExecutor
will be used.
We have barely scratched the surface of Spring Data JPA. For complete details, see the Spring Data JPA reference documentation. |
Creating and Dropping JPA Databases
By default, JPA databases are automatically created only if you use an embedded
database (H2, HSQL, or Derby). You can explicitly configure JPA settings by using
spring.jpa.*
properties. For example, to create and drop tables you can add the
following line to your application.properties
:
spring.jpa.hibernate.ddl-auto=create-drop
Hibernate’s own internal property name for this (if you happen to remember it
better) is hibernate.hbm2ddl.auto . You can set it, along with other Hibernate native
properties, by using spring.jpa.properties.* (the prefix is stripped before adding
them to the entity manager). The following line shows an example of setting JPA
properties for Hibernate:
|
spring.jpa.properties.hibernate.globally_quoted_identifiers=true
The line in the preceding example passes a value of true
for the
hibernate.globally_quoted_identifiers
property to the Hibernate entity manager.
By default, the DDL execution (or validation) is deferred until the ApplicationContext
has started. There is also a spring.jpa.generate-ddl
flag, but it is not used if
Hibernate auto-configuration is active, because the ddl-auto
settings are more
fine-grained.
Open EntityManager in View
If you are running a web application, Spring Boot by default registers
OpenEntityManagerInViewInterceptor
to apply the “Open EntityManager in View” pattern, to allow for lazy loading in web
views. If you do not want this behavior, you should set spring.jpa.open-in-view
to
false
in your application.properties
.
4.10.4. Spring Data JDBC
Spring Data includes repository support for JDBC and will automatically generate SQL for
the methods on CrudRepository
. For more advanced queries, a @Query
annotation is
provided.
Spring Boot will auto-configure Spring Data’s JDBC repositories when the necessary
dependencies are on the classpath. They can be added to your project with a single
dependency on spring-boot-starter-data-jdbc
. If necessary, you can take control of
Spring Data JDBC’s configuration by adding the @EnableJdbcRepositories
annotation or a
JdbcConfiguration
subclass to your application.
For complete details of Spring Data JDBC, please refer to the reference documentation. |
4.10.5. Using H2’s Web Console
The H2 database provides a browser-based console that Spring Boot can auto-configure for you. The console is auto-configured when the following conditions are met:
-
You are developing a servlet-based web application.
-
com.h2database:h2
is on the classpath. -
You are using Spring Boot’s developer tools.
If you are not using Spring Boot’s developer tools but would still like to make use
of H2’s console, you can configure the spring.h2.console.enabled property with a value
of true .
|
The H2 console is only intended for use during development, so you should take
care to ensure that spring.h2.console.enabled is not set to true in production.
|
4.10.6. Using jOOQ
jOOQ Object Oriented Querying (jOOQ) is a popular product from Data Geekery which generates Java code from your database and lets you build type-safe SQL queries through its fluent API. Both the commercial and open source editions can be used with Spring Boot.
Code Generation
In order to use jOOQ type-safe queries, you need to generate Java classes from your
database schema. You can follow the instructions in the
jOOQ user manual. If you use the
jooq-codegen-maven
plugin and you also use the spring-boot-starter-parent
“parent POM”, you can safely omit the plugin’s <version>
tag. You can also use Spring
Boot-defined version variables (such as h2.version
) to declare the plugin’s database
dependency. The following listing shows an example:
<plugin>
<groupId>org.jooq</groupId>
<artifactId>jooq-codegen-maven</artifactId>
<executions>
...
</executions>
<dependencies>
<dependency>
<groupId>com.h2database</groupId>
<artifactId>h2</artifactId>
<version>${h2.version}</version>
</dependency>
</dependencies>
<configuration>
<jdbc>
<driver>org.h2.Driver</driver>
<url>jdbc:h2:~/yourdatabase</url>
</jdbc>
<generator>
...
</generator>
</configuration>
</plugin>
Using DSLContext
The fluent API offered by jOOQ is initiated through the org.jooq.DSLContext
interface.
Spring Boot auto-configures a DSLContext
as a Spring Bean and connects it to your
application DataSource
. To use the DSLContext
, you can @Autowire
it, as shown in
the following example:
@Component
public class JooqExample implements CommandLineRunner {
private final DSLContext create;
@Autowired
public JooqExample(DSLContext dslContext) {
this.create = dslContext;
}
}
The jOOQ manual tends to use a variable named create to hold the DSLContext .
|
You can then use the DSLContext
to construct your queries, as shown in the following
example:
public List<GregorianCalendar> authorsBornAfter1980() {
return this.create.selectFrom(AUTHOR)
.where(AUTHOR.DATE_OF_BIRTH.greaterThan(new GregorianCalendar(1980, 0, 1)))
.fetch(AUTHOR.DATE_OF_BIRTH);
}
jOOQ SQL Dialect
Unless the spring.jooq.sql-dialect
property has been configured, Spring Boot determines
the SQL dialect to use for your datasource. If Spring Boot could not detect the dialect,
it uses DEFAULT
.
Spring Boot can only auto-configure dialects supported by the open source version of jOOQ. |
Customizing jOOQ
More advanced customizations can be achieved by defining your own @Bean
definitions,
which is used when the jOOQ Configuration
is created. You can define beans for the
following jOOQ Types:
-
ConnectionProvider
-
ExecutorProvider
-
TransactionProvider
-
RecordMapperProvider
-
RecordUnmapperProvider
-
RecordListenerProvider
-
ExecuteListenerProvider
-
VisitListenerProvider
-
TransactionListenerProvider
You can also create your own org.jooq.Configuration
@Bean
if you want to take
complete control of the jOOQ configuration.
4.11. Working with NoSQL Technologies
Spring Data provides additional projects that help you access a variety of NoSQL technologies, including: MongoDB, Neo4J, Elasticsearch, Solr, Redis, Gemfire, Cassandra, Couchbase and LDAP. Spring Boot provides auto-configuration for Redis, MongoDB, Neo4j, Elasticsearch, Solr Cassandra, Couchbase, and LDAP. You can make use of the other projects, but you must configure them yourself. Refer to the appropriate reference documentation at projects.spring.io/spring-data.
4.11.1. Redis
Redis is a cache, message broker, and richly-featured key-value store. Spring Boot offers basic auto-configuration for the Lettuce and Jedis client libraries and the abstractions on top of them provided by Spring Data Redis.
There is a spring-boot-starter-data-redis
“Starter” for collecting the dependencies
in a convenient way. By default, it uses
Lettuce. That starter handles both
traditional and reactive applications.
we also provide a spring-boot-starter-data-redis-reactive “Starter” for
consistency with the other stores with reactive support.
|
Connecting to Redis
You can inject an auto-configured RedisConnectionFactory
, StringRedisTemplate
, or
vanilla RedisTemplate
instance as you would any other Spring Bean. By default, the
instance tries to connect to a Redis server at localhost:6379
. The following listing
shows an example of such a bean:
@Component
public class MyBean {
private StringRedisTemplate template;
@Autowired
public MyBean(StringRedisTemplate template) {
this.template = template;
}
// ...
}
You can also register an arbitrary number of beans that implement
LettuceClientConfigurationBuilderCustomizer for more advanced customizations. If you
use Jedis, JedisClientConfigurationBuilderCustomizer is also available.
|
If you add your own @Bean
of any of the auto-configured types, it replaces the default
(except in the case of RedisTemplate
, when the exclusion is based on the bean name,
redisTemplate
, not its type). By default, if commons-pool2
is on the classpath, you
get a pooled connection factory.
4.11.2. MongoDB
MongoDB is an open-source NoSQL document database that uses a
JSON-like schema instead of traditional table-based relational data. Spring Boot offers
several conveniences for working with MongoDB, including the
spring-boot-starter-data-mongodb
and spring-boot-starter-data-mongodb-reactive
“Starters”.
Connecting to a MongoDB Database
To access Mongo databases, you can inject an auto-configured
org.springframework.data.mongodb.MongoDbFactory
. By default, the instance tries to
connect to a MongoDB server at mongodb://localhost/test
The following example shows how
to connect to a MongoDB database:
import org.springframework.data.mongodb.MongoDbFactory;
import com.mongodb.DB;
@Component
public class MyBean {
private final MongoDbFactory mongo;
@Autowired
public MyBean(MongoDbFactory mongo) {
this.mongo = mongo;
}
// ...
public void example() {
DB db = mongo.getDb();
// ...
}
}
You can set the spring.data.mongodb.uri
property to change the URL and configure
additional settings such as the replica set, as shown in the following example:
spring.data.mongodb.uri=mongodb://user:[email protected]:12345,mongo2.example.com:23456/test
Alternatively, as long as you use Mongo 2.x, you can specify a host
/port
. For
example, you might declare the following settings in your application.properties
:
spring.data.mongodb.host=mongoserver
spring.data.mongodb.port=27017
If you have defined your own MongoClient
, it will be used to auto-configure a suitable
MongoDbFactory
. Both com.mongodb.MongoClient
and com.mongodb.client.MongoClient
are supported.
If you use the Mongo 3.0 Java driver, spring.data.mongodb.host and
spring.data.mongodb.port are not supported. In such cases, spring.data.mongodb.uri
should be used to provide all of the configuration.
|
If spring.data.mongodb.port is not specified, the default of 27017 is used. You
could delete this line from the example shown earlier.
|
If you do not use Spring Data Mongo, you can inject com.mongodb.MongoClient beans
instead of using MongoDbFactory . If you want to take complete control of establishing
the MongoDB connection, you can also declare your own MongoDbFactory or MongoClient
bean.
|
If you are using the reactive driver, Netty is required for SSL. The auto-configuration configures this factory automatically if Netty is available and the factory to use hasn’t been customized already. |
MongoTemplate
Spring Data MongoDB provides a
MongoTemplate
class that is very
similar in its design to Spring’s JdbcTemplate
. As with JdbcTemplate
, Spring Boot
auto-configures a bean for you to inject the template, as follows:
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.data.mongodb.core.MongoTemplate;
import org.springframework.stereotype.Component;
@Component
public class MyBean {
private final MongoTemplate mongoTemplate;
@Autowired
public MyBean(MongoTemplate mongoTemplate) {
this.mongoTemplate = mongoTemplate;
}
// ...
}
See the
MongoOperations
Javadoc for complete details.
Spring Data MongoDB Repositories
Spring Data includes repository support for MongoDB. As with the JPA repositories discussed earlier, the basic principle is that queries are constructed automatically, based on method names.
In fact, both Spring Data JPA and Spring Data MongoDB share the same common
infrastructure. You could take the JPA example from earlier and, assuming that City
is
now a Mongo data class rather than a JPA @Entity
, it works in the same way, as shown
in the following example:
package com.example.myapp.domain;
import org.springframework.data.domain.*;
import org.springframework.data.repository.*;
public interface CityRepository extends Repository<City, Long> {
Page<City> findAll(Pageable pageable);
City findByNameAndStateAllIgnoringCase(String name, String state);
}
You can customize document scanning locations by using the @EntityScan annotation.
|
For complete details of Spring Data MongoDB, including its rich object mapping technologies, refer to its reference documentation. |
Embedded Mongo
Spring Boot offers auto-configuration for
Embedded Mongo. To use it in
your Spring Boot application, add a dependency on
de.flapdoodle.embed:de.flapdoodle.embed.mongo
.
The port that Mongo listens on can be configured by setting the spring.data.mongodb.port
property. To use a randomly allocated free port, use a value of 0. The MongoClient
created by MongoAutoConfiguration
is automatically configured to use the randomly
allocated port.
If you do not configure a custom port, the embedded support uses a random port (rather than 27017) by default. |
If you have SLF4J on the classpath, the output produced by Mongo is automatically routed
to a logger named org.springframework.boot.autoconfigure.mongo.embedded.EmbeddedMongo
.
You can declare your own IMongodConfig
and IRuntimeConfig
beans to take control of
the Mongo instance’s configuration and logging routing. The download configuration can be
customized by declaring a DownloadConfigBuilderCustomizer
bean.
4.11.3. Neo4j
Neo4j is an open-source NoSQL graph database that uses a rich data
model of nodes connected by first class relationships, which is better suited for
connected big data than traditional RDBMS approaches. Spring Boot offers several
conveniences for working with Neo4j, including the spring-boot-starter-data-neo4j
“Starter”.
Connecting to a Neo4j Database
To access a Neo4j server, you can inject an auto-configured
org.neo4j.ogm.session.Session
. By default, the instance tries to connect to a Neo4j
server at localhost:7687
using the Bolt protocol. The following example shows how to
inject a Neo4j Session
:
@Component
public class MyBean {
private final Session session;
@Autowired
public MyBean(Session session) {
this.session = session;
}
// ...
}
You can configure the uri and credentials to use by setting the spring.data.neo4j.*
properties, as shown in the following example:
spring.data.neo4j.uri=bolt://my-server:7687
spring.data.neo4j.username=neo4j
spring.data.neo4j.password=secret
You can take full control over the session creation by either adding a
org.neo4j.ogm.config.Configuration
bean or a org.neo4j.ogm.session.SessionFactory
bean.
Using the Embedded Mode
If you add org.neo4j:neo4j-ogm-embedded-driver
to the dependencies of your application,
Spring Boot automatically configures an in-process embedded instance of Neo4j that does
not persist any data when your application shuts down.
As the embedded Neo4j OGM driver does not provide the Neo4j kernel itself, you have
to declare |
The embedded driver takes precedence over the other drivers when there are multiple
drivers on the classpath. You can explicitly disable the embedded mode by setting
spring.data.neo4j.embedded.enabled=false
.
Data Neo4j Tests automatically make use of an embedded Neo4j instance if the embedded driver and Neo4j kernel are on the classpath as described above.
You can enable persistence for the embedded mode by providing a path to a database file
in your configuration, e.g. |
Using Native Types
Neo4j-OGM can map some types, like those in java.time.*
, to String
-based properties
or to one of the native types that Neo4j provides. For backwards compatibility reasons
the default for Neo4j-OGM is to use a String
-based representation. To use native types,
add a dependency on either org.neo4j:neo4j-ogm-bolt-native-types
or
org.neo4j:neo4j-ogm-embedded-native-types
, and configure the
spring.data.neo4j.use-native-types
property as shown in the following example:
spring.data.neo4j.use-native-types=true
Neo4jSession
By default, if you are running a web application, the session is bound to the thread for
the entire processing of the request (that is, it uses the "Open Session in View"
pattern). If you do not want this behavior, add the following line to your
application.properties
file:
spring.data.neo4j.open-in-view=false
Spring Data Neo4j Repositories
Spring Data includes repository support for Neo4j.
Spring Data Neo4j shares the common infrastructure with Spring Data JPA as many other
Spring Data modules do. You could take the JPA example from earlier and define
City
as Neo4j OGM @NodeEntity
rather than JPA @Entity
and the repository
abstraction works in the same way, as shown in the following example:
package com.example.myapp.domain;
import java.util.Optional;
import org.springframework.data.neo4j.repository.*;
public interface CityRepository extends Neo4jRepository<City, Long> {
Optional<City> findOneByNameAndState(String name, String state);
}
The spring-boot-starter-data-neo4j
“Starter” enables the repository support as well
as transaction management. You can customize the locations to look for repositories and
entities by using @EnableNeo4jRepositories
and @EntityScan
respectively on a
@Configuration
-bean.
For complete details of Spring Data Neo4j, including its object mapping technologies, refer to the reference documentation. |
4.11.4. Gemfire
Spring Data Gemfire provides
convenient Spring-friendly tools for accessing the
Pivotal Gemfire data management
platform. There is a spring-boot-starter-data-gemfire
“Starter” for collecting the
dependencies in a convenient way. There is currently no auto-configuration support for
Gemfire, but you can enable Spring Data Repositories with a
single annotation: @EnableGemfireRepositories
.
4.11.5. Solr
Apache Solr is a search engine. Spring Boot offers basic
auto-configuration for the Solr 5 client library and the abstractions on top of it
provided by Spring Data Solr. There
is a spring-boot-starter-data-solr
“Starter” for collecting the dependencies in a
convenient way.
Connecting to Solr
You can inject an auto-configured SolrClient
instance as you would any other Spring
bean. By default, the instance tries to connect to a server at
localhost:8983/solr
. The following example shows how to inject a Solr bean:
@Component
public class MyBean {
private SolrClient solr;
@Autowired
public MyBean(SolrClient solr) {
this.solr = solr;
}
// ...
}
If you add your own @Bean
of type SolrClient
, it replaces the default.
Spring Data Solr Repositories
Spring Data includes repository support for Apache Solr. As with the JPA repositories discussed earlier, the basic principle is that queries are automatically constructed for \ you based on method names.
In fact, both Spring Data JPA and Spring Data Solr share the same common infrastructure.
You could take the JPA example from earlier and, assuming that City
is now a
@SolrDocument
class rather than a JPA @Entity
, it works in the same way.
For complete details of Spring Data Solr, refer to the reference documentation. |
4.11.6. Elasticsearch
Elasticsearch is an open source, distributed, RESTful search and analytics engine. Spring Boot offers basic auto-configuration for Elasticsearch.
Spring Boot supports several clients:
-
The official Java "Low Level" and "High Level" REST clients
-
The
ReactiveElasticsearchClient
provided by Spring Data Elasticsearch
The transport client is still available but its support has been deprecated in
Spring Data Elasticsearch
and Elasticsearch itself. It will be removed in a future release.
Spring Boot provides a dedicated “Starter”, spring-boot-starter-data-elasticsearch
.
The Jest client has been deprecated as well, since both Elasticsearch and Spring Data Elasticsearch provide official support for REST clients.
Connecting to Elasticsearch using REST clients
Elasticsearch ships two different REST clients that you can use to query a cluster: the "Low Level" client and the "High Level" client.
If you have the org.elasticsearch.client:elasticsearch-rest-client
dependency on the
classpath, Spring Boot will auto-configure and register a RestClient
bean that
by default targets localhost:9200
.
You can further tune how RestClient
is configured, as shown in the following example:
spring.elasticsearch.rest.uris=https://search.example.com:9200
spring.elasticsearch.rest.read-timeout=10s
spring.elasticsearch.rest.username=user
spring.elasticsearch.rest.password=secret
You can also register an arbitrary number of beans that implement
RestClientBuilderCustomizer
for more advanced customizations.
To take full control over the registration, define a RestClient
bean.
If you have the org.elasticsearch.client:elasticsearch-rest-high-level-client
dependency
on the classpath, Spring Boot will auto-configure a RestHighLevelClient
, which wraps
any existing RestClient
bean, reusing its HTTP configuration.
Connecting to Elasticsearch using Reactive REST clients
Spring Data Elasticsearch ships ReactiveElasticsearchClient
for querying Elasticsearch instances in a reactive fashion. It is built on top of WebFlux’s
WebClient
, so both spring-boot-starter-elasticsearch
and spring-boot-starter-webflux
dependencies are useful to enable this support.
By default, Spring Boot will auto-configure and register a ReactiveElasticsearchClient
bean that targets localhost:9200
.
You can further tune how it is configured, as shown in the following example:
spring.elasticsearch.reactive.endpoints=search.example.com:9200
spring.elasticsearch.reactive.use-ssl=true
spring.elasticsearch.reactive.socket-timeout=10s
spring.elasticsearch.reactive.username=user
spring.elasticsearch.reactive.password=secret
If the configuration properties are not enough and you’d like to fully control the client
configuration, you can register a custom ClientConfiguration
bean.
Connecting to Elasticsearch using Jest
Now that Spring Boot supports the official RestHighLevelClient
, Jest support is
deprecated.
If you have Jest
on the classpath, you can inject an auto-configured JestClient
that
by default targets localhost:9200
. You can further tune how the client is
configured, as shown in the following example:
spring.elasticsearch.jest.uris=https://search.example.com:9200
spring.elasticsearch.jest.read-timeout=10000
spring.elasticsearch.jest.username=user
spring.elasticsearch.jest.password=secret
You can also register an arbitrary number of beans that implement
HttpClientConfigBuilderCustomizer
for more advanced customizations. The following
example tunes additional HTTP settings:
static class HttpSettingsCustomizer implements HttpClientConfigBuilderCustomizer {
@Override
public void customize(HttpClientConfig.Builder builder) {
builder.maxTotalConnection(100).defaultMaxTotalConnectionPerRoute(5);
}
}
To take full control over the registration, define a JestClient
bean.
Connecting to Elasticsearch by Using Spring Data
To connect to Elasticsearch, a RestHighLevelClient
bean must be defined,
auto-configured by Spring Boot or manually provided by the application (see previous sections).
With this configuration in place, an
ElasticsearchRestTemplate
can be injected like any other Spring bean,
as shown in the following example:
@Component
public class MyBean {
private final ElasticsearchRestTemplate template;
public MyBean(ElasticsearchRestTemplate template) {
this.template = template;
}
// ...
}
In the presence of spring-data-elasticsearch
and the required dependencies
for using a WebClient
(typically spring-boot-starter-webflux
), Spring Boot can also
auto-configure a
ReactiveElasticsearchClient
and a ReactiveElasticsearchTemplate
as beans. They are the reactive equivalent of the
other REST clients.
Spring Data Elasticsearch Repositories
Spring Data includes repository support for Elasticsearch. As with the JPA repositories discussed earlier, the basic principle is that queries are constructed for you automatically based on method names.
In fact, both Spring Data JPA and Spring Data Elasticsearch share the same common
infrastructure. You could take the JPA example from earlier and, assuming that City
is
now an Elasticsearch @Document
class rather than a JPA @Entity
, it works in the same
way.
For complete details of Spring Data Elasticsearch, refer to the reference documentation. |
Spring Boot supports both classic and reactive Elasticsearch repositories, using the
ElasticsearchRestTemplate
or ReactiveElasticsearchTemplate
beans. Most likely those
beans are auto-configured by Spring Boot given the required dependencies are present.
If you wish to use your own template for backing the Elasticsearch repositories, you can
add your own ElasticsearchRestTemplate
or ElasticsearchOperations
@Bean
,
as long as it is named "elasticsearchTemplate"
. Same applies to
ReactiveElasticsearchTemplate
and ReactiveElasticsearchOperations
, with the bean
name "reactiveElasticsearchTemplate"
.
You can choose to disable the repositories support with the following property:
spring.data.elasticsearch.repositories.enabled=false
4.11.7. Cassandra
Cassandra is an open source, distributed database
management system designed to handle large amounts of data across many commodity servers.
Spring Boot offers auto-configuration for Cassandra and the abstractions on top of it
provided by Spring Data
Cassandra. There is a spring-boot-starter-data-cassandra
“Starter” for collecting
the dependencies in a convenient way.
Connecting to Cassandra
You can inject an auto-configured CassandraTemplate
or a Cassandra Session
instance
as you would with any other Spring Bean. The spring.data.cassandra.*
properties can be
used to customize the connection. Generally, you provide keyspace-name
and
contact-points
properties, as shown in the following example:
spring.data.cassandra.keyspace-name=mykeyspace
spring.data.cassandra.contact-points=cassandrahost1,cassandrahost2
You can also register an arbitrary number of beans that implement
ClusterBuilderCustomizer
for more advanced customizations.
The following code listing shows how to inject a Cassandra bean:
@Component
public class MyBean {
private CassandraTemplate template;
@Autowired
public MyBean(CassandraTemplate template) {
this.template = template;
}
// ...
}
If you add your own @Bean
of type CassandraTemplate
, it replaces the default.
Spring Data Cassandra Repositories
Spring Data includes basic repository support for Cassandra. Currently, this is more
limited than the JPA repositories discussed earlier and needs to annotate finder methods
with @Query
.
For complete details of Spring Data Cassandra, refer to the reference documentation. |
4.11.8. Couchbase
Couchbase is an open-source, distributed, multi-model NoSQL
document-oriented database that is optimized for interactive applications. Spring Boot
offers auto-configuration for Couchbase and the abstractions on top of it provided by
Spring Data Couchbase. There are
spring-boot-starter-data-couchbase
and spring-boot-starter-data-couchbase-reactive
“Starters” for collecting the dependencies in a convenient way.
Connecting to Couchbase
You can get a Bucket
and Cluster
by adding the Couchbase SDK and some configuration.
The spring.couchbase.*
properties can be used to customize the connection. Generally,
you provide the bootstrap hosts, bucket name, and password, as shown in the following
example:
spring.couchbase.bootstrap-hosts=my-host-1,192.168.1.123
spring.couchbase.bucket.name=my-bucket
spring.couchbase.bucket.password=secret
You need to provide at least the bootstrap host(s), in which case the bucket name is
|
It is also possible to customize some of the CouchbaseEnvironment
settings. For
instance, the following configuration changes the timeout to use to open a new Bucket
and enables SSL support:
spring.couchbase.env.timeouts.connect=3000
spring.couchbase.env.ssl.key-store=/location/of/keystore.jks
spring.couchbase.env.ssl.key-store-password=secret
Check the spring.couchbase.env.*
properties for more details.
Spring Data Couchbase Repositories
Spring Data includes repository support for Couchbase. For complete details of Spring Data Couchbase, refer to the reference documentation.
You can inject an auto-configured CouchbaseTemplate
instance as you would with any
other Spring Bean, provided a default CouchbaseConfigurer
is available (which
happens when you enable Couchbase support, as explained earlier).
The following examples shows how to inject a Couchbase bean:
@Component
public class MyBean {
private final CouchbaseTemplate template;
@Autowired
public MyBean(CouchbaseTemplate template) {
this.template = template;
}
// ...
}
There are a few beans that you can define in your own configuration to override those provided by the auto-configuration:
-
A
CouchbaseTemplate
@Bean
with a name ofcouchbaseTemplate
. -
An
IndexManager
@Bean
with a name ofcouchbaseIndexManager
. -
A
CustomConversions
@Bean
with a name ofcouchbaseCustomConversions
.
To avoid hard-coding those names in your own config, you can reuse BeanNames
provided
by Spring Data Couchbase. For instance, you can customize the converters to use, as
follows:
@Configuration(proxyBeanMethods = false)
public class SomeConfiguration {
@Bean(BeanNames.COUCHBASE_CUSTOM_CONVERSIONS)
public CustomConversions myCustomConversions() {
return new CustomConversions(...);
}
// ...
}
If you want to fully bypass the auto-configuration for Spring Data Couchbase,
provide your own implementation of
org.springframework.data.couchbase.config.AbstractCouchbaseDataConfiguration .
|
4.11.9. LDAP
LDAP (Lightweight Directory Access Protocol) is an open, vendor-neutral, industry standard application protocol for accessing and maintaining distributed directory information services over an IP network. Spring Boot offers auto-configuration for any compliant LDAP server as well as support for the embedded in-memory LDAP server from UnboundID.
LDAP abstractions are provided by
Spring Data LDAP.
There is a spring-boot-starter-data-ldap
“Starter” for collecting the dependencies in
a convenient way.
Connecting to an LDAP Server
To connect to an LDAP server, make sure you declare a dependency on the
spring-boot-starter-data-ldap
“Starter” or spring-ldap-core
and then declare the
URLs of your server in your application.properties, as shown in the following example:
spring.ldap.urls=ldap://myserver:1235
spring.ldap.username=admin
spring.ldap.password=secret
If you need to customize connection settings, you can use the spring.ldap.base
and
spring.ldap.base-environment
properties.
An LdapContextSource
is auto-configured based on these settings. If you need to customize
it, for instance to use a PooledContextSource
, you can still inject the auto-configured
LdapContextSource
. Make sure to flag your customized ContextSource
as @Primary
so
that the auto-configured LdapTemplate
uses it.
Spring Data LDAP Repositories
Spring Data includes repository support for LDAP. For complete details of Spring Data LDAP, refer to the reference documentation.
You can also inject an auto-configured LdapTemplate
instance as you would with any
other Spring Bean, as shown in the following example:
@Component
public class MyBean {
private final LdapTemplate template;
@Autowired
public MyBean(LdapTemplate template) {
this.template = template;
}
// ...
}
Embedded In-memory LDAP Server
For testing purposes, Spring Boot supports auto-configuration of an in-memory LDAP server
from UnboundID. To configure the server,
add a dependency to com.unboundid:unboundid-ldapsdk
and declare a base-dn
property, as
follows:
spring.ldap.embedded.base-dn=dc=spring,dc=io
It is possible to define multiple base-dn values, however, since distinguished names usually contain commas, they must be defined using the correct notation. In yaml files, you can use the yaml list notation:
In properties files, you must include the index as part of the property name:
|
By default, the server starts on a random port and triggers the regular LDAP support.
There is no need to specify a spring.ldap.urls
property.
If there is a schema.ldif
file on your classpath, it is used to initialize the server.
If you want to load the initialization script from a different resource, you can also use
the spring.ldap.embedded.ldif
property.
By default, a standard schema is used to validate LDIF
files. You can turn off
validation altogether by setting the spring.ldap.embedded.validation.enabled
property.
If you have custom attributes, you can use spring.ldap.embedded.validation.schema
to
define your custom attribute types or object classes.
4.11.10. InfluxDB
InfluxDB is an open-source time series database optimized for fast, high-availability storage and retrieval of time series data in fields such as operations monitoring, application metrics, Internet-of-Things sensor data, and real-time analytics.
Connecting to InfluxDB
Spring Boot auto-configures an InfluxDB
instance, provided the influxdb-java
client
is on the classpath and the URL of the database is set, as shown in the following
example:
spring.influx.url=https://172.0.0.1:8086
If the connection to InfluxDB requires a user and password, you can set the
spring.influx.user
and spring.influx.password
properties accordingly.
InfluxDB relies on OkHttp. If you need to tune the http client InfluxDB
uses behind the
scenes, you can register an InfluxDbOkHttpClientBuilderProvider
bean.
4.12. Caching
The Spring Framework provides support for transparently adding caching to an application.
At its core, the abstraction applies caching to methods, thus reducing the number of
executions based on the information available in the cache. The caching logic is applied
transparently, without any interference to the invoker. Spring Boot auto-configures the
cache infrastructure as long as caching support is enabled via the @EnableCaching
annotation.
Check the relevant section of the Spring Framework reference for more details. |
In a nutshell, adding caching to an operation of your service is as easy as adding the relevant annotation to its method, as shown in the following example:
import org.springframework.cache.annotation.Cacheable;
import org.springframework.stereotype.Component;
@Component
public class MathService {
@Cacheable("piDecimals")
public int computePiDecimal(int i) {
// ...
}
}
This example demonstrates the use of caching on a potentially costly operation. Before
invoking computePiDecimal
, the abstraction looks for an entry in the piDecimals
cache
that matches the i
argument. If an entry is found, the content in the cache is
immediately returned to the caller, and the method is not invoked. Otherwise, the method
is invoked, and the cache is updated before returning the value.
You can also use the standard JSR-107 (JCache) annotations (such as
@CacheResult ) transparently. However, we strongly advise you to not mix and match the
Spring Cache and JCache annotations.
|
If you do not add any specific cache library, Spring Boot auto-configures a
simple provider that uses concurrent maps in
memory. When a cache is required (such as piDecimals
in the preceding example), this
provider creates it for you. The simple provider is not really recommended for
production usage, but it is great for getting started and making sure that you understand
the features. When you have made up your mind about the cache provider to use, please
make sure to read its documentation to figure out how to configure the caches that your
application uses. Nearly all providers require you to explicitly configure every cache
that you use in the application. Some offer a way to customize the default caches defined
by the spring.cache.cache-names
property.
4.12.1. Supported Cache Providers
The cache abstraction does not provide an actual store and relies on abstraction
materialized by the org.springframework.cache.Cache
and
org.springframework.cache.CacheManager
interfaces.
If you have not defined a bean of type CacheManager
or a CacheResolver
named
cacheResolver
(see
CachingConfigurer
),
Spring Boot tries to detect the following providers (in the indicated order):
-
JCache (JSR-107) (EhCache 3, Hazelcast, Infinispan, and others)
It is also possible to force a particular cache provider by setting the
spring.cache.type property. Use this property if you need to
disable caching altogether in certain environment
(such as tests).
|
Use the spring-boot-starter-cache “Starter” to quickly add basic caching
dependencies. The starter brings in spring-context-support . If you add dependencies
manually, you must include spring-context-support in order to use the JCache,
EhCache 2.x, or Caffeine support.
|
If the CacheManager
is auto-configured by Spring Boot, you can further tune its
configuration before it is fully initialized by exposing a bean that implements the
CacheManagerCustomizer
interface. The following example sets a flag to say that null
values should be passed down to the underlying map:
@Bean
public CacheManagerCustomizer<ConcurrentMapCacheManager> cacheManagerCustomizer() {
return new CacheManagerCustomizer<ConcurrentMapCacheManager>() {
@Override
public void customize(ConcurrentMapCacheManager cacheManager) {
cacheManager.setAllowNullValues(false);
}
};
}
In the preceding example, an auto-configured |
Generic
Generic caching is used if the context defines at least one
org.springframework.cache.Cache
bean. A CacheManager
wrapping all beans of that type
is created.
JCache (JSR-107)
JCache is bootstrapped through the presence of a
javax.cache.spi.CachingProvider
on the classpath (that is, a JSR-107 compliant caching
library exists on the classpath), and the JCacheCacheManager
is provided by the
spring-boot-starter-cache
“Starter”. Various compliant libraries are available, and
Spring Boot provides dependency management for Ehcache 3, Hazelcast, and Infinispan. Any
other compliant library can be added as well.
It might happen that more than one provider is present, in which case the provider must be explicitly specified. Even if the JSR-107 standard does not enforce a standardized way to define the location of the configuration file, Spring Boot does its best to accommodate setting a cache with implementation details, as shown in the following example:
# Only necessary if more than one provider is present
spring.cache.jcache.provider=com.acme.MyCachingProvider
spring.cache.jcache.config=classpath:acme.xml
When a cache library offers both a native implementation and JSR-107 support, Spring Boot prefers the JSR-107 support, so that the same features are available if you switch to a different JSR-107 implementation. |
Spring Boot has general support for Hazelcast. If a
single HazelcastInstance is available, it is automatically reused for the
CacheManager as well, unless the spring.cache.jcache.config property is specified.
|
There are two ways to customize the underlying javax.cache.cacheManager
:
-
Caches can be created on startup by setting the
spring.cache.cache-names
property. If a customjavax.cache.configuration.Configuration
bean is defined, it is used to customize them. -
org.springframework.boot.autoconfigure.cache.JCacheManagerCustomizer
beans are invoked with the reference of theCacheManager
for full customization.
If a standard javax.cache.CacheManager bean is defined, it is wrapped
automatically in an org.springframework.cache.CacheManager implementation that the
abstraction expects. No further customization is applied to it.
|
EhCache 2.x
EhCache 2.x is used if a file named ehcache.xml
can be found at
the root of the classpath. If EhCache 2.x is found, the EhCacheCacheManager
provided by
the spring-boot-starter-cache
“Starter” is used to bootstrap the cache manager. An
alternate configuration file can be provided as well, as shown in the following example:
spring.cache.ehcache.config=classpath:config/another-config.xml
Hazelcast
Spring Boot has general support for Hazelcast. If a
HazelcastInstance
has been auto-configured, it is automatically wrapped in a
CacheManager
.
Infinispan
Infinispan has no default configuration file location, so it must be specified explicitly. Otherwise, the default bootstrap is used.
spring.cache.infinispan.config=infinispan.xml
Caches can be created on startup by setting the spring.cache.cache-names
property. If a
custom ConfigurationBuilder
bean is defined, it is used to customize the caches.
The support of Infinispan in Spring Boot is restricted to the embedded mode and is quite basic. If you want more options, you should use the official Infinispan Spring Boot starter instead. See Infinispan’s documentation for more details. |
Couchbase
If the Couchbase Java client and the couchbase-spring-cache
implementation are available and Couchbase is configured, a
CouchbaseCacheManager
is auto-configured. It is also possible to create additional
caches on startup by setting the spring.cache.cache-names
property. These caches
operate on the Bucket
that was auto-configured. You can also create additional caches
on another Bucket
by using the customizer. Assume you need two caches (cache1
and
cache2
) on the "main" Bucket
and one (cache3
) cache with a custom time to live of 2
seconds on the “another” Bucket
. You can create the first two caches through
configuration, as follows:
spring.cache.cache-names=cache1,cache2
Then you can define a @Configuration
class to configure the extra Bucket
and the
cache3
cache, as follows:
@Configuration(proxyBeanMethods = false)
public class CouchbaseCacheConfiguration {
private final Cluster cluster;
public CouchbaseCacheConfiguration(Cluster cluster) {
this.cluster = cluster;
}
@Bean
public Bucket anotherBucket() {
return this.cluster.openBucket("another", "secret");
}
@Bean
public CacheManagerCustomizer<CouchbaseCacheManager> cacheManagerCustomizer() {
return c -> {
c.prepareCache("cache3", CacheBuilder.newInstance(anotherBucket())
.withExpiration(2));
};
}
}
This sample configuration reuses the Cluster
that was created through
auto-configuration.
Redis
If Redis is available and configured, a RedisCacheManager
is
auto-configured. It is possible to create additional caches on startup by setting the
spring.cache.cache-names
property and cache defaults can be configured by using
spring.cache.redis.*
properties. For instance, the following configuration creates
cache1
and cache2
caches with a time to live of 10 minutes:
spring.cache.cache-names=cache1,cache2
spring.cache.redis.time-to-live=600000
By default, a key prefix is added so that, if two separate caches use the same
key, Redis does not have overlapping keys and cannot return invalid values. We strongly
recommend keeping this setting enabled if you create your own |
You can take full control of the configuration by adding a RedisCacheConfiguration
@Bean of your own. This can be useful if you’re looking for customizing the
serialization strategy.
|
Caffeine
Caffeine is a Java 8 rewrite of Guava’s cache that
supersedes support for Guava. If Caffeine is present, a CaffeineCacheManager
(provided
by the spring-boot-starter-cache
“Starter”) is auto-configured. Caches can be created
on startup by setting the spring.cache.cache-names
property and can be customized by one
of the following (in the indicated order):
-
A cache spec defined by
spring.cache.caffeine.spec
-
A
com.github.benmanes.caffeine.cache.CaffeineSpec
bean is defined -
A
com.github.benmanes.caffeine.cache.Caffeine
bean is defined
For instance, the following configuration creates cache1
and cache2
caches with a
maximum size of 500 and a time to live of 10 minutes
spring.cache.cache-names=cache1,cache2
spring.cache.caffeine.spec=maximumSize=500,expireAfterAccess=600s
If a com.github.benmanes.caffeine.cache.CacheLoader
bean is defined, it is
automatically associated to the CaffeineCacheManager
. Since the CacheLoader
is going
to be associated with all caches managed by the cache manager, it must be defined as
CacheLoader<Object, Object>
. The auto-configuration ignores any other generic type.
Simple
If none of the other providers can be found, a simple implementation using a
ConcurrentHashMap
as the cache store is configured. This is the default if no caching
library is present in your application. By default, caches are created as needed, but you
can restrict the list of available caches by setting the cache-names
property. For
instance, if you want only cache1
and cache2
caches, set the cache-names
property
as follows:
spring.cache.cache-names=cache1,cache2
If you do so and your application uses a cache not listed, then it fails at runtime when the cache is needed, but not on startup. This is similar to the way the "real" cache providers behave if you use an undeclared cache.
4.13. Messaging
The Spring Framework provides extensive support for integrating with messaging systems,
from simplified use of the JMS API using JmsTemplate
to a complete infrastructure to
receive messages asynchronously. Spring AMQP provides a similar feature set for the
Advanced Message Queuing Protocol. Spring Boot also provides auto-configuration
options for RabbitTemplate
and RabbitMQ. Spring WebSocket natively includes support for
STOMP messaging, and Spring Boot has support for that through starters and a small amount
of auto-configuration. Spring Boot also has support for Apache Kafka.
4.13.1. JMS
The javax.jms.ConnectionFactory
interface provides a standard method of creating a
javax.jms.Connection
for interacting with a JMS broker. Although Spring needs a
ConnectionFactory
to work with JMS, you generally need not use it directly yourself and
can instead rely on higher level messaging abstractions. (See the
relevant section of the Spring Framework
reference documentation for details.) Spring Boot also auto-configures the necessary
infrastructure to send and receive messages.
ActiveMQ Support
When ActiveMQ is available on the classpath, Spring Boot can
also configure a ConnectionFactory
. If the broker is present, an embedded broker is
automatically started and configured (provided no broker URL is specified through
configuration).
If you use spring-boot-starter-activemq , the necessary dependencies to connect or
embed an ActiveMQ instance are provided, as is the Spring infrastructure to integrate with
JMS.
|
ActiveMQ configuration is controlled by external configuration properties in
spring.activemq.*
. For example, you might declare the following section in
application.properties
:
spring.activemq.broker-url=tcp://192.168.1.210:9876
spring.activemq.user=admin
spring.activemq.password=secret
By default, a CachingConnectionFactory
wraps the native ConnectionFactory
with
sensible settings that you can control by external configuration properties in
spring.jms.*
:
spring.jms.cache.session-cache-size=5
If you’d rather use native pooling, you can do so by adding a dependency to
org.messaginghub:pooled-jms
and configuring the JmsPoolConnectionFactory
accordingly,
as shown in the following example:
spring.activemq.pool.enabled=true
spring.activemq.pool.max-connections=50
See
ActiveMQProperties
for more of the supported options. You can also register an arbitrary number of beans
that implement ActiveMQConnectionFactoryCustomizer for more advanced customizations.
|
By default, ActiveMQ creates a destination if it does not yet exist so that destinations are resolved against their provided names.
Artemis Support
Spring Boot can auto-configure a ConnectionFactory
when it detects that
Artemis is available on the classpath. If the broker
is present, an embedded broker is automatically started and configured (unless the mode
property has been explicitly set). The supported modes are embedded
(to make explicit
that an embedded broker is required and that an error should occur if the broker is not
available on the classpath) and native
(to connect to a broker using the netty
transport protocol). When the latter is configured, Spring Boot configures a
ConnectionFactory
that connects to a broker running on the local machine with the
default settings.
If you use spring-boot-starter-artemis , the necessary dependencies to
connect to an existing Artemis instance are provided, as well as the Spring
infrastructure to integrate with JMS. Adding org.apache.activemq:artemis-jms-server to
your application lets you use embedded mode.
|
Artemis configuration is controlled by external configuration properties in
spring.artemis.*
. For example, you might declare the following section in
application.properties
:
spring.artemis.mode=native
spring.artemis.host=192.168.1.210
spring.artemis.port=9876
spring.artemis.user=admin
spring.artemis.password=secret
When embedding the broker, you can choose if you want to enable persistence and list the
destinations that should be made available. These can be specified as a comma-separated
list to create them with the default options, or you can define bean(s) of type
org.apache.activemq.artemis.jms.server.config.JMSQueueConfiguration
or
org.apache.activemq.artemis.jms.server.config.TopicConfiguration
, for advanced queue
and topic configurations, respectively.
By default, a CachingConnectionFactory
wraps the native ConnectionFactory
with
sensible settings that you can control by external configuration properties in
spring.jms.*
:
spring.jms.cache.session-cache-size=5
If you’d rather use native pooling, you can do so by adding a dependency to
org.messaginghub:pooled-jms
and configuring the JmsPoolConnectionFactory
accordingly,
as shown in the following example:
spring.artemis.pool.enabled=true
spring.artemis.pool.max-connections=50
See
ArtemisProperties
for more supported options.
No JNDI lookup is involved, and destinations are resolved against their names, using
either the name
attribute in the Artemis configuration or the names provided through
configuration.
Using a JNDI ConnectionFactory
If you are running your application in an application server, Spring Boot tries to
locate a JMS ConnectionFactory
by using JNDI. By default, the java:/JmsXA
and
java:/XAConnectionFactory
location are checked. You can use the spring.jms.jndi-name
property if you need to specify an alternative location, as shown in the following
example:
spring.jms.jndi-name=java:/MyConnectionFactory
Sending a Message
Spring’s JmsTemplate
is auto-configured, and you can autowire it directly into your own
beans, as shown in the following example:
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.jms.core.JmsTemplate;
import org.springframework.stereotype.Component;
@Component
public class MyBean {
private final JmsTemplate jmsTemplate;
@Autowired
public MyBean(JmsTemplate jmsTemplate) {
this.jmsTemplate = jmsTemplate;
}
// ...
}
JmsMessagingTemplate can
be injected in a similar manner. If a DestinationResolver or a MessageConverter bean
is defined, it is associated automatically to the auto-configured JmsTemplate .
|
Receiving a Message
When the JMS infrastructure is present, any bean can be annotated with @JmsListener
to
create a listener endpoint. If no JmsListenerContainerFactory
has been defined, a
default one is configured automatically. If a DestinationResolver
or a
MessageConverter
beans is defined, it is associated automatically to the default
factory.
By default, the default factory is transactional. If you run in an infrastructure where a
JtaTransactionManager
is present, it is associated to the listener container by default.
If not, the sessionTransacted
flag is enabled. In that latter scenario, you can
associate your local data store transaction to the processing of an incoming message by
adding @Transactional
on your listener method (or a delegate thereof). This ensures that
the incoming message is acknowledged, once the local transaction has completed. This also
includes sending response messages that have been performed on the same JMS session.
The following component creates a listener endpoint on the someQueue
destination:
@Component
public class MyBean {
@JmsListener(destination = "someQueue")
public void processMessage(String content) {
// ...
}
}
See the Javadoc of @EnableJms
for more details.
|
If you need to create more JmsListenerContainerFactory
instances or if you want to
override the default, Spring Boot provides a
DefaultJmsListenerContainerFactoryConfigurer
that you can use to initialize a
DefaultJmsListenerContainerFactory
with the same settings as the one that is
auto-configured.
For instance, the following example exposes another factory that uses a specific
MessageConverter
:
@Configuration(proxyBeanMethods = false)
static class JmsConfiguration {
@Bean
public DefaultJmsListenerContainerFactory myFactory(
DefaultJmsListenerContainerFactoryConfigurer configurer) {
DefaultJmsListenerContainerFactory factory =
new DefaultJmsListenerContainerFactory();
configurer.configure(factory, connectionFactory());
factory.setMessageConverter(myMessageConverter());
return factory;
}
}
Then you can use the factory in any @JmsListener
-annotated method as follows:
@Component
public class MyBean {
@JmsListener(destination = "someQueue", containerFactory="myFactory")
public void processMessage(String content) {
// ...
}
}
4.13.2. AMQP
The Advanced Message Queuing Protocol (AMQP) is a platform-neutral, wire-level protocol
for message-oriented middleware. The Spring AMQP project applies core Spring concepts to
the development of AMQP-based messaging solutions. Spring Boot offers several conveniences
for working with AMQP through RabbitMQ, including the spring-boot-starter-amqp
“Starter”.
RabbitMQ support
RabbitMQ is a lightweight, reliable, scalable, and portable
message broker based on the AMQP protocol. Spring uses RabbitMQ
to communicate through
the AMQP protocol.
RabbitMQ configuration is controlled by external configuration properties in
spring.rabbitmq.*
. For example, you might declare the following section in
application.properties
:
spring.rabbitmq.host=localhost
spring.rabbitmq.port=5672
spring.rabbitmq.username=admin
spring.rabbitmq.password=secret
If a ConnectionNameStrategy
bean exists in the context, it will be automatically used to
name connections created by the auto-configured ConnectionFactory
. See
RabbitProperties
for more
of the supported options.
See Understanding AMQP, the protocol used by RabbitMQ for more details. |
Sending a Message
Spring’s AmqpTemplate
and AmqpAdmin
are auto-configured, and you can autowire them
directly into your own beans, as shown in the following example:
import org.springframework.amqp.core.AmqpAdmin;
import org.springframework.amqp.core.AmqpTemplate;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Component;
@Component
public class MyBean {
private final AmqpAdmin amqpAdmin;
private final AmqpTemplate amqpTemplate;
@Autowired
public MyBean(AmqpAdmin amqpAdmin, AmqpTemplate amqpTemplate) {
this.amqpAdmin = amqpAdmin;
this.amqpTemplate = amqpTemplate;
}
// ...
}
RabbitMessagingTemplate
can be injected in a similar manner. If a MessageConverter bean is defined, it is
associated automatically to the auto-configured AmqpTemplate .
|
If necessary, any org.springframework.amqp.core.Queue
that is defined as a bean is
automatically used to declare a corresponding queue on the RabbitMQ instance.
To retry operations, you can enable retries on the AmqpTemplate
(for example, in the
event that the broker connection is lost):
spring.rabbitmq.template.retry.enabled=true
spring.rabbitmq.template.retry.initial-interval=2s
Retries are disabled by default. You can also customize the RetryTemplate
programmatically by declaring a RabbitRetryTemplateCustomizer
bean.
Receiving a Message
When the Rabbit infrastructure is present, any bean can be annotated with
@RabbitListener
to create a listener endpoint. If no RabbitListenerContainerFactory
has been defined, a default SimpleRabbitListenerContainerFactory
is automatically
configured and you can switch to a direct container using the
spring.rabbitmq.listener.type
property. If a MessageConverter
or a MessageRecoverer
bean is defined, it is automatically associated with the default factory.
The following sample component creates a listener endpoint on the someQueue
queue:
@Component
public class MyBean {
@RabbitListener(queues = "someQueue")
public void processMessage(String content) {
// ...
}
}
See the Javadoc of
@EnableRabbit for more details.
|
If you need to create more RabbitListenerContainerFactory
instances or if you want to
override the default, Spring Boot provides a
SimpleRabbitListenerContainerFactoryConfigurer
and a
DirectRabbitListenerContainerFactoryConfigurer
that you can use to initialize a
SimpleRabbitListenerContainerFactory
and a DirectRabbitListenerContainerFactory
with
the same settings as the factories used by the auto-configuration.
It does not matter which container type you chose. Those two beans are exposed by the auto-configuration. |
For instance, the following configuration class exposes another factory that uses a
specific MessageConverter
:
@Configuration(proxyBeanMethods = false)
static class RabbitConfiguration {
@Bean
public SimpleRabbitListenerContainerFactory myFactory(
SimpleRabbitListenerContainerFactoryConfigurer configurer) {
SimpleRabbitListenerContainerFactory factory =
new SimpleRabbitListenerContainerFactory();
configurer.configure(factory, connectionFactory);
factory.setMessageConverter(myMessageConverter());
return factory;
}
}
Then you can use the factory in any @RabbitListener
-annotated method, as follows:
@Component
public class MyBean {
@RabbitListener(queues = "someQueue", containerFactory="myFactory")
public void processMessage(String content) {
// ...
}
}
You can enable retries to handle situations where your listener throws an exception. By
default, RejectAndDontRequeueRecoverer
is used, but you can define a MessageRecoverer
of your own. When retries are exhausted, the message is rejected and either dropped or
routed to a dead-letter exchange if the broker is configured to do so. By default,
retries are disabled. You can also customize the RetryTemplate
programmatically by
declaring a RabbitRetryTemplateCustomizer
bean.
By default, if retries are disabled and the listener throws an exception, the
delivery is retried indefinitely. You can modify this behavior in two ways: Set the
defaultRequeueRejected property to false so that zero re-deliveries are attempted or
throw an AmqpRejectAndDontRequeueException to signal the message should be rejected.
The latter is the mechanism used when retries are enabled and the maximum number of
delivery attempts is reached.
|
4.13.3. Apache Kafka Support
Apache Kafka is supported by providing auto-configuration of
the spring-kafka
project.
Kafka configuration is controlled by external configuration properties in
spring.kafka.*
. For example, you might declare the following section in
application.properties
:
spring.kafka.bootstrap-servers=localhost:9092
spring.kafka.consumer.group-id=myGroup
To create a topic on startup, add a bean of type NewTopic . If the topic already
exists, the bean is ignored.
|
See KafkaProperties
for more supported options.
Sending a Message
Spring’s KafkaTemplate
is auto-configured, and you can autowire it directly in your own
beans, as shown in the following example:
@Component
public class MyBean {
private final KafkaTemplate kafkaTemplate;
@Autowired
public MyBean(KafkaTemplate kafkaTemplate) {
this.kafkaTemplate = kafkaTemplate;
}
// ...
}
If the property spring.kafka.producer.transaction-id-prefix is defined, a
KafkaTransactionManager is automatically configured. Also, if a RecordMessageConverter
bean is defined, it is automatically associated to the auto-configured KafkaTemplate .
|
Receiving a Message
When the Apache Kafka infrastructure is present, any bean can be annotated with
@KafkaListener
to create a listener endpoint. If no KafkaListenerContainerFactory
has
been defined, a default one is automatically configured with keys defined in
spring.kafka.listener.*
.
The following component creates a listener endpoint on the someTopic
topic:
@Component
public class MyBean {
@KafkaListener(topics = "someTopic")
public void processMessage(String content) {
// ...
}
}
If a KafkaTransactionManager
bean is defined, it is automatically associated to the
container factory. Similarly, if a ErrorHandler
, AfterRollbackProcessor
or
ConsumerAwareRebalanceListener
bean is defined, it is automatically associated to the
default factory.
Depending on the listener type, a RecordMessageConverter
or BatchMessageConverter
bean
is associated to the default factory. If only a RecordMessageConverter
bean is present
for a batch listener, it is wrapped in a BatchMessageConverter
.
A custom ChainedKafkaTransactionManager must be marked @Primary as it usually
references the auto-configured KafkaTransactionManager bean.
|
Kafka Streams
Spring for Apache Kafka provides a factory bean to create a StreamsBuilder
object and
manage the lifecycle of its streams. Spring Boot auto-configures the required
KafkaStreamsConfiguration
bean as long as kafka-streams
is on the classpath and Kafka
Streams is enabled via the @EnableKafkaStreams
annotation.
Enabling Kafka Streams means that the application id and bootstrap servers must be set.
The former can be configured using spring.kafka.streams.application-id
, defaulting to
spring.application.name
if not set. The latter can be set globally or
specifically overridden just for streams.
Several additional properties are available using dedicated properties; other arbitrary
Kafka properties can be set using the spring.kafka.streams.properties
namespace. See
also Additional Kafka Properties for more information.
To use the factory bean, simply wire StreamsBuilder
into your @Bean
as shown in the
following example:
@Configuration(proxyBeanMethods = false)
@EnableKafkaStreams
public static class KafkaStreamsExampleConfiguration {
@Bean
public KStream<Integer, String> kStream(StreamsBuilder streamsBuilder) {
KStream<Integer, String> stream = streamsBuilder.stream("ks1In");
stream.map((k, v) -> new KeyValue<>(k, v.toUpperCase())).to("ks1Out",
Produced.with(Serdes.Integer(), new JsonSerde<>()));
return stream;
}
}
By default, the streams managed by the StreamBuilder
object it creates are started
automatically. You can customize this behaviour using the
spring.kafka.streams.auto-startup
property.
Additional Kafka Properties
The properties supported by auto configuration are shown in Common application properties. Note that, for the most part, these properties (hyphenated or camelCase) map directly to the Apache Kafka dotted properties. Refer to the Apache Kafka documentation for details.
The first few of these properties apply to all components (producers, consumers, admins, and streams) but can be specified at the component level if you wish to use different values. Apache Kafka designates properties with an importance of HIGH, MEDIUM, or LOW. Spring Boot auto-configuration supports all HIGH importance properties, some selected MEDIUM and LOW properties, and any properties that do not have a default value.
Only a subset of the properties supported by Kafka are available directly through the
KafkaProperties
class. If you wish to configure the producer or consumer with additional
properties that are not directly supported, use the following properties:
spring.kafka.properties.prop.one=first
spring.kafka.admin.properties.prop.two=second
spring.kafka.consumer.properties.prop.three=third
spring.kafka.producer.properties.prop.four=fourth
spring.kafka.streams.properties.prop.five=fifth
This sets the common prop.one
Kafka property to first
(applies to producers,
consumers and admins), the prop.two
admin property to second
, the prop.three
consumer property to third
, the prop.four
producer property to fourth
and the
prop.five
streams property to fifth
.
You can also configure the Spring Kafka JsonDeserializer
as follows:
spring.kafka.consumer.value-deserializer=org.springframework.kafka.support.serializer.JsonDeserializer
spring.kafka.consumer.properties.spring.json.value.default.type=com.example.Invoice
spring.kafka.consumer.properties.spring.json.trusted.packages=com.example,org.acme
Similarly, you can disable the JsonSerializer
default behavior of sending type
information in headers:
spring.kafka.producer.value-serializer=org.springframework.kafka.support.serializer.JsonSerializer
spring.kafka.producer.properties.spring.json.add.type.headers=false
Properties set in this way override any configuration item that Spring Boot explicitly supports. |
Testing with Embedded Kafka
Spring for Apache Kafka provides a convenient way to test projects with an embedded Apache Kafka
broker. To use this feature, annotate a test class with @EmbeddedKafka
from the spring-kafka-test
module. For more information, please see the Spring for Apache Kafka
reference manual.
To make Spring Boot auto-configuration work with the aforementioned embedded Apache Kafka broker, you need
to remap a system property for embedded broker addresses (populated by the EmbeddedKafkaBroker
)
into the Spring Boot configuration property for Apache Kafka. There are several ways to do that:
-
Provide a system property to map embedded broker addresses into
spring.kafka.bootstrap-servers
in the test class:
static {
System.setProperty(EmbeddedKafkaBroker.BROKER_LIST_PROPERTY, "spring.kafka.bootstrap-servers");
}
-
Configure a property name on the
@EmbeddedKafka
annotation:
@EmbeddedKafka(topics = "someTopic",
bootstrapServersProperty = "spring.kafka.bootstrap-servers")
-
Use a placeholder in configuration properties:
spring.kafka.bootstrap-servers=${spring.embedded.kafka.brokers}
4.14. Calling REST Services with RestTemplate
If you need to call remote REST services from your application, you can use the Spring
Framework’s RestTemplate
class. Since
RestTemplate
instances often need to be customized before being used, Spring Boot does
not provide any single auto-configured RestTemplate
bean. It does, however,
auto-configure a RestTemplateBuilder
, which can be used to create RestTemplate
instances when needed. The auto-configured RestTemplateBuilder
ensures that sensible
HttpMessageConverters
are applied to RestTemplate
instances.
The following code shows a typical example:
@Service
public class MyService {
private final RestTemplate restTemplate;
public MyService(RestTemplateBuilder restTemplateBuilder) {
this.restTemplate = restTemplateBuilder.build();
}
public Details someRestCall(String name) {
return this.restTemplate.getForObject("/{name}/details", Details.class, name);
}
}
RestTemplateBuilder includes a number of useful methods that can be used to
quickly configure a RestTemplate . For example, to add BASIC auth support, you can use
builder.basicAuthentication("user", "password").build() .
|
4.14.1. RestTemplate Customization
There are three main approaches to RestTemplate
customization, depending on how broadly
you want the customizations to apply.
To make the scope of any customizations as narrow as possible, inject the auto-configured
RestTemplateBuilder
and then call its methods as required. Each method call returns a
new RestTemplateBuilder
instance, so the customizations only affect this use of the
builder.
To make an application-wide, additive customization, use a RestTemplateCustomizer
bean.
All such beans are automatically registered with the auto-configured RestTemplateBuilder
and are applied to any templates that are built with it.
The following example shows a customizer that configures the use of a proxy for all hosts
except 192.168.0.5
:
static class ProxyCustomizer implements RestTemplateCustomizer {
@Override
public void customize(RestTemplate restTemplate) {
HttpHost proxy = new HttpHost("proxy.example.com");
HttpClient httpClient = HttpClientBuilder.create().setRoutePlanner(new DefaultProxyRoutePlanner(proxy) {
@Override
public HttpHost determineProxy(HttpHost target, HttpRequest request, HttpContext context)
throws HttpException {
if (target.getHostName().equals("192.168.0.5")) {
return null;
}
return super.determineProxy(target, request, context);
}
}).build();
restTemplate.setRequestFactory(new HttpComponentsClientHttpRequestFactory(httpClient));
}
}
Finally, the most extreme (and rarely used) option is to create your own
RestTemplateBuilder
bean. Doing so switches off the auto-configuration of a
RestTemplateBuilder
and prevents any RestTemplateCustomizer
beans from being used.
4.15. Calling REST Services with WebClient
If you have Spring WebFlux on your classpath, you can also choose to use WebClient
to
call remote REST services. Compared to RestTemplate
, this client has a more functional
feel and is fully reactive. You can learn more about the WebClient
in the dedicated
section in the Spring Framework docs.
Spring Boot creates and pre-configures a WebClient.Builder
for you; it is strongly
advised to inject it in your components and use it to create WebClient
instances.
Spring Boot is configuring that builder to share HTTP resources, reflect codecs
setup in the same fashion as the server ones (see
WebFlux HTTP codecs auto-configuration), and more.
The following code shows a typical example:
@Service
public class MyService {
private final WebClient webClient;
public MyService(WebClient.Builder webClientBuilder) {
this.webClient = webClientBuilder.baseUrl("https://example.org").build();
}
public Mono<Details> someRestCall(String name) {
return this.webClient.get().uri("/{name}/details", name)
.retrieve().bodyToMono(Details.class);
}
}
4.15.1. WebClient Runtime
Spring Boot will auto-detect which ClientHttpConnector
to use to drive WebClient
,
depending on the libraries available on the application classpath. For now, Reactor
Netty and Jetty RS client are supported.
The spring-boot-starter-webflux
starter depends on io.projectreactor.netty:reactor-netty
by default, which brings both server and client implementations. If you choose to use Jetty
as a reactive server instead, you should add a dependency on the Jetty Reactive HTTP
client library, org.eclipse.jetty:jetty-reactive-httpclient
. Using the same technology
for server and client has it advantages, as it will automatically share HTTP resources
between client and server.
Developers can override the resource configuration for Jetty and Reactor Netty by providing
a custom ReactorResourceFactory
or JettyResourceFactory
bean - this will be applied to
both clients and servers.
If you wish to override that choice for the client, you can define your own
ClientHttpConnector
bean and have full control over the client configuration.
You can learn more about the
WebClient
configuration
options in the Spring Framework reference documentation.
4.15.2. WebClient Customization
There are three main approaches to WebClient
customization, depending on how broadly you
want the customizations to apply.
To make the scope of any customizations as narrow as possible, inject the auto-configured
WebClient.Builder
and then call its methods as required. WebClient.Builder
instances
are stateful: Any change on the builder is reflected in all clients subsequently created
with it. If you want to create several clients with the same builder, you can also
consider cloning the builder with WebClient.Builder other = builder.clone();
.
To make an application-wide, additive customization to all WebClient.Builder
instances,
you can declare WebClientCustomizer
beans and change the WebClient.Builder
locally at
the point of injection.
Finally, you can fall back to the original API and use WebClient.create()
. In that case,
no auto-configuration or WebClientCustomizer
is applied.
4.16. Validation
The method validation feature supported by Bean Validation 1.1 is automatically enabled
as long as a JSR-303 implementation (such as Hibernate validator) is on the classpath.
This lets bean methods be annotated with javax.validation
constraints on their
parameters and/or on their return value. Target classes with such annotated methods need
to be annotated with the @Validated
annotation at the type level for their methods to
be searched for inline constraint annotations.
For instance, the following service triggers the validation of the first argument, making sure its size is between 8 and 10:
@Service
@Validated
public class MyBean {
public Archive findByCodeAndAuthor(@Size(min = 8, max = 10) String code,
Author author) {
...
}
}
4.17. Sending Email
The Spring Framework provides an easy abstraction for sending email by using the
JavaMailSender
interface, and Spring Boot provides auto-configuration for it as well as
a starter module.
See the reference documentation for a
detailed explanation of how you can use JavaMailSender .
|
If spring.mail.host
and the relevant libraries (as defined by
spring-boot-starter-mail
) are available, a default JavaMailSender
is created if none
exists. The sender can be further customized by configuration items from the
spring.mail
namespace. See
MailProperties
for more
details.
In particular, certain default timeout values are infinite, and you may want to change that to avoid having a thread blocked by an unresponsive mail server, as shown in the following example:
spring.mail.properties.mail.smtp.connectiontimeout=5000
spring.mail.properties.mail.smtp.timeout=3000
spring.mail.properties.mail.smtp.writetimeout=5000
It is also possible to configure a JavaMailSender
with an existing Session
from JNDI:
spring.mail.jndi-name=mail/Session
When a jndi-name
is set, it takes precedence over all other Session-related settings.
4.18. Distributed Transactions with JTA
Spring Boot supports distributed JTA transactions across multiple XA resources by using either an Atomikos or Bitronix embedded transaction manager. JTA transactions are also supported when deploying to a suitable Java EE Application Server.
When a JTA environment is detected, Spring’s JtaTransactionManager
is used to manage
transactions. Auto-configured JMS, DataSource, and JPA beans are upgraded to support XA
transactions. You can use standard Spring idioms, such as @Transactional
, to participate
in a distributed transaction. If you are within a JTA environment and still want to use
local transactions, you can set the spring.jta.enabled
property to false
to disable
the JTA auto-configuration.
4.18.1. Using an Atomikos Transaction Manager
Atomikos is a popular open source transaction manager which can
be embedded into your Spring Boot application. You can use the
spring-boot-starter-jta-atomikos
Starter to pull in the appropriate Atomikos libraries.
Spring Boot auto-configures Atomikos and ensures that appropriate depends-on
settings
are applied to your Spring beans for correct startup and shutdown ordering.
By default, Atomikos transaction logs are written to a transaction-logs
directory in
your application’s home directory (the directory in which your application jar file
resides). You can customize the location of this directory by setting a
spring.jta.log-dir
property in your application.properties
file. Properties starting
with spring.jta.atomikos.properties
can also be used to customize the Atomikos
UserTransactionServiceImp
. See the
AtomikosProperties
Javadoc
for complete details.
To ensure that multiple transaction managers can safely coordinate the same
resource managers, each Atomikos instance must be configured with a unique ID. By default,
this ID is the IP address of the machine on which Atomikos is running. To ensure
uniqueness in production, you should configure the spring.jta.transaction-manager-id
property with a different value for each instance of your application.
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4.18.2. Using a Bitronix Transaction Manager
Bitronix is a popular open-source JTA transaction
manager implementation. You can use the spring-boot-starter-jta-bitronix
starter to add
the appropriate Bitronix dependencies to your project. As with Atomikos, Spring Boot
automatically configures Bitronix and post-processes your beans to ensure that startup and
shutdown ordering is correct.
By default, Bitronix transaction log files (part1.btm
and part2.btm
) are written to
a transaction-logs
directory in your application home directory. You can customize the
location of this directory by setting the spring.jta.log-dir
property. Properties
starting with spring.jta.bitronix.properties
are also bound to the
bitronix.tm.Configuration
bean, allowing for complete customization. See the
Bitronix
documentation for details.
To ensure that multiple transaction managers can safely coordinate the same
resource managers, each Bitronix instance must be configured with a unique ID. By default,
this ID is the IP address of the machine on which Bitronix is running. To ensure
uniqueness in production, you should configure the spring.jta.transaction-manager-id
property with a different value for each instance of your application.
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4.18.3. Using a Java EE Managed Transaction Manager
If you package your Spring Boot application as a war
or ear
file and deploy it to a
Java EE application server, you can use your application server’s built-in transaction
manager. Spring Boot tries to auto-configure a transaction manager by looking at common
JNDI locations (java:comp/UserTransaction
, java:comp/TransactionManager
, and so on).
If you use a transaction service provided by your application server, you generally also
want to ensure that all resources are managed by the server and exposed over JNDI. Spring
Boot tries to auto-configure JMS by looking for a ConnectionFactory
at the JNDI path
(java:/JmsXA
or java:/XAConnectionFactory
), and you can use the
spring.datasource.jndi-name
property
to configure your DataSource
.
4.18.4. Mixing XA and Non-XA JMS Connections
When using JTA, the primary JMS ConnectionFactory
bean is XA-aware and participates
in distributed transactions. In some situations, you might want to process certain JMS
messages by using a non-XA ConnectionFactory
. For example, your JMS processing logic
might take longer than the XA timeout.
If you want to use a non-XA ConnectionFactory
, you can inject the
nonXaJmsConnectionFactory
bean rather than the @Primary
jmsConnectionFactory
bean.
For consistency, the jmsConnectionFactory
bean is also provided by using the bean alias
xaJmsConnectionFactory
.
The following example shows how to inject ConnectionFactory
instances:
// Inject the primary (XA aware) ConnectionFactory
@Autowired
private ConnectionFactory defaultConnectionFactory;
// Inject the XA aware ConnectionFactory (uses the alias and injects the same as above)
@Autowired
@Qualifier("xaJmsConnectionFactory")
private ConnectionFactory xaConnectionFactory;
// Inject the non-XA aware ConnectionFactory
@Autowired
@Qualifier("nonXaJmsConnectionFactory")
private ConnectionFactory nonXaConnectionFactory;
4.18.5. Supporting an Alternative Embedded Transaction Manager
The XAConnectionFactoryWrapper
and XADataSourceWrapper
interfaces
can be used to support alternative embedded transaction managers. The interfaces are
responsible for wrapping XAConnectionFactory
and XADataSource
beans and exposing them
as regular ConnectionFactory
and DataSource
beans, which transparently enroll in the
distributed transaction. DataSource and JMS auto-configuration use JTA variants, provided
you have a JtaTransactionManager
bean and appropriate XA wrapper beans registered
within your ApplicationContext
.
The BitronixXAConnectionFactoryWrapper and BitronixXADataSourceWrapper provide good examples of how to write XA wrappers.
4.19. Hazelcast
If Hazelcast is on the classpath and a suitable configuration is
found, Spring Boot auto-configures a HazelcastInstance
that you can inject in your
application.
If you define a com.hazelcast.config.Config
bean, Spring Boot uses that. If your
configuration defines an instance name, Spring Boot tries to locate an existing instance
rather than creating a new one.
You could also specify the Hazelcast configuration file to use through configuration, as shown in the following example:
spring.hazelcast.config=classpath:config/my-hazelcast.xml
Otherwise, Spring Boot tries to find the Hazelcast configuration from the default
locations: hazelcast.xml
in the working directory or at the root of the classpath, or
a .yaml
counterpart in the same locations. We also check if the hazelcast.config
system property is set. See the
Hazelcast documentation for
more details.
If hazelcast-client
is present on the classpath, Spring Boot first attempts to create a
client by checking the following configuration options:
-
The presence of a
com.hazelcast.client.config.ClientConfig
bean. -
A configuration file defined by the
spring.hazelcast.config
property. -
The presence of the
hazelcast.client.config
system property. -
A
hazelcast-client.xml
in the working directory or at the root of the classpath. -
A
hazelcast-client.yaml
in the working directory or at the root of the classpath.
Spring Boot also has
explicit caching support for Hazelcast. If
caching is enabled, the HazelcastInstance is automatically wrapped in a CacheManager
implementation.
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4.20. Quartz Scheduler
Spring Boot offers several conveniences for working with the
Quartz scheduler, including the
spring-boot-starter-quartz
“Starter”. If Quartz is available, a Scheduler
is
auto-configured (through the SchedulerFactoryBean
abstraction).
Beans of the following types are automatically picked up and associated with the
Scheduler
:
-
JobDetail
: defines a particular Job.JobDetail
instances can be built with theJobBuilder
API. -
Calendar
. -
Trigger
: defines when a particular job is triggered.
By default, an in-memory JobStore
is used. However, it is possible to configure a
JDBC-based store if a DataSource
bean is available in your application and if the
spring.quartz.job-store-type
property is configured accordingly, as shown in the
following example:
spring.quartz.job-store-type=jdbc
When the JDBC store is used, the schema can be initialized on startup, as shown in the following example:
spring.quartz.jdbc.initialize-schema=always
By default, the database is detected and initialized by using the standard scripts
provided with the Quartz library. These scripts drop existing tables, deleting all triggers
on every restart. It is also possible to provide a custom script by setting the
spring.quartz.jdbc.schema property.
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To have Quartz use a DataSource
other than the application’s main DataSource
, declare
a DataSource
bean, annotating its @Bean
method with @QuartzDataSource
. Doing so
ensures that the Quartz-specific DataSource
is used by both the SchedulerFactoryBean
and for schema initialization.
By default, jobs created by configuration will not overwrite already registered jobs that
have been read from a persistent job store. To enable overwriting existing job definitions
set the spring.quartz.overwrite-existing-jobs
property.
Quartz Scheduler configuration can be customized using spring.quartz
properties and
SchedulerFactoryBeanCustomizer
beans, which allow programmatic SchedulerFactoryBean
customization. Advanced Quartz configuration properties can be customized using
spring.quartz.properties.*
.
In particular, an Executor bean is not associated with the scheduler as Quartz
offers a way to configure the scheduler via spring.quartz.properties . If you need
to customize the task executor, consider implementing SchedulerFactoryBeanCustomizer .
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Jobs can define setters to inject data map properties. Regular beans can also be injected in a similar manner, as shown in the following example:
public class SampleJob extends QuartzJobBean {
private MyService myService;
private String name;
// Inject "MyService" bean
public void setMyService(MyService myService) { ... }
// Inject the "name" job data property
public void setName(String name) { ... }
@Override
protected void executeInternal(JobExecutionContext context)
throws JobExecutionException {
...
}
}
4.21. Task Execution and Scheduling
In the absence of an Executor
bean in the context, Spring Boot auto-configures a
ThreadPoolTaskExecutor
with sensible defaults that can be automatically associated to
asynchronous task execution (@EnableAsync
) and Spring MVC asynchronous request
processing.
If you have defined a custom The auto-configured |
The thread pool uses 8 core threads that can grow and shrink according to the load. Those
default settings can be fine-tuned using the spring.task.execution
namespace as shown in
the following example:
spring.task.execution.pool.max-threads=16
spring.task.execution.pool.queue-capacity=100
spring.task.execution.pool.keep-alive=10s
This changes the thread pool to use a bounded queue so that when the queue is full (100 tasks), the thread pool increases to maximum 16 threads. Shrinking of the pool is more aggressive as threads are reclaimed when they are idle for 10 seconds (rather than 60 seconds by default).
A ThreadPoolTaskScheduler
can also be auto-configured if need to be associated to
scheduled task execution (@EnableScheduling
). The thread pool uses one thread by default
and those settings can be fine-tuned using the spring.task.scheduling
namespace.
Both a TaskExecutorBuilder
bean and a TaskSchedulerBuilder
bean are made available in
the context if a custom executor or scheduler needs to be created.
4.22. Spring Integration
Spring Boot offers several conveniences for working with Spring
Integration, including the spring-boot-starter-integration
“Starter”. Spring
Integration provides abstractions over messaging and also other transports such as HTTP,
TCP, and others. If Spring Integration is available on your classpath, it is initialized
through the @EnableIntegration
annotation.
Spring Boot also configures some features that are triggered by the presence of additional
Spring Integration modules. If spring-integration-jmx
is also on the classpath,
message processing statistics are published over JMX . If spring-integration-jdbc
is
available, the default database schema can be created on startup, as shown in the
following line:
spring.integration.jdbc.initialize-schema=always
See the
IntegrationAutoConfiguration
and IntegrationProperties
classes for more details.
By default, if a Micrometer meterRegistry
bean is present, Spring Integration metrics
will be managed by Micrometer. If you wish to use legacy Spring Integration metrics, add
a DefaultMetricsFactory
bean to the application context.
4.23. Spring Session
Spring Boot provides Spring Session auto-configuration for a wide range of data stores. When building a Servlet web application, the following stores can be auto-configured:
-
JDBC
-
Redis
-
Hazelcast
-
MongoDB
When building a reactive web application, the following stores can be auto-configured:
-
Redis
-
MongoDB
If a single Spring Session module is present on the classpath, Spring Boot uses that store
implementation automatically. If you have more than one implementation, you must choose
the StoreType
that you wish
to use to store the sessions. For instance, to use JDBC as the back-end store, you can
configure your application as follows:
spring.session.store-type=jdbc
You can disable Spring Session by setting the store-type to none .
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Each store has specific additional settings. For instance, it is possible to customize the name of the table for the JDBC store, as shown in the following example:
spring.session.jdbc.table-name=SESSIONS
For setting the timeout of the session you can use the spring.session.timeout
property.
If that property is not set, the auto-configuration falls back to the value of
server.servlet.session.timeout
.
4.24. Monitoring and Management over JMX
Java Management Extensions (JMX) provide a standard mechanism to monitor and manage
applications. Spring Boot exposes the most suitable MBeanServer
as a bean with an ID of
mbeanServer
. Any of your beans that are annotated with Spring JMX annotations (
@ManagedResource
, @ManagedAttribute
, or @ManagedOperation
) are exposed to it.
If your platform provides a standard MBeanServer
, Spring Boot will use that and default
to the VM MBeanServer
if necessary. If all that fails, a new MBeanServer
will be
created.
See the
JmxAutoConfiguration
class for more details.
4.25. Testing
Spring Boot provides a number of utilities and annotations to help when testing your
application. Test support is provided by two modules: spring-boot-test
contains core
items, and spring-boot-test-autoconfigure
supports auto-configuration for tests.
Most developers use the spring-boot-starter-test
“Starter”, which imports both Spring
Boot test modules as well as JUnit Jupiter, AssertJ, Hamcrest, and a number of other
useful libraries.
The starter also brings the vintage engine so that you can run both JUnit 4 and JUnit 5 tests. If you have migrated your tests to JUnit 5, you should exclude JUnit 4 support, as shown in the following example:
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4.25.1. Test Scope Dependencies
The spring-boot-starter-test
“Starter” (in the test
scope
) contains
the following provided libraries:
-
JUnit 5 (including the vintage engine for backward compatibility with JUnit 4: The de-facto standard for unit testing Java applications.
-
Spring Test & Spring Boot Test: Utilities and integration test support for Spring Boot applications.
-
AssertJ: A fluent assertion library.
-
Hamcrest: A library of matcher objects (also known as constraints or predicates).
-
Mockito: A Java mocking framework.
-
JSONassert: An assertion library for JSON.
-
JsonPath: XPath for JSON.
We generally find these common libraries to be useful when writing tests. If these libraries do not suit your needs, you can add additional test dependencies of your own.
4.25.2. Testing Spring Applications
One of the major advantages of dependency injection is that it should make your code
easier to unit test. You can instantiate objects by using the new
operator without
even involving Spring. You can also use mock objects instead of real dependencies.
Often, you need to move beyond unit testing and start integration testing (with
a Spring ApplicationContext
). It is useful to be able to perform integration testing
without requiring deployment of your application or needing to connect to other
infrastructure.
The Spring Framework includes a dedicated test module for such integration testing. You
can declare a dependency directly to org.springframework:spring-test
or use the
spring-boot-starter-test
“Starter” to pull it in transitively.
If you have not used the spring-test
module before, you should start by reading the
relevant section of the Spring Framework
reference documentation.
4.25.3. Testing Spring Boot Applications
A Spring Boot application is a Spring ApplicationContext
, so nothing very special has
to be done to test it beyond what you would normally do with a vanilla Spring context.
External properties, logging, and other features of Spring Boot are installed in the
context by default only if you use SpringApplication to create it.
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Spring Boot provides a @SpringBootTest
annotation, which can be used as an alternative
to the standard spring-test
@ContextConfiguration
annotation when you need Spring
Boot features. The annotation works by
creating the
ApplicationContext
used in your tests through SpringApplication
. In addition to
@SpringBootTest
a number of other annotations are also provided for
testing more
specific slices of an application.
If you are using JUnit 4, don’t forget to also add @RunWith(SpringRunner.class) to
your test, otherwise the annotations will be ignored. If you are using JUnit 5, there’s no
need to add the equivalent @RunWith(SpringExtension.class) as @SpringBootTest and
the other @…Test annotations are already annotated with it.
|
By default, @SpringBootTest
will not start a server. You can use the webEnvironment
attribute of @SpringBootTest
to further refine how your tests run:
-
MOCK
(Default) : Loads a webApplicationContext
and provides a mock web environment. Embedded servers are not started when using this annotation. If a web environment is not available on your classpath, this mode transparently falls back to creating a regular non-webApplicationContext
. It can be used in conjunction with@AutoConfigureMockMvc
or@AutoConfigureWebTestClient
for mock-based testing of your web application. -
RANDOM_PORT
: Loads aWebServerApplicationContext
and provides a real web environment. Embedded servers are started and listen on a random port. -
DEFINED_PORT
: Loads aWebServerApplicationContext
and provides a real web environment. Embedded servers are started and listen on a defined port (from yourapplication.properties
) or on the default port of8080
. -
NONE
: Loads anApplicationContext
by usingSpringApplication
but does not provide any web environment (mock or otherwise).
If your test is @Transactional , it rolls back the transaction at the end of each
test method by default. However, as using this arrangement with either RANDOM_PORT or
DEFINED_PORT implicitly provides a real servlet environment, the HTTP client and server
run in separate threads and, thus, in separate transactions. Any transaction initiated on
the server does not roll back in this case.
|
@SpringBootTest with webEnvironment = WebEnvironment.RANDOM_PORT will also
start the management server on a separate random port if your application uses a different
port for the management server.
|
Detecting Web Application Type
If Spring MVC is available, a regular MVC-based application context is configured. If you have only Spring WebFlux, we’ll detect that and configure a WebFlux-based application context instead.
If both are present, Spring MVC takes precedence. If you want to test a reactive web
application in this scenario, you must set the spring.main.web-application-type
property:
@SpringBootTest(properties = "spring.main.web-application-type=reactive")
class MyWebFluxTests { ... }
Detecting Test Configuration
If you are familiar with the Spring Test Framework, you may be used to using
@ContextConfiguration(classes=…)
in order to specify which Spring @Configuration
to
load. Alternatively, you might have often used nested @Configuration
classes within
your test.
When testing Spring Boot applications, this is often not required. Spring Boot’s @*Test
annotations search for your primary configuration automatically whenever you do not
explicitly define one.
The search algorithm works up from the package that contains the test until it finds a
class annotated with @SpringBootApplication
or @SpringBootConfiguration
. As long as
you structured your code in a sensible way, your
main configuration is usually found.
If you use a test annotation to test a more specific slice of your application, you should avoid adding configuration settings that are specific to a particular area on the main method’s application class. The underlying component scan configuration of |
If you want to customize the primary configuration, you can use a nested
@TestConfiguration
class. Unlike a nested @Configuration
class, which would be used
instead of your application’s primary configuration, a nested @TestConfiguration
class
is used in addition to your application’s primary configuration.
Spring’s test framework caches application contexts between tests. Therefore, as long as your tests share the same configuration (no matter how it is discovered), the potentially time-consuming process of loading the context happens only once. |
Excluding Test Configuration
If your application uses component scanning (for example, if you use
@SpringBootApplication
or @ComponentScan
), you may find top-level configuration
classes that you created only for specific tests accidentally get picked up everywhere.
As we have seen
earlier, @TestConfiguration
can be used on an inner class of a test to customize the
primary configuration. When placed on a top-level class, @TestConfiguration
indicates
that classes in src/test/java
should not be picked up by scanning. You can then import
that class explicitly where it is required, as shown in the following example:
@SpringBootTest
@Import(MyTestsConfiguration.class)
class MyTests {
@Test
void exampleTest() {
...
}
}
If you directly use @ComponentScan (that is, not through
@SpringBootApplication ) you need to register the TypeExcludeFilter with it. See
the Javadoc for details.
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Using Application Arguments
If your application expects arguments, you can
have @SpringBootTest
inject them using the args
attribute.
@SpringBootTest(args = "--app.test=one")
class ApplicationArgumentsExampleTests {
@Test
void applicationArgumentsPopulated(@Autowired ApplicationArguments args) {
assertThat(args.getOptionNames()).containsOnly("app.test");
assertThat(args.getOptionValues("app.test")).containsOnly("one");
}
}
Testing with a mock environment
By default, @SpringBootTest
does not start the server. If you have web endpoints that
you want to test against this mock environment, you can additionally configure
MockMvc
as shown in the
following example:
import org.junit.jupiter.api.Test;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.autoconfigure.web.servlet.AutoConfigureMockMvc;
import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.test.web.servlet.MockMvc;
import static org.springframework.test.web.servlet.request.MockMvcRequestBuilders.get;
import static org.springframework.test.web.servlet.result.MockMvcResultMatchers.content;
import static org.springframework.test.web.servlet.result.MockMvcResultMatchers.status;
@SpringBootTest
@AutoConfigureMockMvc
class MockMvcExampleTests {
@Test
void exampleTest(@Autowired MockMvc mvc) throws Exception {
mvc.perform(get("/")).andExpect(status().isOk()).andExpect(content().string("Hello World"));
}
}
If you want to focus only on the web layer and not start a complete
ApplicationContext , consider
using
@WebMvcTest instead.
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Alternatively, you can configure a
WebTestClient
as shown in the
following example:
import org.junit.jupiter.api.Test;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.autoconfigure.web.reactive.AutoConfigureWebTestClient;
import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.test.web.reactive.server.WebTestClient;
@SpringBootTest
@AutoConfigureWebTestClient
class MockWebTestClientExampleTests {
@Test
void exampleTest(@Autowired WebTestClient webClient) {
webClient.get().uri("/").exchange().expectStatus().isOk().expectBody(String.class).isEqualTo("Hello World");
}
}
Testing with a running server
If you need to start a full running server, we recommend that you use random ports.
If you use @SpringBootTest(webEnvironment=WebEnvironment.RANDOM_PORT)
, an
available port is picked at random each time your test runs.
The @LocalServerPort
annotation can be used to
inject the actual port used into your test.
For convenience, tests that need to make REST calls to the started server can
additionally @Autowire
a
WebTestClient
, which resolves
relative links to the running server and comes with a dedicated API for verifying
responses, as shown in the following example:
import org.junit.jupiter.api.Test;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.boot.test.context.SpringBootTest.WebEnvironment;
import org.springframework.test.web.reactive.server.WebTestClient;
@SpringBootTest(webEnvironment = WebEnvironment.RANDOM_PORT)
class RandomPortWebTestClientExampleTests {
@Test
void exampleTest(@Autowired WebTestClient webClient) {
webClient.get().uri("/").exchange().expectStatus().isOk().expectBody(String.class).isEqualTo("Hello World");
}
}
This setup requires spring-webflux
on the classpath. If you can’t or won’t add webflux,
Spring Boot also provides a TestRestTemplate
facility:
import org.junit.jupiter.api.Test;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.boot.test.context.SpringBootTest.WebEnvironment;
import org.springframework.boot.test.web.client.TestRestTemplate;
import static org.assertj.core.api.Assertions.assertThat;
@SpringBootTest(webEnvironment = WebEnvironment.RANDOM_PORT)
class RandomPortTestRestTemplateExampleTests {
@Test
void exampleTest(@Autowired TestRestTemplate restTemplate) {
String body = restTemplate.getForObject("/", String.class);
assertThat(body).isEqualTo("Hello World");
}
}
Using JMX
As the test context framework caches context, JMX is disabled by default to prevent
identical components to register on the same domain. If such test needs access to an
MBeanServer
, consider marking it dirty as well:
@ExtendWith(SpringExtension.class)
@SpringBootTest(properties = "spring.jmx.enabled=true")
@DirtiesContext
class SampleJmxTests {
@Autowired
private MBeanServer mBeanServer;
@Test
void exampleTest() {
// ...
}
}
Mocking and Spying Beans
When running tests, it is sometimes necessary to mock certain components within your application context. For example, you may have a facade over some remote service that is unavailable during development. Mocking can also be useful when you want to simulate failures that might be hard to trigger in a real environment.
Spring Boot includes a @MockBean
annotation that can be used to define a Mockito mock
for a bean inside your ApplicationContext
. You can use the annotation to add new beans
or replace a single existing bean definition. The annotation can be used directly on test
classes, on fields within your test, or on @Configuration
classes and fields. When used
on a field, the instance of the created mock is also injected. Mock beans are
automatically reset after each test method.
If your test uses one of Spring Boot’s test annotations (such as
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The following example replaces an existing RemoteService
bean with a mock
implementation:
import org.junit.jupiter.api.Test;
import org.springframework.beans.factory.annotation.*;
import org.springframework.boot.test.context.*;
import org.springframework.boot.test.mock.mockito.*;
import static org.assertj.core.api.Assertions.*;
import static org.mockito.BDDMockito.*;
@SpringBootTest
class MyTests {
@MockBean
private RemoteService remoteService;
@Autowired
private Reverser reverser;
@Test
void exampleTest() {
// RemoteService has been injected into the reverser bean
given(this.remoteService.someCall()).willReturn("mock");
String reverse = reverser.reverseSomeCall();
assertThat(reverse).isEqualTo("kcom");
}
}
@MockBean cannot be used to mock the behavior of a bean that’s exercised during
application context refresh. By the time the test is executed, the application context refresh
has completed and it is too late to configure the mocked behavior. We recommend using a @Bean
method to create and configure the mock in this situation.
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Additionally, you can use @SpyBean
to wrap any existing bean with a Mockito spy
. See
the Javadoc for full details.
While Spring’s test framework caches application contexts between tests and reuses
a context for tests sharing the same configuration, the use of @MockBean or @SpyBean
influences the cache key, which will most likely increase the number of contexts.
|
If you are using @SpyBean to spy on a bean with @Cacheable methods that refer
to parameters by name, your application must be compiled with -parameters . This
ensures that the parameter names are available to the caching infrastructure once the
bean has been spied upon.
|
Auto-configured Tests
Spring Boot’s auto-configuration system works well for applications but can sometimes be a little too much for tests. It often helps to load only the parts of the configuration that are required to test a “slice” of your application. For example, you might want to test that Spring MVC controllers are mapping URLs correctly, and you do not want to involve database calls in those tests, or you might want to test JPA entities, and you are not interested in the web layer when those tests run.
The spring-boot-test-autoconfigure
module includes a number of annotations that can be
used to automatically configure such “slices”. Each of them works in a similar way,
providing a @…Test
annotation that loads the ApplicationContext
and one or
more @AutoConfigure…
annotations that can be used to customize auto-configuration
settings.
Each slice restricts component scan to appropriate components and loads a very
restricted set of auto-configuration classes. If you need to exclude one of them,
most @…Test annotations provide an excludeAutoConfiguration attribute.
Alternatively, you can use @ImportAutoConfiguration#exclude .
|
Including multiple “slices” by using several @…Test annotations in one test is
not supported. If you need multiple “slices”, pick one of the @…Test annotations
and include the @AutoConfigure… annotations of the other “slices” by hand.
|
It is also possible to use the @AutoConfigure… annotations with the standard
@SpringBootTest annotation. You can use this combination if you are not interested in
“slicing” your application but you want some of the auto-configured test beans.
|
Auto-configured JSON Tests
To test that object JSON serialization and deserialization is working as expected, you can
use the @JsonTest
annotation. @JsonTest
auto-configures the available supported JSON
mapper, which can be one of the following libraries:
-
Jackson
ObjectMapper
, any@JsonComponent
beans and any JacksonModule
s -
Gson
-
Jsonb
A list of the auto-configurations that are enabled by @JsonTest can be
found in the appendix.
|
If you need to configure elements of the auto-configuration, you can use the
@AutoConfigureJsonTesters
annotation.
Spring Boot includes AssertJ-based helpers that work with the JSONAssert and JsonPath
libraries to check that JSON appears as expected. The JacksonTester
, GsonTester
,
JsonbTester
, and BasicJsonTester
classes can be used for Jackson, Gson, Jsonb, and
Strings respectively. Any helper fields on the test class can be @Autowired
when using
@JsonTest
. The following example shows a test class for Jackson:
import org.junit.jupiter.api.Test;
import org.springframework.beans.factory.annotation.*;
import org.springframework.boot.test.autoconfigure.json.*;
import org.springframework.boot.test.context.*;
import org.springframework.boot.test.json.*;
import static org.assertj.core.api.Assertions.*;
@JsonTest
class MyJsonTests {
@Autowired
private JacksonTester<VehicleDetails> json;
@Test
void testSerialize() throws Exception {
VehicleDetails details = new VehicleDetails("Honda", "Civic");
// Assert against a `.json` file in the same package as the test
assertThat(this.json.write(details)).isEqualToJson("expected.json");
// Or use JSON path based assertions
assertThat(this.json.write(details)).hasJsonPathStringValue("@.make");
assertThat(this.json.write(details)).extractingJsonPathStringValue("@.make")
.isEqualTo("Honda");
}
@Test
void testDeserialize() throws Exception {
String content = "{\"make\":\"Ford\",\"model\":\"Focus\"}";
assertThat(this.json.parse(content))
.isEqualTo(new VehicleDetails("Ford", "Focus"));
assertThat(this.json.parseObject(content).getMake()).isEqualTo("Ford");
}
}
JSON helper classes can also be used directly in standard unit tests. To do so,
call the initFields method of the helper in your @Before method if you do not use
@JsonTest .
|
If you’re using Spring Boot’s AssertJ-based helpers to assert on a number value
at a given JSON path, you might not be able to use isEqualTo
depending on the type.
Instead, you can use AssertJ’s satisfies
to assert that the value matches the given
condition. For instance, the following example asserts that the actual number is a float
value close to 0.15
within an offset of 0.01
.
assertThat(json.write(message))
.extractingJsonPathNumberValue("@.test.numberValue")
.satisfies((number) -> assertThat(number.floatValue()).isCloseTo(0.15f, within(0.01f)));
Auto-configured Spring MVC Tests
To test whether Spring MVC controllers are working as expected, use the @WebMvcTest
annotation. @WebMvcTest
auto-configures the Spring MVC infrastructure and limits
scanned beans to @Controller
, @ControllerAdvice
, @JsonComponent
, Converter
,
GenericConverter
, Filter
, HandlerInterceptor
, WebMvcConfigurer
, and
HandlerMethodArgumentResolver
. Regular @Component
beans are not scanned when using
this annotation.
A list of the auto-configuration settings that are enabled by @WebMvcTest can be
found in the appendix.
|
If you need to register extra components, such as the Jackson Module , you can
import additional configuration classes by using @Import on your test.
|
Often, @WebMvcTest
is limited to a single controller and is used in combination with
@MockBean
to provide mock implementations for required collaborators.
@WebMvcTest
also auto-configures MockMvc
. Mock MVC offers a powerful way to quickly
test MVC controllers without needing to start a full HTTP server.
You can also auto-configure MockMvc in a non-@WebMvcTest (such as
@SpringBootTest ) by annotating it with @AutoConfigureMockMvc . The following example
uses MockMvc :
|
import org.junit.jupiter.api.*;
import org.springframework.beans.factory.annotation.*;
import org.springframework.boot.test.autoconfigure.web.servlet.*;
import org.springframework.boot.test.mock.mockito.*;
import static org.assertj.core.api.Assertions.*;
import static org.mockito.BDDMockito.*;
import static org.springframework.test.web.servlet.request.MockMvcRequestBuilders.*;
import static org.springframework.test.web.servlet.result.MockMvcResultMatchers.*;
@WebMvcTest(UserVehicleController.class)
class MyControllerTests {
@Autowired
private MockMvc mvc;
@MockBean
private UserVehicleService userVehicleService;
@Test
void testExample() throws Exception {
given(this.userVehicleService.getVehicleDetails("sboot"))
.willReturn(new VehicleDetails("Honda", "Civic"));
this.mvc.perform(get("/sboot/vehicle").accept(MediaType.TEXT_PLAIN))
.andExpect(status().isOk()).andExpect(content().string("Honda Civic"));
}
}
If you need to configure elements of the auto-configuration (for example, when
servlet filters should be applied) you can use attributes in the @AutoConfigureMockMvc
annotation.
|
If you use HtmlUnit or Selenium, auto-configuration also provides an HTMLUnit WebClient
bean and/or a WebDriver
bean. The following example uses HtmlUnit:
import com.gargoylesoftware.htmlunit.*;
import org.junit.jupiter.api.*;
import org.springframework.beans.factory.annotation.*;
import org.springframework.boot.test.autoconfigure.web.servlet.*;
import org.springframework.boot.test.mock.mockito.*;
import static org.assertj.core.api.Assertions.*;
import static org.mockito.BDDMockito.*;
@WebMvcTest(UserVehicleController.class)
class MyHtmlUnitTests {
@Autowired
private WebClient webClient;
@MockBean
private UserVehicleService userVehicleService;
@Test
void testExample() throws Exception {
given(this.userVehicleService.getVehicleDetails("sboot"))
.willReturn(new VehicleDetails("Honda", "Civic"));
HtmlPage page = this.webClient.getPage("/sboot/vehicle.html");
assertThat(page.getBody().getTextContent()).isEqualTo("Honda Civic");
}
}
By default, Spring Boot puts WebDriver beans in a special “scope” to ensure
that the driver exits after each test and that a new instance is injected. If you do
not want this behavior, you can add @Scope("singleton") to your WebDriver @Bean
definition.
|
The webDriver scope created by Spring Boot will replace any user defined scope
of the same name. If you define your own webDriver scope you may find it stops working
when you use @WebMvcTest .
|
If you have Spring Security on the classpath, @WebMvcTest
will also scan WebSecurityConfigurer
beans. Instead of disabling security completely for such tests, you can use Spring Security’s test support.
More details on how to use Spring Security’s MockMvc
support can be found in
this Testing With Spring Security how-to section.
Sometimes writing Spring MVC tests is not enough; Spring Boot can help you run full end-to-end tests with an actual server. |
Auto-configured Spring WebFlux Tests
To test that Spring WebFlux controllers are
working as expected, you can use the @WebFluxTest
annotation. @WebFluxTest
auto-configures the Spring WebFlux infrastructure and limits scanned beans to
@Controller
, @ControllerAdvice
, @JsonComponent
, Converter
, GenericConverter
,
WebFilter
, and WebFluxConfigurer
. Regular @Component
beans are not scanned when the
@WebFluxTest
annotation is used.
A list of the auto-configurations that are enabled by @WebFluxTest can be
found in the appendix.
|
If you need to register extra components, such as Jackson Module , you can import
additional configuration classes using @Import on your test.
|
Often, @WebFluxTest
is limited to a single controller and used in combination with the
@MockBean
annotation to provide mock implementations for required collaborators.
@WebFluxTest
also auto-configures
WebTestClient
, which offers
a powerful way to quickly test WebFlux controllers without needing to start a full HTTP
server.
You can also auto-configure WebTestClient in a non-@WebFluxTest (such as
@SpringBootTest ) by annotating it with @AutoConfigureWebTestClient . The following
example shows a class that uses both @WebFluxTest and a WebTestClient :
|
import org.junit.jupiter.api.Test;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.autoconfigure.web.reactive.WebFluxTest;
import org.springframework.http.MediaType;
import org.springframework.test.web.reactive.server.WebTestClient;
@WebFluxTest(UserVehicleController.class)
class MyControllerTests {
@Autowired
private WebTestClient webClient;
@MockBean
private UserVehicleService userVehicleService;
@Test
void testExample() throws Exception {
given(this.userVehicleService.getVehicleDetails("sboot"))
.willReturn(new VehicleDetails("Honda", "Civic"));
this.webClient.get().uri("/sboot/vehicle").accept(MediaType.TEXT_PLAIN)
.exchange()
.expectStatus().isOk()
.expectBody(String.class).isEqualTo("Honda Civic");
}
}
This setup is only supported by WebFlux applications as using WebTestClient in a
mocked web application only works with WebFlux at the moment.
|
@WebFluxTest cannot detect routes registered via the functional web framework. For
testing RouterFunction beans in the context, consider importing your RouterFunction
yourself via @Import or using @SpringBootTest .
|
@WebFluxTest cannot detect custom security configuration registered via a @Bean
of type SecurityWebFilterChain . To include that in your test, you will need to import
the configuration that registers the bean via @Import or use @SpringBootTest .
|
Sometimes writing Spring WebFlux tests is not enough; Spring Boot can help you run full end-to-end tests with an actual server. |
Auto-configured Data JPA Tests
You can use the @DataJpaTest
annotation to test JPA applications. By default, it scans
for @Entity
classes and configures Spring Data JPA repositories. If an embedded database
is available on the classpath, it configures one as well. Regular @Component
beans are
not loaded into the ApplicationContext
.
A list of the auto-configuration settings that are enabled by @DataJpaTest can be
found in the appendix.
|
By default, data JPA tests are transactional and roll back at the end of each test. See the relevant section in the Spring Framework Reference Documentation for more details. If that is not what you want, you can disable transaction management for a test or for the whole class as follows:
import org.junit.jupiter.api.Test;
import org.springframework.boot.test.autoconfigure.orm.jpa.DataJpaTest;
import org.springframework.transaction.annotation.Propagation;
import org.springframework.transaction.annotation.Transactional;
@DataJpaTest
@Transactional(propagation = Propagation.NOT_SUPPORTED)
class ExampleNonTransactionalTests {
}
Data JPA tests may also inject a
TestEntityManager
bean, which provides an alternative to the standard JPA EntityManager
that is
specifically designed for tests. If you want to use TestEntityManager
outside of
@DataJpaTest
instances, you can also use the @AutoConfigureTestEntityManager
annotation. A JdbcTemplate
is also available if you need that. The following example
shows the @DataJpaTest
annotation in use:
import org.junit.jupiter.api.Test;
import org.springframework.boot.test.autoconfigure.orm.jpa.*;
import static org.assertj.core.api.Assertions.*;
@DataJpaTest
class ExampleRepositoryTests {
@Autowired
private TestEntityManager entityManager;
@Autowired
private UserRepository repository;
@Test
void testExample() throws Exception {
this.entityManager.persist(new User("sboot", "1234"));
User user = this.repository.findByUsername("sboot");
assertThat(user.getUsername()).isEqualTo("sboot");
assertThat(user.getVin()).isEqualTo("1234");
}
}
In-memory embedded databases generally work well for tests, since they are fast and do
not require any installation. If, however, you prefer to run tests against a real
database you can use the @AutoConfigureTestDatabase
annotation, as shown in the
following example:
@DataJpaTest
@AutoConfigureTestDatabase(replace=Replace.NONE)
class ExampleRepositoryTests {
// ...
}
Auto-configured JDBC Tests
@JdbcTest
is similar to @DataJpaTest
but is for tests that only require a
DataSource
and do not use Spring Data JDBC. By default, it configures an in-memory
embedded database and a JdbcTemplate
. Regular @Component
beans are not loaded into
the ApplicationContext
.
A list of the auto-configurations that are enabled by @JdbcTest can be
found in the appendix.
|
By default, JDBC tests are transactional and roll back at the end of each test. See the relevant section in the Spring Framework Reference Documentation for more details. If that is not what you want, you can disable transaction management for a test or for the whole class, as follows:
import org.junit.jupiter.api.Test;
import org.springframework.boot.test.autoconfigure.jdbc.JdbcTest;
import org.springframework.transaction.annotation.Propagation;
import org.springframework.transaction.annotation.Transactional;
@JdbcTest
@Transactional(propagation = Propagation.NOT_SUPPORTED)
class ExampleNonTransactionalTests {
}
If you prefer your test to run against a real database, you can use the
@AutoConfigureTestDatabase
annotation in the same way as for DataJpaTest
. (See
"Auto-configured Data JPA Tests".)
Auto-configured Data JDBC Tests
@DataJdbcTest
is similar to @JdbcTest
but is for tests that use Spring Data JDBC
repositories. By default, it configures an in-memory embedded database, a JdbcTemplate
,
and Spring Data JDBC repositories. Regular @Component
beans are not loaded into
the ApplicationContext
.
A list of the auto-configurations that are enabled by @DataJdbcTest can be
found in the appendix.
|
By default, Data JDBC tests are transactional and roll back at the end of each test. See the relevant section in the Spring Framework Reference Documentation for more details. If that is not what you want, you can disable transaction management for a test or for the whole test class as shown in the JDBC example.
If you prefer your test to run against a real database, you can use the
@AutoConfigureTestDatabase
annotation in the same way as for DataJpaTest
. (See
"Auto-configured Data JPA Tests".)
Auto-configured jOOQ Tests
You can use @JooqTest
in a similar fashion as @JdbcTest
but for jOOQ-related tests.
As jOOQ relies heavily on a Java-based schema that corresponds with the database schema,
the existing DataSource
is used. If you want to replace it with an in-memory database,
you can use @AutoConfigureTestDatabase
to override those settings. (For more about using
jOOQ with Spring Boot, see "Using jOOQ", earlier in this chapter.) Regular
@Component
beans are not loaded into the ApplicationContext
.
A list of the auto-configurations that are enabled by @JooqTest can be
found in the appendix.
|
@JooqTest
configures a DSLContext
. Regular @Component
beans are not loaded into the
ApplicationContext
. The following example shows the @JooqTest
annotation in use:
import org.jooq.DSLContext;
import org.junit.jupiter.api.Test;
import org.springframework.boot.test.autoconfigure.jooq.JooqTest;
@JooqTest
class ExampleJooqTests {
@Autowired
private DSLContext dslContext;
}
JOOQ tests are transactional and roll back at the end of each test by default. If that is not what you want, you can disable transaction management for a test or for the whole test class as shown in the JDBC example.
Auto-configured Data MongoDB Tests
You can use @DataMongoTest
to test MongoDB applications. By default, it configures an
in-memory embedded MongoDB (if available), configures a MongoTemplate
, scans for
@Document
classes, and configures Spring Data MongoDB repositories. Regular
@Component
beans are not loaded into the ApplicationContext
. (For more about using
MongoDB with Spring Boot, see "MongoDB", earlier in this chapter.)
A list of the auto-configuration settings that are enabled by @DataMongoTest can be
found in the appendix.
|
The following class shows the @DataMongoTest
annotation in use:
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.autoconfigure.data.mongo.DataMongoTest;
import org.springframework.data.mongodb.core.MongoTemplate;
@DataMongoTest
class ExampleDataMongoTests {
@Autowired
private MongoTemplate mongoTemplate;
//
}
In-memory embedded MongoDB generally works well for tests, since it is fast and does not require any developer installation. If, however, you prefer to run tests against a real MongoDB server, you should exclude the embedded MongoDB auto-configuration, as shown in the following example:
import org.springframework.boot.autoconfigure.mongo.embedded.EmbeddedMongoAutoConfiguration;
import org.springframework.boot.test.autoconfigure.data.mongo.DataMongoTest;
@DataMongoTest(excludeAutoConfiguration = EmbeddedMongoAutoConfiguration.class)
class ExampleDataMongoNonEmbeddedTests {
}
Auto-configured Data Neo4j Tests
You can use @DataNeo4jTest
to test Neo4j applications. By default, it uses an in-memory
embedded Neo4j (if the embedded driver is available), scans for @NodeEntity
classes, and
configures Spring Data Neo4j repositories. Regular @Component
beans are not loaded into
the ApplicationContext
. (For more about using Neo4J with Spring Boot, see
"Neo4j", earlier in this chapter.)
A list of the auto-configuration settings that are enabled by @DataNeo4jTest can be
found in the appendix.
|
The following example shows a typical setup for using Neo4J tests in Spring Boot:
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.autoconfigure.data.neo4j.DataNeo4jTest;
@DataNeo4jTest
class ExampleDataNeo4jTests {
@Autowired
private YourRepository repository;
//
}
By default, Data Neo4j tests are transactional and roll back at the end of each test. See the relevant section in the Spring Framework Reference Documentation for more details. If that is not what you want, you can disable transaction management for a test or for the whole class, as follows:
import org.springframework.boot.test.autoconfigure.data.neo4j.DataNeo4jTest;
import org.springframework.transaction.annotation.Propagation;
import org.springframework.transaction.annotation.Transactional;
@DataNeo4jTest
@Transactional(propagation = Propagation.NOT_SUPPORTED)
class ExampleNonTransactionalTests {
}
Auto-configured Data Redis Tests
You can use @DataRedisTest
to test Redis applications. By default, it scans for
@RedisHash
classes and configures Spring Data Redis repositories. Regular @Component
beans are not loaded into the ApplicationContext
. (For more about using Redis with
Spring Boot, see "Redis", earlier in this chapter.)
A list of the auto-configuration settings that are enabled by @DataRedisTest can be
found in the appendix.
|
The following example shows the @DataRedisTest
annotation in use:
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.autoconfigure.data.redis.DataRedisTest;
@DataRedisTest
class ExampleDataRedisTests {
@Autowired
private YourRepository repository;
//
}
Auto-configured Data LDAP Tests
You can use @DataLdapTest
to test LDAP applications. By default, it configures an
in-memory embedded LDAP (if available), configures an LdapTemplate
, scans for @Entry
classes, and configures Spring Data LDAP repositories. Regular @Component
beans are not
loaded into the ApplicationContext
. (For more about using LDAP with
Spring Boot, see "LDAP", earlier in this chapter.)
A list of the auto-configuration settings that are enabled by @DataLdapTest can be
found in the appendix.
|
The following example shows the @DataLdapTest
annotation in use:
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.autoconfigure.data.ldap.DataLdapTest;
import org.springframework.ldap.core.LdapTemplate;
@DataLdapTest
class ExampleDataLdapTests {
@Autowired
private LdapTemplate ldapTemplate;
//
}
In-memory embedded LDAP generally works well for tests, since it is fast and does not require any developer installation. If, however, you prefer to run tests against a real LDAP server, you should exclude the embedded LDAP auto-configuration, as shown in the following example:
import org.springframework.boot.autoconfigure.ldap.embedded.EmbeddedLdapAutoConfiguration;
import org.springframework.boot.test.autoconfigure.data.ldap.DataLdapTest;
@DataLdapTest(excludeAutoConfiguration = EmbeddedLdapAutoConfiguration.class)
class ExampleDataLdapNonEmbeddedTests {
}
Auto-configured REST Clients
You can use the @RestClientTest
annotation to test REST clients. By default, it
auto-configures Jackson, GSON, and Jsonb support, configures a RestTemplateBuilder
, and
adds support for MockRestServiceServer
. Regular @Component
beans are not loaded into
the ApplicationContext
.
A list of the auto-configuration settings that are enabled by @RestClientTest can
be found in the appendix.
|
The specific beans that you want to test should be specified by using the value
or
components
attribute of @RestClientTest
, as shown in the following example:
@RestClientTest(RemoteVehicleDetailsService.class)
class ExampleRestClientTest {
@Autowired
private RemoteVehicleDetailsService service;
@Autowired
private MockRestServiceServer server;
@Test
void getVehicleDetailsWhenResultIsSuccessShouldReturnDetails()
throws Exception {
this.server.expect(requestTo("/greet/details"))
.andRespond(withSuccess("hello", MediaType.TEXT_PLAIN));
String greeting = this.service.callRestService();
assertThat(greeting).isEqualTo("hello");
}
}
Auto-configured Spring REST Docs Tests
You can use the @AutoConfigureRestDocs
annotation to use Spring REST
Docs in your tests with Mock MVC, REST Assured, or WebTestClient. It removes the need for
the JUnit extension in Spring REST Docs.
@AutoConfigureRestDocs
can be used to override the default output directory
(target/generated-snippets
if you are using Maven or build/generated-snippets
if you
are using Gradle). It can also be used to configure the host, scheme, and port that
appears in any documented URIs.
Auto-configured Spring REST Docs Tests with Mock MVC
@AutoConfigureRestDocs
customizes the MockMvc
bean to use Spring REST Docs. You can
inject it by using @Autowired
and use it in your tests as you normally would when using
Mock MVC and Spring REST Docs, as shown in the following example:
import org.junit.jupiter.api.Test;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.autoconfigure.web.servlet.WebMvcTest;
import org.springframework.http.MediaType;
import org.springframework.test.web.servlet.MockMvc;
import static org.springframework.restdocs.mockmvc.MockMvcRestDocumentation.document;
import static org.springframework.test.web.servlet.request.MockMvcRequestBuilders.get;
import static org.springframework.test.web.servlet.result.MockMvcResultMatchers.*;
@WebMvcTest(UserController.class)
@AutoConfigureRestDocs
class UserDocumentationTests {
@Autowired
private MockMvc mvc;
@Test
void listUsers() throws Exception {
this.mvc.perform(get("/users").accept(MediaType.TEXT_PLAIN))
.andExpect(status().isOk())
.andDo(document("list-users"));
}
}
If you require more control over Spring REST Docs configuration than offered by the
attributes of @AutoConfigureRestDocs
, you can use a
RestDocsMockMvcConfigurationCustomizer
bean, as shown in the following example:
@TestConfiguration
static class CustomizationConfiguration
implements RestDocsMockMvcConfigurationCustomizer {
@Override
public void customize(MockMvcRestDocumentationConfigurer configurer) {
configurer.snippets().withTemplateFormat(TemplateFormats.markdown());
}
}
If you want to make use of Spring REST Docs support for a parameterized output directory,
you can create a RestDocumentationResultHandler
bean. The auto-configuration calls
alwaysDo
with this result handler, thereby causing each MockMvc
call to automatically
generate the default snippets. The following example shows a
RestDocumentationResultHandler
being defined:
@TestConfiguration
static class ResultHandlerConfiguration {
@Bean
public RestDocumentationResultHandler restDocumentation() {
return MockMvcRestDocumentation.document("{method-name}");
}
}
Auto-configured Spring REST Docs Tests with WebTestClient
@AutoConfigureRestDocs
can also be used with WebTestClient
. You can inject it by using
@Autowired
and use it in your tests as you normally would when using @WebFluxTest
and
Spring REST Docs, as shown in the following example:
import org.junit.jupiter.api.Test;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.autoconfigure.restdocs.AutoConfigureRestDocs;
import org.springframework.boot.test.autoconfigure.web.reactive.WebFluxTest;
import org.springframework.test.web.reactive.server.WebTestClient;
import static org.springframework.restdocs.webtestclient.WebTestClientRestDocumentation.document;
@WebFluxTest
@AutoConfigureRestDocs
class UsersDocumentationTests {
@Autowired
private WebTestClient webTestClient;
@Test
void listUsers() {
this.webTestClient.get().uri("/").exchange().expectStatus().isOk().expectBody()
.consumeWith(document("list-users"));
}
}
If you require more control over Spring REST Docs configuration than offered by the
attributes of @AutoConfigureRestDocs
, you can use a
RestDocsWebTestClientConfigurationCustomizer
bean, as shown in the following example:
@TestConfiguration
public static class CustomizationConfiguration implements RestDocsWebTestClientConfigurationCustomizer {
@Override
public void customize(WebTestClientRestDocumentationConfigurer configurer) {
configurer.snippets().withEncoding("UTF-8");
}
}
Auto-configured Spring REST Docs Tests with REST Assured
@AutoConfigureRestDocs
makes a RequestSpecification
bean, preconfigured to use Spring
REST Docs, available to your tests. You can inject it by using @Autowired
and use it in
your tests as you normally would when using REST Assured and Spring REST Docs, as shown
in the following example:
import io.restassured.specification.RequestSpecification;
import org.junit.jupiter.api.Test;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.autoconfigure.restdocs.AutoConfigureRestDocs;
import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.boot.test.context.SpringBootTest.WebEnvironment;
import org.springframework.boot.web.server.LocalServerPort;
import static io.restassured.RestAssured.given;
import static org.hamcrest.Matchers.is;
import static org.springframework.restdocs.restassured3.RestAssuredRestDocumentation.document;
@SpringBootTest(webEnvironment = WebEnvironment.RANDOM_PORT)
@AutoConfigureRestDocs
class UserDocumentationTests {
@Test
void listUsers(@Autowired RequestSpecification documentationSpec, @LocalServerPort int port) {
given(documentationSpec).filter(document("list-users")).when().port(port).get("/").then().assertThat()
.statusCode(is(200));
}
}
If you require more control over Spring REST Docs configuration than offered by the
attributes of @AutoConfigureRestDocs
, a RestDocsRestAssuredConfigurationCustomizer
bean can be used, as shown in the following example:
@TestConfiguration
public static class CustomizationConfiguration implements RestDocsRestAssuredConfigurationCustomizer {
@Override
public void customize(RestAssuredRestDocumentationConfigurer configurer) {
configurer.snippets().withTemplateFormat(TemplateFormats.markdown());
}
}
Additional Auto-configuration and Slicing
Each slice provides one or more @AutoConfigure…
annotations that namely defines the
auto-configurations that should be included as part of a slice. Additional
auto-configurations can be added by creating a custom @AutoConfigure…
annotation or
simply by adding @ImportAutoConfiguration
to the test as shown in the following example:
@JdbcTest
@ImportAutoConfiguration(IntegrationAutoConfiguration.class)
class ExampleJdbcTests {
}
Make sure to not use the regular @Import annotation to import auto-configurations
as they are handled in a specific way by Spring Boot.
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User Configuration and Slicing
If you structure your code in a sensible way, your
@SpringBootApplication
class is
used by default as
the configuration of your tests.
It then becomes important not to litter the application’s main class with configuration settings that are specific to a particular area of its functionality.
Assume that you are using Spring Batch and you rely on the auto-configuration for it.
You could define your @SpringBootApplication
as follows:
@SpringBootApplication
@EnableBatchProcessing
public class SampleApplication { ... }
Because this class is the source configuration for the test, any slice test actually
tries to start Spring Batch, which is definitely not what you want to do. A recommended
approach is to move that area-specific configuration to a separate @Configuration
class
at the same level as your application, as shown in the following example:
@Configuration(proxyBeanMethods = false)
@EnableBatchProcessing
public class BatchConfiguration { ... }
Depending on the complexity of your application, you may either have a single
@Configuration class for your customizations or one class per domain area. The latter
approach lets you enable it in one of your tests, if necessary, with the @Import
annotation.
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Test slices exclude @Configuration
classes from scanning. For example, for a @WebMvcTest
,
the following configuration will not include the given WebMvcConfigurer
bean in the application
context loaded by the test slice:
@Configuration
public class WebConfiguration {
@Bean
public WebMvcConfigurer testConfigurer() {
return new WebMvcConfigurer() {
...
};
}
}
The configuration below will, however, cause the custom WebMvcConfigurer
to be loaded
by the test slice.
@Component
public class TestWebMvcConfigurer implements WebMvcConfigurer {
...
}
Another source of confusion is classpath scanning. Assume that, while you structured your code in a sensible way, you need to scan an additional package. Your application may resemble the following code:
@SpringBootApplication
@ComponentScan({ "com.example.app", "org.acme.another" })
public class SampleApplication { ... }
Doing so effectively overrides the default component scan directive with the side effect
of scanning those two packages regardless of the slice that you chose. For instance, a
@DataJpaTest
seems to suddenly scan components and user configurations of your
application. Again, moving the custom directive to a separate class is a good way to fix
this issue.
If this is not an option for you, you can create a @SpringBootConfiguration
somewhere in the hierarchy of your test so that it is used instead. Alternatively, you
can specify a source for your test, which disables the behavior of finding a default one.
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Using Spock to Test Spring Boot Applications
If you wish to use Spock to test a Spring Boot application, you should add a dependency
on Spock’s spock-spring
module to your application’s build. spock-spring
integrates
Spring’s test framework into Spock. It is recommended that you use Spock 1.2 or later to
benefit from a number of improvements to Spock’s Spring Framework and Spring Boot
integration. See the
documentation for Spock’s Spring module for further details.
4.25.4. Test Utilities
A few test utility classes that are generally useful when testing your application are
packaged as part of spring-boot
.
ConfigFileApplicationContextInitializer
ConfigFileApplicationContextInitializer
is an ApplicationContextInitializer
that you
can apply to your tests to load Spring Boot application.properties
files. You can use
it when you do not need the full set of features provided by @SpringBootTest
, as shown
in the following example:
@ContextConfiguration(classes = Config.class,
initializers = ConfigFileApplicationContextInitializer.class)
Using ConfigFileApplicationContextInitializer alone does not provide support for
@Value("${…}") injection. Its only job is to ensure that application.properties
files are loaded into Spring’s Environment . For @Value support, you need to either
additionally configure a PropertySourcesPlaceholderConfigurer or use @SpringBootTest ,
which auto-configures one for you.
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TestPropertyValues
TestPropertyValues
lets you quickly add properties to a
ConfigurableEnvironment
or ConfigurableApplicationContext
. You can call it with
key=value
strings, as follows:
TestPropertyValues.of("org=Spring", "name=Boot").applyTo(env);
OutputCapture
OutputCapture
is a JUnit Extension
that you can use to capture System.out
and
System.err
output. To use with {@link ExtendWith @ExtendWith}, you can inject
CapturedOutput
as an argument to your test class constructor or test method as follows:
import org.junit.jupiter.api.Test;
import org.junit.jupiter.api.extension.ExtendWith;
import org.springframework.boot.test.system.CapturedOutput;
import org.springframework.boot.test.system.OutputCaptureExtension;
import static org.assertj.core.api.Assertions.assertThat;
@ExtendWith(OutputCaptureExtension.class)
class MyTest {
@Test
void testName(CapturedOutput output) {
System.out.println("Hello World!");
assertThat(output).contains("World"));
}
}
TestRestTemplate
Spring Framework 5.0 provides a new WebTestClient that works for
WebFlux integration tests and both
WebFlux and MVC end-to-end testing. It provides a fluent API for assertions,
unlike TestRestTemplate .
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TestRestTemplate
is a convenience alternative to Spring’s RestTemplate
that is useful
in integration tests. You can get a vanilla template or one that sends Basic HTTP
authentication (with a username and password). In either case, the template behaves in a
test-friendly way by not throwing exceptions on server-side errors. It is recommended,
but not mandatory, to use the Apache HTTP Client (version 4.3.2 or better). If you have
that on your classpath, the TestRestTemplate
responds by configuring the client
appropriately. If you do use Apache’s HTTP client, some additional test-friendly features
are enabled:
-
Redirects are not followed (so you can assert the response location).
-
Cookies are ignored (so the template is stateless).
TestRestTemplate
can be instantiated directly in your integration tests, as shown in
the following example:
public class MyTest {
private TestRestTemplate template = new TestRestTemplate();
@Test
public void testRequest() throws Exception {
HttpHeaders headers = this.template.getForEntity(
"https://myhost.example.com/example", String.class).getHeaders();
assertThat(headers.getLocation()).hasHost("other.example.com");
}
}
Alternatively, if you use the @SpringBootTest
annotation with
WebEnvironment.RANDOM_PORT
or WebEnvironment.DEFINED_PORT
, you can inject a
fully configured TestRestTemplate
and start using it. If necessary, additional
customizations can be applied through the RestTemplateBuilder
bean. Any URLs that do
not specify a host and port automatically connect to the embedded server, as shown in the
following example:
@SpringBootTest(webEnvironment = WebEnvironment.RANDOM_PORT)
class SampleWebClientTests {
@Autowired
private TestRestTemplate template;
@Test
void testRequest() {
HttpHeaders headers = this.template.getForEntity("/example", String.class).getHeaders();
assertThat(headers.getLocation()).hasHost("other.example.com");
}
@TestConfiguration
static class Config {
@Bean
RestTemplateBuilder restTemplateBuilder() {
return new RestTemplateBuilder().setConnectTimeout(Duration.ofSeconds(1))
.setReadTimeout(Duration.ofSeconds(1));
}
}
}
4.26. WebSockets
Spring Boot provides WebSockets auto-configuration for embedded Tomcat, Jetty, and Undertow. If you deploy a war file to a standalone container, Spring Boot assumes that the container is responsible for the configuration of its WebSocket support.
Spring Framework provides rich WebSocket support
for MVC web applications that can be easily accessed through the
spring-boot-starter-websocket
module.
WebSocket support is also available for
reactive web applications and
requires to include the WebSocket API alongside spring-boot-starter-webflux
:
<dependency>
<groupId>javax.websocket</groupId>
<artifactId>javax.websocket-api</artifactId>
</dependency>
4.27. Web Services
Spring Boot provides Web Services auto-configuration so that all you must do is define
your Endpoints
.
The Spring Web Services features can be easily accessed
with the spring-boot-starter-webservices
module.
SimpleWsdl11Definition
and SimpleXsdSchema
beans can be automatically created for
your WSDLs and XSDs respectively. To do so, configure their location, as shown in the
following example:
spring.webservices.wsdl-locations=classpath:/wsdl
4.27.1. Calling Web Services with WebServiceTemplate
If you need to call remote Web services from your application, you can use the
WebServiceTemplate
class.
Since WebServiceTemplate
instances often need to be customized before being used, Spring
Boot does not provide any single auto-configured WebServiceTemplate
bean. It does,
however, auto-configure a WebServiceTemplateBuilder
, which can be used to create
WebServiceTemplate
instances when needed.
The following code shows a typical example:
@Service
public class MyService {
private final WebServiceTemplate webServiceTemplate;
public MyService(WebServiceTemplateBuilder webServiceTemplateBuilder) {
this.webServiceTemplate = webServiceTemplateBuilder.build();
}
public DetailsResp someWsCall(DetailsReq detailsReq) {
return (DetailsResp) this.webServiceTemplate.marshalSendAndReceive(detailsReq, new SoapActionCallback(ACTION));
}
}
By default, WebServiceTemplateBuilder
detects a suitable HTTP-based
WebServiceMessageSender
using the available HTTP client libraries on the classpath. You
can also customize read and connection timeouts as follows:
@Bean
public WebServiceTemplate webServiceTemplate(WebServiceTemplateBuilder builder) {
return builder.messageSenders(new HttpWebServiceMessageSenderBuilder()
.setConnectTimeout(5000).setReadTimeout(2000).build()).build();
}
4.28. Creating Your Own Auto-configuration
If you work in a company that develops shared libraries, or if you work on an open-source or commercial library, you might want to develop your own auto-configuration. Auto-configuration classes can be bundled in external jars and still be picked-up by Spring Boot.
Auto-configuration can be associated to a “starter” that provides the auto-configuration code as well as the typical libraries that you would use with it. We first cover what you need to know to build your own auto-configuration and then we move on to the typical steps required to create a custom starter.
A demo project is available to showcase how you can create a starter step-by-step. |
4.28.1. Understanding Auto-configured Beans
Under the hood, auto-configuration is implemented with standard @Configuration
classes.
Additional @Conditional
annotations are used to constrain when the auto-configuration
should apply. Usually, auto-configuration classes use @ConditionalOnClass
and
@ConditionalOnMissingBean
annotations. This ensures that auto-configuration applies
only when relevant classes are found and when you have not declared your own
@Configuration
.
You can browse the source code of spring-boot-autoconfigure
to see the @Configuration
classes that Spring provides (see the
META-INF/spring.factories
file).
4.28.2. Locating Auto-configuration Candidates
Spring Boot checks for the presence of a META-INF/spring.factories
file within your
published jar. The file should list your configuration classes under the
EnableAutoConfiguration
key, as shown in the following example:
org.springframework.boot.autoconfigure.EnableAutoConfiguration=\ com.mycorp.libx.autoconfigure.LibXAutoConfiguration,\ com.mycorp.libx.autoconfigure.LibXWebAutoConfiguration
Auto-configurations must be loaded that way only. Make sure that they are defined in
a specific package space and that they are never the target of component scanning.
Furthermore, auto-configuration classes should not enable component scanning to find
additional components. Specific |
You can use the
@AutoConfigureAfter
or
@AutoConfigureBefore
annotations if your configuration needs to be applied in a specific order. For example,
if you provide web-specific configuration, your class may need to be applied after
WebMvcAutoConfiguration
.
If you want to order certain auto-configurations that should not have any direct
knowledge of each other, you can also use @AutoConfigureOrder
. That annotation has the
same semantic as the regular @Order
annotation but provides a dedicated order for
auto-configuration classes.
4.28.3. Condition Annotations
You almost always want to include one or more @Conditional
annotations on your
auto-configuration class. The @ConditionalOnMissingBean
annotation is one common
example that is used to allow developers to override auto-configuration if they are
not happy with your defaults.
Spring Boot includes a number of @Conditional
annotations that you can reuse in your
own code by annotating @Configuration
classes or individual @Bean
methods. These
annotations include:
Class Conditions
The @ConditionalOnClass
and @ConditionalOnMissingClass
annotations let
@Configuration
classes be included based on the presence or absence of specific classes.
Due to the fact that annotation metadata is parsed by using ASM, you
can use the value
attribute to refer to the real class, even though that class might not
actually appear on the running application classpath. You can also use the name
attribute if you prefer to specify the class name by using a String
value.
This mechanism does not apply the same way to @Bean
methods where typically the return
type is the target of the condition: before the condition on the method applies, the JVM
will have loaded the class and potentially processed method references which will fail if
the class is not present.
To handle this scenario, a separate @Configuration
class can be used to isolate the
condition, as shown in the following example:
@Configuration(proxyBeanMethods = false)
// Some conditions
public class MyAutoConfiguration {
// Auto-configured beans
@Configuration(proxyBeanMethods = false)
@ConditionalOnClass(EmbeddedAcmeService.class)
static class EmbeddedConfiguration {
@Bean
@ConditionalOnMissingBean
public EmbeddedAcmeService embeddedAcmeService() { ... }
}
}
If you use |
Bean Conditions
The @ConditionalOnBean
and @ConditionalOnMissingBean
annotations let a bean be
included based on the presence or absence of specific beans. You can use the value
attribute to specify beans by type or name
to specify beans by name. The search
attribute lets you limit the ApplicationContext
hierarchy that should be considered
when searching for beans.
When placed on a @Bean
method, the target type defaults to the return type of the
method, as shown in the following example:
@Configuration(proxyBeanMethods = false)
public class MyAutoConfiguration {
@Bean
@ConditionalOnMissingBean
public MyService myService() { ... }
}
In the preceding example, the myService
bean is going to be created if no bean of type
MyService
is already contained in the ApplicationContext
.
You need to be very careful about the order in which bean definitions are added, as
these conditions are evaluated based on what has been processed so far. For this reason,
we recommend using only @ConditionalOnBean and @ConditionalOnMissingBean annotations
on auto-configuration classes (since these are guaranteed to load after any user-defined
bean definitions have been added).
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@ConditionalOnBean and @ConditionalOnMissingBean do not prevent @Configuration
classes from being created. The only difference between using these conditions at the class level
and marking each contained @Bean method with the annotation is that the former prevents
registration of the @Configuration class as a bean if the condition does not match.
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Property Conditions
The @ConditionalOnProperty
annotation lets configuration be included based on a Spring
Environment property. Use the prefix
and name
attributes to specify the property that
should be checked. By default, any property that exists and is not equal to false
is
matched. You can also create more advanced checks by using the havingValue
and
matchIfMissing
attributes.
Resource Conditions
The @ConditionalOnResource
annotation lets configuration be included only when a
specific resource is present. Resources can be specified by using the usual Spring
conventions, as shown in the following example: file:/home/user/test.dat
.
Web Application Conditions
The @ConditionalOnWebApplication
and @ConditionalOnNotWebApplication
annotations let
configuration be included depending on whether the application is a “web application”.
A web application is any application that uses a Spring WebApplicationContext
,
defines a session
scope, or has a StandardServletEnvironment
.
SpEL Expression Conditions
The @ConditionalOnExpression
annotation lets configuration be included based on the
result of a SpEL expression.
4.28.4. Testing your Auto-configuration
An auto-configuration can be affected by many factors: user configuration (@Bean
definition and Environment
customization), condition evaluation (presence of a
particular library), and others. Concretely, each test should create a well defined
ApplicationContext
that represents a combination of those customizations.
ApplicationContextRunner
provides a great way to achieve that.
ApplicationContextRunner
is usually defined as a field of the test class to gather the
base, common configuration. The following example makes sure that
UserServiceAutoConfiguration
is always invoked:
private final ApplicationContextRunner contextRunner = new ApplicationContextRunner()
.withConfiguration(AutoConfigurations.of(UserServiceAutoConfiguration.class));
If multiple auto-configurations have to be defined, there is no need to order their declarations as they are invoked in the exact same order as when running the application. |
Each test can use the runner to represent a particular use case. For instance, the sample
below invokes a user configuration (UserConfiguration
) and checks that the
auto-configuration backs off properly. Invoking run
provides a callback context that can
be used with Assert4J
.
@Test
void defaultServiceBacksOff() {
this.contextRunner.withUserConfiguration(UserConfiguration.class).run((context) -> {
assertThat(context).hasSingleBean(UserService.class);
assertThat(context).getBean("myUserService").isSameAs(context.getBean(UserService.class));
});
}
@Configuration(proxyBeanMethods = false)
static class UserConfiguration {
@Bean
UserService myUserService() {
return new UserService("mine");
}
}
It is also possible to easily customize the Environment
, as shown in the following
example:
@Test
void serviceNameCanBeConfigured() {
this.contextRunner.withPropertyValues("user.name=test123").run((context) -> {
assertThat(context).hasSingleBean(UserService.class);
assertThat(context.getBean(UserService.class).getName()).isEqualTo("test123");
});
}
The runner can also be used to display the ConditionEvaluationReport
. The report can be printed
at INFO
or DEBUG
level. The following example shows how to use the ConditionEvaluationReportLoggingListener
to print the report in auto-configuration tests.
@Test
public void autoConfigTest {
ConditionEvaluationReportLoggingListener initializer = new ConditionEvaluationReportLoggingListener(
LogLevel.INFO);
ApplicationContextRunner contextRunner = new ApplicationContextRunner()
.withInitializer(initializer).run((context) -> {
// Do something...
});
}
Simulating a Web Context
If you need to test an auto-configuration that only operates in a Servlet or Reactive web
application context, use the WebApplicationContextRunner
or
ReactiveWebApplicationContextRunner
respectively.
Overriding the Classpath
It is also possible to test what happens when a particular class and/or package is not
present at runtime. Spring Boot ships with a FilteredClassLoader
that can easily be used
by the runner. In the following example, we assert that if UserService
is not present, the
auto-configuration is properly disabled:
@Test
void serviceIsIgnoredIfLibraryIsNotPresent() {
this.contextRunner.withClassLoader(new FilteredClassLoader(UserService.class))
.run((context) -> assertThat(context).doesNotHaveBean("userService"));
}
4.28.5. Creating Your Own Starter
A full Spring Boot starter for a library may contain the following components:
-
The
autoconfigure
module that contains the auto-configuration code. -
The
starter
module that provides a dependency to theautoconfigure
module as well as the library and any additional dependencies that are typically useful. In a nutshell, adding the starter should provide everything needed to start using that library.
You may combine the auto-configuration code and the dependency management in a single module if you do not need to separate those two concerns. |
Naming
You should make sure to provide a proper namespace for your starter. Do not start your
module names with spring-boot
, even if you use a different Maven groupId
. We may
offer official support for the thing you auto-configure in the future.
As a rule of thumb, you should name a combined module after the starter. For example,
assume that you are creating a starter for "acme" and that you name the auto-configure
module acme-spring-boot-autoconfigure
and the starter acme-spring-boot-starter
. If
you only have one module that combines the two, name it acme-spring-boot-starter
.
Configuration keys
If your starter provides configuration keys, use a unique namespace for them. In
particular, do not include your keys in the namespaces that Spring Boot uses (such as
server
, management
, spring
, and so on). If you use the same namespace, we may modify
these namespaces in the future in ways that break your modules. As a rule of thumb,
prefix all your keys with a namespace that you own (e.g. acme
).
Make sure that configuration keys are documented by adding field javadoc for each property, as shown in the following example:
@ConfigurationProperties("acme")
public class AcmeProperties {
/**
* Whether to check the location of acme resources.
*/
private boolean checkLocation = true;
/**
* Timeout for establishing a connection to the acme server.
*/
private Duration loginTimeout = Duration.ofSeconds(3);
// getters & setters
}
Here are some rules we follow internally to make sure descriptions are consistent:
-
Do not start the description by "The" or "A".
-
For
boolean
types, start the description with "Whether" or "Enable". -
For collection-based types, start the description with "Comma-separated list"
-
Use
java.time.Duration
rather thanlong
and describe the default unit if it differs from milliseconds, e.g. "If a duration suffix is not specified, seconds will be used". -
Do not provide the default value in the description unless it has to be determined at runtime.
Make sure to
trigger meta-data
generation so that IDE assistance is available for your keys as well. You may want to
review the generated metadata (META-INF/spring-configuration-metadata.json
) to make
sure your keys are properly documented. Using your own starter in a compatible IDE is
also a good idea to validate that quality of the metadata.
autoconfigure
Module
The autoconfigure
module contains everything that is necessary to get started with the
library. It may also contain configuration key definitions (such as
@ConfigurationProperties
) and any callback interface that can be used to further
customize how the components are initialized.
You should mark the dependencies to the library as optional so that you can include
the autoconfigure module in your projects more easily. If you do it that way, the
library is not provided and, by default, Spring Boot backs off.
|
Spring Boot uses an annotation processor to collect the conditions on auto-configurations
in a metadata file (META-INF/spring-autoconfigure-metadata.properties
). If that file is
present, it is used to eagerly filter auto-configurations that do not match, which will
improve startup time. It is recommended to add the following dependency in a module that
contains auto-configurations:
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-autoconfigure-processor</artifactId>
<optional>true</optional>
</dependency>
With Gradle 4.5 and earlier, the dependency should be declared in the compileOnly
configuration, as shown in the following example:
dependencies {
compileOnly "org.springframework.boot:spring-boot-autoconfigure-processor"
}
With Gradle 4.6 and later, the dependency should be declared in the annotationProcessor
configuration, as shown in the following example:
dependencies {
annotationProcessor "org.springframework.boot:spring-boot-autoconfigure-processor"
}
Starter Module
The starter is really an empty jar. Its only purpose is to provide the necessary dependencies to work with the library. You can think of it as an opinionated view of what is required to get started.
Do not make assumptions about the project in which your starter is added. If the library you are auto-configuring typically requires other starters, mention them as well. Providing a proper set of default dependencies may be hard if the number of optional dependencies is high, as you should avoid including dependencies that are unnecessary for a typical usage of the library. In other words, you should not include optional dependencies.
Either way, your starter must reference the core Spring Boot starter
(spring-boot-starter ) directly or indirectly (i.e. no need to add it if your starter
relies on another starter). If a project is created with only your custom starter, Spring
Boot’s core features will be honoured by the presence of the core starter.
|
4.29. Kotlin support
Kotlin is a statically-typed language targeting the JVM (and other platforms) which allows writing concise and elegant code while providing interoperability with existing libraries written in Java.
Spring Boot provides Kotlin support by leveraging the support in other Spring projects such as Spring Framework, Spring Data, and Reactor. See the Spring Framework Kotlin support documentation for more information.
The easiest way to start with Spring Boot and Kotlin is to follow
this comprehensive tutorial. You
can create new Kotlin projects via
start.spring.io. Feel free to join the #spring
channel of Kotlin Slack or ask a question with the spring
and kotlin
tags on Stack
Overflow if you need support.
4.29.1. Requirements
Spring Boot supports Kotlin 1.3.x. To use Kotlin, org.jetbrains.kotlin:kotlin-stdlib
and
org.jetbrains.kotlin:kotlin-reflect
must be present on the classpath. The
kotlin-stdlib
variants kotlin-stdlib-jdk7
and kotlin-stdlib-jdk8
can also be used.
Since Kotlin classes are final by default, you are likely to want to configure kotlin-spring plugin in order to automatically open Spring-annotated classes so that they can be proxied.
Jackson’s Kotlin module is required for serializing / deserializing JSON data in Kotlin. It is automatically registered when found on the classpath. A warning message is logged if Jackson and Kotlin are present but the Jackson Kotlin module is not.
These dependencies and plugins are provided by default if one bootstraps a Kotlin project on start.spring.io. |
4.29.2. Null-safety
One of Kotlin’s key features is null-safety. It
deals with null
values at compile time rather than deferring the problem to runtime and
encountering a NullPointerException
. This helps to eliminate a common source of bugs
without paying the cost of wrappers like Optional
. Kotlin also allows using functional
constructs with nullable values as described in this
comprehensive guide to null-safety in Kotlin.
Although Java does not allow one to express null-safety in its type system, Spring Framework, Spring Data, and Reactor now provide null-safety of their API via tooling-friendly annotations. By default, types from Java APIs used in Kotlin are recognized as platform types for which null-checks are relaxed. Kotlin’s support for JSR 305 annotations combined with nullability annotations provide null-safety for the related Spring API in Kotlin.
The JSR 305 checks can be configured by adding the -Xjsr305
compiler flag with the
following options: -Xjsr305={strict|warn|ignore}
. The default behavior is the same as
-Xjsr305=warn
. The strict
value is required to have null-safety taken in account in
Kotlin types inferred from Spring API but should be used with the knowledge that Spring
API nullability declaration could evolve even between minor releases and more checks may
be added in the future).
Generic type arguments, varargs and array elements nullability are not yet supported. See SPR-15942 for up-to-date information. Also be aware that Spring Boot’s own API is not yet annotated. |
4.29.3. Kotlin API
runApplication
Spring Boot provides an idiomatic way to run an application with
runApplication<MyApplication>(*args)
as shown in the following example:
import org.springframework.boot.autoconfigure.SpringBootApplication
import org.springframework.boot.runApplication
@SpringBootApplication
class MyApplication
fun main(args: Array<String>) {
runApplication<MyApplication>(*args)
}
This is a drop-in replacement for
SpringApplication.run(MyApplication::class.java, *args)
. It also allows customization
of the application as shown in the following example:
runApplication<MyApplication>(*args) {
setBannerMode(OFF)
}
Extensions
Kotlin extensions provide the ability to extend existing classes with additional functionality. The Spring Boot Kotlin API makes use of these extensions to add new Kotlin specific conveniences to existing APIs.
TestRestTemplate
extensions, similar to those provided by Spring Framework for
RestOperations
in Spring Framework, are provided. Among other things, the extensions
make it possible to take advantage of Kotlin reified type parameters.
4.29.4. Dependency management
In order to avoid mixing different versions of Kotlin dependencies on the classpath, Spring Boot imports the Kotlin BOM.
With Maven, the Kotlin version can be customized via the kotlin.version
property and
plugin management is provided for kotlin-maven-plugin
. With Gradle, the Spring Boot
plugin automatically aligns the kotlin.version
with the version of the Kotlin plugin.
4.29.5. @ConfigurationProperties
@ConfigurationProperties
supports classes with immutable val
properties as shown in
the following example:
@ConfigurationProperties("example.kotlin")
data class KotlinExampleProperties(
val name: String,
val description: String,
val myService: MyService
)
data class MyService(
val apiToken: String,
val uri: URI
)
To generate your own
metadata using the annotation processor, kapt should
be configured with the spring-boot-configuration-processor dependency. Note that some
features (such as detecting the default value or deperecated items) are not working due
to limitations in the model kapt provides.
|
4.29.6. Testing
While it is possible to use JUnit 4 to test Kotlin code, JUnit 5 is recommended. JUnit 5
enables a test class to be instantiated once and reused for all of the class’s tests. This
makes it possible to use @BeforeClass
and @AfterClass
annotations on non-static
methods, which is a good fit for Kotlin.
JUnit 5 is the default and the vintage engine is provided for backward compatibility with
JUnit 4. If you don’t use it, exclude org.junit.vintange:junit-vintage-engine
. See the
JUnit 5 documentation
for more details. You also need to
switch test
instance lifecycle to "per-class".
To mock Kotlin classes, MockK is recommended. If you need the Mockk
equivalent of the Mockito specific
@MockBean
and @SpyBean
annotations, you can use SpringMockK which
provides similar @MockkBean
and @SpykBean
annotations.
4.29.7. Resources
Further reading
-
Kotlin Slack (with a dedicated #spring channel)
-
Tutorial: building web applications with Spring Boot and Kotlin
-
A Geospatial Messenger with Kotlin, Spring Boot and PostgreSQL
Examples
-
spring-boot-kotlin-demo: regular Spring Boot + Spring Data JPA project
-
mixit: Spring Boot 2 + WebFlux + Reactive Spring Data MongoDB
-
spring-kotlin-fullstack: WebFlux Kotlin fullstack example with Kotlin2js for frontend instead of JavaScript or TypeScript
-
spring-petclinic-kotlin: Kotlin version of the Spring PetClinic Sample Application
-
spring-kotlin-deepdive: a step by step migration for Boot 1.0 + Java to Boot 2.0 + Kotlin
4.30. What to Read Next
If you want to learn more about any of the classes discussed in this section, you can check out the Spring Boot API documentation or you can browse the source code directly. If you have specific questions, take a look at the how-to section.
If you are comfortable with Spring Boot’s core features, you can continue on and read about production-ready features.
5. Spring Boot Actuator: Production-ready Features
Spring Boot includes a number of additional features to help you monitor and manage your application when you push it to production. You can choose to manage and monitor your application by using HTTP endpoints or with JMX. Auditing, health, and metrics gathering can also be automatically applied to your application.
5.1. Enabling Production-ready Features
The spring-boot-actuator
module
provides all of Spring Boot’s production-ready features. The simplest way to enable the
features is to add a dependency to the spring-boot-starter-actuator
‘Starter’.
To add the actuator to a Maven based project, add the following ‘Starter’ dependency:
<dependencies>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-actuator</artifactId>
</dependency>
</dependencies>
For Gradle, use the following declaration:
dependencies {
compile("org.springframework.boot:spring-boot-starter-actuator")
}
5.2. Endpoints
Actuator endpoints let you monitor and interact with your application. Spring Boot
includes a number of built-in endpoints and lets you add your own. For example, the
health
endpoint provides basic application health information.
Each individual endpoint can be enabled
or disabled. This controls whether or not the endpoint is created and its bean exists in
the application context. To be remotely accessible an endpoint also has to be
exposed via JMX or HTTP. Most
applications choose HTTP, where the ID of the endpoint along with a prefix of /actuator
is mapped to a URL. For example, by default, the health
endpoint is mapped to
/actuator/health
.
The following technology-agnostic endpoints are available:
ID | Description | Enabled by default |
---|---|---|
|
Exposes audit events information for the current application. |
Yes |
|
Displays a complete list of all the Spring beans in your application. |
Yes |
|
Exposes available caches. |
Yes |
|
Shows the conditions that were evaluated on configuration and auto-configuration classes and the reasons why they did or did not match. |
Yes |
|
Displays a collated list of all |
Yes |
|
Exposes properties from Spring’s |
Yes |
|
Shows any Flyway database migrations that have been applied. |
Yes |
|
Shows application health information. |
Yes |
|
Displays HTTP trace information (by default, the last 100 HTTP request-response exchanges). |
Yes |
|
Displays arbitrary application info. |
Yes |
|
Shows the Spring Integration graph. |
Yes |
|
Shows and modifies the configuration of loggers in the application. |
Yes |
|
Shows any Liquibase database migrations that have been applied. |
Yes |
|
Shows ‘metrics’ information for the current application. |
Yes |
|
Displays a collated list of all |
Yes |
|
Displays the scheduled tasks in your application. |
Yes |
|
Allows retrieval and deletion of user sessions from a Spring Session-backed session store. Not available when using Spring Session’s support for reactive web applications. |
Yes |
|
Lets the application be gracefully shutdown. |
No |
|
Performs a thread dump. |
Yes |
If your application is a web application (Spring MVC, Spring WebFlux, or Jersey), you can use the following additional endpoints:
ID | Description | Enabled by default |
---|---|---|
|
Returns an |
Yes |
|
Exposes JMX beans over HTTP (when Jolokia is on the classpath, not available for WebFlux). |
Yes |
|
Returns the contents of the logfile (if |
Yes |
|
Exposes metrics in a format that can be scraped by a Prometheus server. |
Yes |
To learn more about the Actuator’s endpoints and their request and response formats, please refer to the separate API documentation (HTML or PDF).
5.2.1. Enabling Endpoints
By default, all endpoints except for shutdown
are enabled. To configure the enablement
of an endpoint, use its management.endpoint.<id>.enabled
property. The following
example enables the shutdown
endpoint:
management.endpoint.shutdown.enabled=true
If you prefer endpoint enablement to be opt-in rather than opt-out, set the
management.endpoints.enabled-by-default
property to false
and use individual endpoint
enabled
properties to opt back in. The following example enables the info
endpoint and
disables all other endpoints:
management.endpoints.enabled-by-default=false
management.endpoint.info.enabled=true
Disabled endpoints are removed entirely from the application context. If you want
to change only the technologies over which an endpoint is exposed, use the
include and exclude properties
instead.
|
5.2.2. Exposing Endpoints
Since Endpoints may contain sensitive information, careful consideration should be given about when to expose them. The following table shows the default exposure for the built-in endpoints:
ID | JMX | Web |
---|---|---|
|
Yes |
No |
|
Yes |
No |
|
Yes |
No |
|
Yes |
No |
|
Yes |
No |
|
Yes |
No |
|
Yes |
No |
|
Yes |
Yes |
|
N/A |
No |
|
Yes |
No |
|
Yes |
Yes |
|
Yes |
No |
|
N/A |
No |
|
N/A |
No |
|
Yes |
No |
|
Yes |
No |
|
Yes |
No |
|
Yes |
No |
|
N/A |
No |
|
Yes |
No |
|
Yes |
No |
|
Yes |
No |
|
Yes |
No |
To change which endpoints are exposed, use the following technology-specific include
and
exclude
properties:
Property | Default |
---|---|
|
|
|
|
|
|
|
|
The include
property lists the IDs of the endpoints that are exposed. The exclude
property lists the IDs of the endpoints that should not be exposed. The exclude
property takes precedence over the include
property. Both include
and exclude
properties can be configured with a list of endpoint IDs.
For example, to stop exposing all endpoints over JMX and only expose the health
and
info
endpoints, use the following property:
management.endpoints.jmx.exposure.include=health,info
*
can be used to select all endpoints. For example, to expose everything over HTTP
except the env
and beans
endpoints, use the following properties:
management.endpoints.web.exposure.include=*
management.endpoints.web.exposure.exclude=env,beans
|
If your application is exposed publicly, we strongly recommend that you also secure your endpoints. |
If you want to implement your own strategy for when endpoints are exposed, you can
register an EndpointFilter bean.
|
5.2.3. Securing HTTP Endpoints
You should take care to secure HTTP endpoints in the same way that you would any other
sensitive URL. If Spring Security is present, endpoints are secured by default using
Spring Security’s content-negotiation strategy. If you wish to configure custom security
for HTTP endpoints, for example, only allow users with a certain role to access them,
Spring Boot provides some convenient RequestMatcher
objects that can be used in
combination with Spring Security.
A typical Spring Security configuration might look something like the following example:
@Configuration(proxyBeanMethods = false)
public class ActuatorSecurity extends WebSecurityConfigurerAdapter {
@Override
protected void configure(HttpSecurity http) throws Exception {
http.requestMatcher(EndpointRequest.toAnyEndpoint()).authorizeRequests((requests) ->
requests.anyRequest().hasRole("ENDPOINT_ADMIN"));
http.httpBasic();
}
}
The preceding example uses EndpointRequest.toAnyEndpoint()
to match a request to any
endpoint and then ensures that all have the ENDPOINT_ADMIN
role. Several other matcher
methods are also available on EndpointRequest
. See the API documentation
(HTML or
PDF) for details.
If you deploy applications behind a firewall, you may prefer that all your actuator
endpoints can be accessed without requiring authentication. You can do so by changing the
management.endpoints.web.exposure.include
property, as follows:
management.endpoints.web.exposure.include=*
Additionally, if Spring Security is present, you would need to add custom security configuration that allows unauthenticated access to the endpoints as shown in the following example:
@Configuration(proxyBeanMethods = false)
public class ActuatorSecurity extends WebSecurityConfigurerAdapter {
@Override
protected void configure(HttpSecurity http) throws Exception {
http.requestMatcher(EndpointRequest.toAnyEndpoint()).authorizeRequests((requests) ->
requests.anyRequest().permitAll());
}
}
5.2.4. Configuring Endpoints
Endpoints automatically cache responses to read operations that do not take any
parameters. To configure the amount of time for which an endpoint will cache a response,
use its cache.time-to-live
property. The following example sets the time-to-live of
the beans
endpoint’s cache to 10 seconds:
management.endpoint.beans.cache.time-to-live=10s
The prefix management.endpoint.<name> is used to uniquely identify the
endpoint that is being configured.
|
When making an authenticated HTTP request, the Principal is considered as input to
the endpoint and, therefore, the response will not be cached.
|
5.2.5. Hypermedia for Actuator Web Endpoints
A “discovery page” is added with links to all the endpoints. The “discovery page” is
available on /actuator
by default.
When a custom management context path is configured, the “discovery page” automatically
moves from /actuator
to the root of the management context. For example, if the
management context path is /management
, then the discovery page is available from
/management
. When the management context path is set to /
, the discovery page is
disabled to prevent the possibility of a clash with other mappings.
5.2.6. CORS Support
Cross-origin resource sharing (CORS) is a W3C specification that lets you specify in a flexible way what kind of cross-domain requests are authorized. If you use Spring MVC or Spring WebFlux, Actuator’s web endpoints can be configured to support such scenarios.
CORS support is disabled by default and is only enabled once the
management.endpoints.web.cors.allowed-origins
property has been set. The following
configuration permits GET
and POST
calls from the example.com
domain:
management.endpoints.web.cors.allowed-origins=https://example.com
management.endpoints.web.cors.allowed-methods=GET,POST
See CorsEndpointProperties for a complete list of options. |
5.2.7. Implementing Custom Endpoints
If you add a @Bean
annotated with @Endpoint
, any methods annotated with
@ReadOperation
, @WriteOperation
, or @DeleteOperation
are automatically exposed over
JMX and, in a web application, over HTTP as well. Endpoints can be exposed over HTTP using
Jersey, Spring MVC, or Spring WebFlux.
You can also write technology-specific endpoints by using @JmxEndpoint
or
@WebEndpoint
. These endpoints are restricted to their respective technologies. For
example, @WebEndpoint
is exposed only over HTTP and not over JMX.
You can write technology-specific extensions by using @EndpointWebExtension
and
@EndpointJmxExtension
. These annotations let you provide technology-specific operations
to augment an existing endpoint.
Finally, if you need access to web-framework-specific functionality, you can implement
Servlet or Spring @Controller
and @RestController
endpoints at the cost of them not
being available over JMX or when using a different web framework.
Receiving Input
Operations on an endpoint receive input via their parameters. When exposed via the web,
the values for these parameters are taken from the URL’s query parameters and from the
JSON request body. When exposed via JMX, the parameters are mapped to the parameters of
the MBean’s operations. Parameters are required by default. They can be made optional
by annotating them with @org.springframework.lang.Nullable
.
Each root property in the JSON request body can be mapped to a parameter of the endpoint. Consider the following JSON request body:
{
"name": "test",
"counter": 42
}
This can be used to invoke a write operation that takes String name
and int counter
parameters.
Because endpoints are technology agnostic, only simple types can be specified in the
method signature. In particular declaring a single parameter with a custom type defining a
name and counter properties is not supported.
|
To allow the input to be mapped to the operation method’s parameters, Java code
implementing an endpoint should be compiled with -parameters , and Kotlin code
implementing an endpoint should be compiled with -java-parameters . This will happen
automatically if you are using Spring Boot’s Gradle plugin or if you are using Maven and
spring-boot-starter-parent .
|
Input type conversion
The parameters passed to endpoint operation methods are, if necessary, automatically
converted to the required type. Before calling an operation method, the input received via
JMX or an HTTP request is converted to the required types using an instance of
ApplicationConversionService
as well as any Converter
or GenericConverter
beans
qualified with @EndpointConverter
.
Custom Web Endpoints
Operations on an @Endpoint
, @WebEndpoint
, or @EndpointWebExtension
are automatically
exposed over HTTP using Jersey, Spring MVC, or Spring WebFlux.
Web Endpoint Request Predicates
A request predicate is automatically generated for each operation on a web-exposed endpoint.
Path
The path of the predicate is determined by the ID of the endpoint and the base path of
web-exposed endpoints. The default base path is /actuator
. For example, an endpoint with
the ID sessions
will use /actuator/sessions
as its path in the predicate.
The path can be further customized by annotating one or more parameters of the operation
method with @Selector
. Such a parameter is added to the path predicate as a path
variable. The variable’s value is passed into the operation method when the endpoint
operation is invoked. If you want to capture all remaining path elements, you can add
@Selector(Match=ALL_REMAINING)
to the last parameter and make it a type that is
conversion compatible with a String[]
.
HTTP method
The HTTP method of the predicate is determined by the operation type, as shown in the following table:
Operation | HTTP method |
---|---|
|
|
|
|
|
|
Consumes
For a @WriteOperation
(HTTP POST
) that uses the request body, the consumes clause of
the predicate is application/vnd.spring-boot.actuator.v2+json, application/json
. For
all other operations the consumes clause is empty.
Produces
The produces clause of the predicate can be determined by the produces
attribute of the
@DeleteOperation
, @ReadOperation
, and @WriteOperation
annotations. The attribute is
optional. If it is not used, the produces clause is determined automatically.
If the operation method returns void
or Void
the produces clause is empty. If the
operation method returns a org.springframework.core.io.Resource
, the produces clause is
application/octet-stream
. For all other operations the produces clause is
application/vnd.spring-boot.actuator.v2+json, application/json
.
Web Endpoint Response Status
The default response status for an endpoint operation depends on the operation type (read, write, or delete) and what, if anything, the operation returns.
A @ReadOperation
returns a value, the response status will be 200 (OK). If it does not
return a value, the response status will be 404 (Not Found).
If a @WriteOperation
or @DeleteOperation
returns a value, the response status will be
200 (OK). If it does not return a value the response status will be 204 (No Content).
If an operation is invoked without a required parameter, or with a parameter that cannot be converted to the required type, the operation method will not be called and the response status will be 400 (Bad Request).
Web Endpoint Range Requests
An HTTP range request can be used to request part of an HTTP resource. When using Spring
MVC or Spring Web Flux, operations that return a org.springframework.core.io.Resource
automatically support range requests.
Range requests are not supported when using Jersey. |
Web Endpoint Security
An operation on a web endpoint or a web-specific endpoint extension can receive the
current java.security.Principal
or
org.springframework.boot.actuate.endpoint.SecurityContext
as a method parameter. The
former is typically used in conjunction with @Nullable
to provide different behaviour
for authenticated and unauthenticated users. The latter is typically used to perform
authorization checks using its isUserInRole(String)
method.
Servlet endpoints
A Servlet
can be exposed as an endpoint by implementing a class annotated with
@ServletEndpoint
that also implements Supplier<EndpointServlet>
. Servlet endpoints
provide deeper integration with the Servlet container but at the expense of portability.
They are intended to be used to expose an existing Servlet
as an endpoint. For new
endpoints, the @Endpoint
and @WebEndpoint
annotations should be preferred whenever
possible.
Controller endpoints
@ControllerEndpoint
and @RestControllerEndpoint
can be used to implement an endpoint
that is only exposed by Spring MVC or Spring WebFlux. Methods are mapped using the
standard annotations for Spring MVC and Spring WebFlux such as @RequestMapping
and @GetMapping
, with the endpoint’s ID being used as a prefix for the path. Controller
endpoints provide deeper integration with Spring’s web frameworks but at the expense of
portability. The @Endpoint
and @WebEndpoint
annotations should be preferred whenever
possible.
5.2.8. Health Information
You can use health information to check the status of your running application. It is
often used by monitoring software to alert someone when a production system goes down.
The information exposed by the health
endpoint depends on the
management.endpoint.health.show-details
property which can be configured with one of the
following values:
Name | Description |
---|---|
|
Details are never shown. |
|
Details are only shown to authorized users. Authorized roles can be configured using
|
|
Details are shown to all users. |
The default value is never
. A user is considered to be authorized when they
are in one or more of the endpoint’s roles. If the endpoint has no configured roles
(the default) all authenticated users are considered to be authorized. The roles can
be configured using the management.endpoint.health.roles
property.
If you have secured your application and wish to use always , your security
configuration must permit access to the health endpoint for both authenticated and
unauthenticated users.
|
Health information is collected from the content of a
HealthIndicatorRegistry
(by default all
HealthIndicator
instances
defined in your ApplicationContext
. Spring Boot includes a number of auto-configured
HealthIndicators
and you can also write your own. By default, the final system state is
derived by the HealthAggregator
which sorts the statuses from each HealthIndicator
based on an ordered list of statuses. The first status in the sorted list is used as the
overall health status. If no HealthIndicator
returns a status that is known to the
HealthAggregator
, an UNKNOWN
status is used.
The HealthIndicatorRegistry can be used to register and unregister health
indicators at runtime.
|
Auto-configured HealthIndicators
The following HealthIndicators
are auto-configured by Spring Boot when appropriate:
Name | Description |
---|---|
Checks that a Cassandra database is up. |
|
Checks that a Couchbase cluster is up. |
|
Checks for low disk space. |
|
Checks that a connection to |
|
Checks that an Elasticsearch cluster is up. |
|
Checks that an Hazelcast server is up. |
|
Checks that an InfluxDB server is up. |
|
Checks that a JMS broker is up. |
|
Checks that a mail server is up. |
|
Checks that a Mongo database is up. |
|
Checks that a Neo4j server is up. |
|
Checks that a Rabbit server is up. |
|
Checks that a Redis server is up. |
|
Checks that a Solr server is up. |
You can disable them all by setting the management.health.defaults.enabled
property.
|
Writing Custom HealthIndicators
To provide custom health information, you can register Spring beans that implement the
HealthIndicator
interface.
You need to provide an implementation of the health()
method and return a Health
response. The Health
response should include a status and can optionally include
additional details to be displayed. The following code shows a sample HealthIndicator
implementation:
import org.springframework.boot.actuate.health.Health;
import org.springframework.boot.actuate.health.HealthIndicator;
import org.springframework.stereotype.Component;
@Component
public class MyHealthIndicator implements HealthIndicator {
@Override
public Health health() {
int errorCode = check(); // perform some specific health check
if (errorCode != 0) {
return Health.down().withDetail("Error Code", errorCode).build();
}
return Health.up().build();
}
}
The identifier for a given HealthIndicator is the name of the bean without the
HealthIndicator suffix, if it exists. In the preceding example, the health information
is available in an entry named my .
|
In addition to Spring Boot’s predefined
Status
types, it is also possible for
Health
to return a custom Status
that represents a new system state. In such cases, a
custom implementation of the
HealthAggregator
interface
also needs to be provided, or the default implementation has to be configured by using
the management.health.status.order
configuration property.
For example, assume a new Status
with code FATAL
is being used in one of your
HealthIndicator
implementations. To configure the severity order, add the following
property to your application properties:
management.health.status.order=FATAL, DOWN, OUT_OF_SERVICE, UNKNOWN, UP
The HTTP status code in the response reflects the overall health status (for example,
UP
maps to 200, while OUT_OF_SERVICE
and DOWN
map to 503). You might also want to
register custom status mappings if you access the health endpoint over HTTP. For example,
the following property maps FATAL
to 503 (service unavailable):
management.health.status.http-mapping.FATAL=503
If you need more control, you can define your own HealthStatusHttpMapper bean.
|
The following table shows the default status mappings for the built-in statuses:
Status | Mapping |
---|---|
DOWN |
SERVICE_UNAVAILABLE (503) |
OUT_OF_SERVICE |
SERVICE_UNAVAILABLE (503) |
UP |
No mapping by default, so http status is 200 |
UNKNOWN |
No mapping by default, so http status is 200 |
Reactive Health Indicators
For reactive applications, such as those using Spring WebFlux, ReactiveHealthIndicator
provides a non-blocking contract for getting application health. Similar to a traditional
HealthIndicator
, health information is collected from the content of a
ReactiveHealthIndicatorRegistry
(by default all
HealthIndicator
and
ReactiveHealthIndicator
instances defined in your ApplicationContext
. Regular
HealthIndicator
that do not check against a reactive API are executed on the elastic
scheduler.
In a reactive application, The ReactiveHealthIndicatorRegistry can be used to
register and unregister health indicators at runtime.
|
To provide custom health information from a reactive API, you can register Spring beans
that implement the
ReactiveHealthIndicator
interface. The following code shows a sample ReactiveHealthIndicator
implementation:
@Component
public class MyReactiveHealthIndicator implements ReactiveHealthIndicator {
@Override
public Mono<Health> health() {
return doHealthCheck() //perform some specific health check that returns a Mono<Health>
.onErrorResume(ex -> Mono.just(new Health.Builder().down(ex).build())));
}
}
To handle the error automatically, consider extending from
AbstractReactiveHealthIndicator .
|
Auto-configured ReactiveHealthIndicators
The following ReactiveHealthIndicators
are auto-configured by Spring Boot when
appropriate:
Name | Description |
---|---|
Checks that a Cassandra database is up. |
|
Checks that a Couchbase cluster is up. |
|
Checks that a Mongo database is up. |
|
Checks that a Redis server is up. |
If necessary, reactive indicators replace the regular ones. Also, any
HealthIndicator that is not handled explicitly is wrapped automatically.
|
5.2.9. Application Information
Application information exposes various information collected from all
InfoContributor
beans defined
in your ApplicationContext
. Spring Boot includes a number of auto-configured
InfoContributor
beans, and you can write your own.
Auto-configured InfoContributors
The following InfoContributor
beans are auto-configured by Spring Boot, when
appropriate:
Name | Description |
---|---|
Exposes any key from the |
|
Exposes git information if a |
|
Exposes build information if a |
It is possible to disable them all by setting the management.info.defaults.enabled
property.
|
Custom Application Information
You can customize the data exposed by the info
endpoint by setting info.*
Spring
properties. All Environment
properties under the info
key are automatically exposed.
For example, you could add the following settings to your application.properties
file:
info.app.encoding=UTF-8
info.app.java.source=1.8
info.app.java.target=1.8
Rather than hardcoding those values, you could also expand info properties at build time. Assuming you use Maven, you could rewrite the preceding example as follows: |
Git Commit Information
Another useful feature of the info
endpoint is its ability to publish information about
the state of your git
source code repository when the project was built. If a
GitProperties
bean is available, the git.branch
, git.commit.id
, and
git.commit.time
properties are exposed.
A GitProperties bean is auto-configured if a git.properties file is available at
the root of the classpath. See
"Generate git information" for more details.
|
If you want to display the full git information (that is, the full content of
git.properties
), use the management.info.git.mode
property, as follows:
management.info.git.mode=full
Build Information
If a BuildProperties
bean is available, the info
endpoint can also publish
information about your build. This happens if a META-INF/build-info.properties
file is
available in the classpath.
The Maven and Gradle plugins can both generate that file. See "Generate build information" for more details. |
Writing Custom InfoContributors
To provide custom application information, you can register Spring beans that implement
the InfoContributor
interface.
The following example contributes an example
entry with a single value:
import java.util.Collections;
import org.springframework.boot.actuate.info.Info;
import org.springframework.boot.actuate.info.InfoContributor;
import org.springframework.stereotype.Component;
@Component
public class ExampleInfoContributor implements InfoContributor {
@Override
public void contribute(Info.Builder builder) {
builder.withDetail("example",
Collections.singletonMap("key", "value"));
}
}
If you reach the info
endpoint, you should see a response that contains the following
additional entry:
{
"example": {
"key" : "value"
}
}
5.3. Monitoring and Management over HTTP
If you are developing a web application, Spring Boot Actuator auto-configures all
enabled endpoints to be exposed over HTTP. The default convention is to use the id
of
the endpoint with a prefix of /actuator
as the URL path. For example, health
is
exposed as /actuator/health
.
TIP: Actuator is supported natively with Spring MVC, Spring WebFlux, and Jersey.
5.3.1. Customizing the Management Endpoint Paths
Sometimes, it is useful to customize the prefix for the management endpoints. For
example, your application might already use /actuator
for another purpose. You can
use the management.endpoints.web.base-path
property to change the prefix for your
management endpoint, as shown in the following example:
management.endpoints.web.base-path=/manage
The preceding application.properties
example changes the endpoint from
/actuator/{id}
to /manage/{id}
(for example, /manage/info
).
Unless the management port has been configured to
expose endpoints by using a
different HTTP port, management.endpoints.web.base-path is relative to
server.servlet.context-path . If management.server.port is configured,
management.endpoints.web.base-path is relative to
management.server.servlet.context-path .
|
If you want to map endpoints to a different path, you can use the
management.endpoints.web.path-mapping
property.
The following example remaps /actuator/health
to /healthcheck
:
management.endpoints.web.base-path=/
management.endpoints.web.path-mapping.health=healthcheck
5.3.2. Customizing the Management Server Port
Exposing management endpoints by using the default HTTP port is a sensible choice for cloud-based deployments. If, however, your application runs inside your own data center, you may prefer to expose endpoints by using a different HTTP port.
You can set the management.server.port
property to change the HTTP port, as shown in
the following example:
management.server.port=8081
On Cloud Foundry, applications only receive requests on port 8080 for both HTTP and TCP routing, by default. If you want to use a custom management port on Cloud Foundry, you will need to explicitly set up the application’s routes to forward traffic to the custom port. |
5.3.3. Configuring Management-specific SSL
When configured to use a custom port, the management server can also be configured with
its own SSL by using the various management.server.ssl.*
properties. For example, doing
so lets a management server be available over HTTP while the main application uses HTTPS,
as shown in the following property settings:
server.port=8443
server.ssl.enabled=true
server.ssl.key-store=classpath:store.jks
server.ssl.key-password=secret
management.server.port=8080
management.server.ssl.enabled=false
Alternatively, both the main server and the management server can use SSL but with different key stores, as follows:
server.port=8443
server.ssl.enabled=true
server.ssl.key-store=classpath:main.jks
server.ssl.key-password=secret
management.server.port=8080
management.server.ssl.enabled=true
management.server.ssl.key-store=classpath:management.jks
management.server.ssl.key-password=secret
5.3.4. Customizing the Management Server Address
You can customize the address that the management endpoints are available on by setting
the management.server.address
property. Doing so can be useful if you want to listen
only on an internal or ops-facing network or to listen only for connections from
localhost
.
You can listen on a different address only when the port differs from the main server port. |
The following example application.properties
does not allow remote management
connections:
management.server.port=8081
management.server.address=127.0.0.1
5.3.5. Disabling HTTP Endpoints
If you do not want to expose endpoints over HTTP, you can set the management port to
-1
, as shown in the following example:
management.server.port=-1
This can be achieved using the management.endpoints.web.exposure.exclude
property as well, as shown in
following example:
management.endpoints.web.exposure.exclude=*
5.4. Monitoring and Management over JMX
Java Management Extensions (JMX) provide a standard mechanism to monitor and manage
applications. By default, this feature is not enabled and can be turned on with
the configuration property spring.jmx.enabled=true
. Spring Boot exposes
management endpoints as JMX MBeans under the org.springframework.boot
domain by default.
5.4.1. Customizing MBean Names
The name of the MBean is usually generated from the id
of the endpoint. For example, the
health
endpoint is exposed as org.springframework.boot:type=Endpoint,name=Health
.
If your application contains more than one Spring ApplicationContext
, you may find that
names clash. To solve this problem, you can set the spring.jmx.unique-names
property to
true
so that MBean names are always unique.
You can also customize the JMX domain under which endpoints are exposed. The following
settings show an example of doing so in application.properties
:
spring.jmx.unique-names=true
management.endpoints.jmx.domain=com.example.myapp
5.4.2. Disabling JMX Endpoints
If you do not want to expose endpoints over JMX, you can set the
management.endpoints.jmx.exposure.exclude
property to *
, as shown in the following
example:
management.endpoints.jmx.exposure.exclude=*
5.4.3. Using Jolokia for JMX over HTTP
Jolokia is a JMX-HTTP bridge that provides an alternative method of accessing JMX beans.
To use Jolokia, include a dependency to org.jolokia:jolokia-core
. For example, with
Maven, you would add the following dependency:
<dependency>
<groupId>org.jolokia</groupId>
<artifactId>jolokia-core</artifactId>
</dependency>
The Jolokia endpoint can then be exposed by adding jolokia
or *
to the
management.endpoints.web.exposure.include
property. You can then access it by using
/actuator/jolokia
on your management HTTP server.
Customizing Jolokia
Jolokia has a number of settings that you would traditionally configure by setting servlet
parameters. With Spring Boot, you can use your application.properties
file. To do so,
prefix the parameter with management.endpoint.jolokia.config.
, as shown in the following
example:
management.endpoint.jolokia.config.debug=true
5.5. Loggers
Spring Boot Actuator includes the ability to view and configure the log levels of your application at runtime. You can view either the entire list or an individual logger’s configuration, which is made up of both the explicitly configured logging level as well as the effective logging level given to it by the logging framework. These levels can be one of:
-
TRACE
-
DEBUG
-
INFO
-
WARN
-
ERROR
-
FATAL
-
OFF
-
null
null
indicates that there is no explicit configuration.
5.5.1. Configure a Logger
To configure a given logger, POST
a partial entity to the resource’s URI, as shown in
the following example:
{
"configuredLevel": "DEBUG"
}
To “reset” the specific level of the logger (and use the default configuration
instead), you can pass a value of null as the configuredLevel .
|
5.6. Metrics
Spring Boot Actuator provides dependency management and auto-configuration for Micrometer, an application metrics facade that supports numerous monitoring systems, including:
To learn more about Micrometer’s capabilities, please refer to its reference documentation, in particular the concepts section. |
5.6.1. Getting started
Spring Boot auto-configures a composite MeterRegistry
and adds a registry to the
composite for each of the supported implementations that it finds on the classpath. Having
a dependency on micrometer-registry-{system}
in your runtime classpath is enough for
Spring Boot to configure the registry.
Most registries share common features. For instance, you can disable a particular registry even if the Micrometer registry implementation is on the classpath. For instance, to disable Datadog:
management.metrics.export.datadog.enabled=false
Spring Boot will also add any auto-configured registries to the global static composite
registry on the Metrics
class unless you explicitly tell it not to:
management.metrics.use-global-registry=false
You can register any number of MeterRegistryCustomizer
beans to further configure the
registry, such as applying common tags, before any meters are registered with the
registry:
@Bean
MeterRegistryCustomizer<MeterRegistry> metricsCommonTags() {
return registry -> registry.config().commonTags("region", "us-east-1");
}
You can apply customizations to particular registry implementations by being more specific about the generic type:
@Bean
MeterRegistryCustomizer<GraphiteMeterRegistry> graphiteMetricsNamingConvention() {
return registry -> registry.config().namingConvention(MY_CUSTOM_CONVENTION);
}
With that setup in place you can inject MeterRegistry
in your components and register
metrics:
@Component
public class SampleBean {
private final Counter counter;
public SampleBean(MeterRegistry registry) {
this.counter = registry.counter("received.messages");
}
public void handleMessage(String message) {
this.counter.increment();
// handle message implementation
}
}
Spring Boot also configures built-in instrumentation
(i.e. MeterBinder
implementations) that you can control via configuration or dedicated
annotation markers.
5.6.2. Supported monitoring systems
AppOptics
By default, the AppOptics registry pushes metrics to api.appoptics.com/v1/measurements periodically. To export metrics to SaaS AppOptics, your API token must be provided:
management.metrics.export.appoptics.api-token=YOUR_TOKEN
Atlas
By default, metrics are exported to Atlas running on your local machine. The location of the Atlas server to use can be provided using:
management.metrics.export.atlas.uri=https://atlas.example.com:7101/api/v1/publish
Datadog
Datadog registry pushes metrics to datadoghq periodically. To export metrics to Datadog, your API key must be provided:
management.metrics.export.datadog.api-key=YOUR_KEY
You can also change the interval at which metrics are sent to Datadog:
management.metrics.export.datadog.step=30s
Dynatrace
Dynatrace registry pushes metrics to the configured URI periodically. To export metrics to Dynatrace, your API token, device ID, and URI must be provided:
management.metrics.export.dynatrace.api-token=YOUR_TOKEN
management.metrics.export.dynatrace.device-id=YOUR_DEVICE_ID
management.metrics.export.dynatrace.uri=YOUR_URI
You can also change the interval at which metrics are sent to Dynatrace:
management.metrics.export.dynatrace.step=30s
Elastic
By default, metrics are exported to Elastic running on your local machine. The location of the Elastic server to use can be provided using the following property:
management.metrics.export.elastic.host=https://elastic.example.com:8086
Ganglia
By default, metrics are exported to Ganglia running on your local machine. The Ganglia server host and port to use can be provided using:
management.metrics.export.ganglia.host=ganglia.example.com
management.metrics.export.ganglia.port=9649
Graphite
By default, metrics are exported to Graphite running on your local machine. The Graphite server host and port to use can be provided using:
management.metrics.export.graphite.host=graphite.example.com
management.metrics.export.graphite.port=9004
Micrometer provides a default HierarchicalNameMapper
that governs how a dimensional
meter id is mapped
to flat hierarchical names.
To take control over this behaviour, define your GraphiteMeterRegistry and supply
your own HierarchicalNameMapper . An auto-configured GraphiteConfig and Clock beans
are provided unless you define your own:
|
@Bean
public GraphiteMeterRegistry graphiteMeterRegistry(GraphiteConfig config, Clock clock) {
return new GraphiteMeterRegistry(config, clock, MY_HIERARCHICAL_MAPPER);
}
Humio
By default, the Humio registry pushes metrics to cloud.humio.com periodically. To export metrics to SaaS Humio, your API token must be provided:
management.metrics.export.humio.api-token=YOUR_TOKEN
You should also configure one or more tags to identify the data source to which metrics will be pushed:
management.metrics.export.humio.tags.alpha=a
management.metrics.export.humio.tags.bravo=b
Influx
By default, metrics are exported to Influx running on your local machine. The location of the Influx server to use can be provided using:
management.metrics.export.influx.uri=https://influx.example.com:8086
JMX
Micrometer provides a hierarchical mapping to
JMX, primarily as a cheap and portable way to
view metrics locally. By default, metrics are exported to the metrics
JMX domain. The
domain to use can be provided using:
management.metrics.export.jmx.domain=com.example.app.metrics
Micrometer provides a default HierarchicalNameMapper
that governs how a dimensional
meter id is mapped to
flat hierarchical names.
To take control over this behaviour, define your JmxMeterRegistry and supply your
own HierarchicalNameMapper . An auto-configured JmxConfig and Clock beans are
provided unless you define your own:
|
@Bean
public JmxMeterRegistry jmxMeterRegistry(JmxConfig config, Clock clock) {
return new JmxMeterRegistry(config, clock, MY_HIERARCHICAL_MAPPER);
}
KairosDB
By default, metrics are exported to KairosDB running on your local machine. The location of the KairosDB server to use can be provided using:
management.metrics.export.kairos.uri=https://kairosdb.example.com:8080/api/v1/datapoints
New Relic
New Relic registry pushes metrics to New Relic periodically. To export metrics to New Relic, your API key and account id must be provided:
management.metrics.export.newrelic.api-key=YOUR_KEY
management.metrics.export.newrelic.account-id=YOUR_ACCOUNT_ID
You can also change the interval at which metrics are sent to New Relic:
management.metrics.export.newrelic.step=30s
Prometheus
Prometheus expects to scrape or poll
individual app instances for metrics. Spring Boot provides an actuator endpoint available
at /actuator/prometheus
to present a Prometheus scrape with the
appropriate format.
The endpoint is not available by default and must be exposed, see exposing endpoints for more details. |
Here is an example scrape_config
to add to prometheus.yml
:
scrape_configs:
- job_name: 'spring'
metrics_path: '/actuator/prometheus'
static_configs:
- targets: ['HOST:PORT']
SignalFx
SignalFx registry pushes metrics to SignalFx periodically. To export metrics to SignalFx, your access token must be provided:
management.metrics.export.signalfx.access-token=YOUR_ACCESS_TOKEN
You can also change the interval at which metrics are sent to SignalFx:
management.metrics.export.signalfx.step=30s
Simple
Micrometer ships with a simple, in-memory backend that is automatically used as a fallback if no other registry is configured. This allows you to see what metrics are collected in the metrics endpoint.
The in-memory backend disables itself as soon as you’re using any of the other available backend. You can also disable it explicitly:
management.metrics.export.simple.enabled=false
StatsD
The StatsD registry pushes metrics over UDP to a StatsD agent eagerly. By default, metrics are exported to a StatsD agent running on your local machine. The StatsD agent host and port to use can be provided using:
management.metrics.export.statsd.host=statsd.example.com
management.metrics.export.statsd.port=9125
You can also change the StatsD line protocol to use (default to Datadog):
management.metrics.export.statsd.flavor=etsy
Wavefront
Wavefront registry pushes metrics to Wavefront periodically. If you are exporting metrics to Wavefront directly, your API token must be provided:
management.metrics.export.wavefront.api-token=YOUR_API_TOKEN
Alternatively, you may use a Wavefront sidecar or an internal proxy set up in your environment that forwards metrics data to the Wavefront API host:
management.metrics.export.wavefront.uri=proxy://localhost:2878
If publishing metrics to a Wavefront proxy (as described in
the documentation), the host must be
in the proxy://HOST:PORT format.
|
You can also change the interval at which metrics are sent to Wavefront:
management.metrics.export.wavefront.step=30s
5.6.3. Supported Metrics
Spring Boot registers the following core metrics when applicable:
-
JVM metrics, report utilization of:
-
Various memory and buffer pools
-
Statistics related to garbage collection
-
Threads utilization
-
Number of classes loaded/unloaded
-
-
CPU metrics
-
File descriptor metrics
-
Kafka consumer metrics
-
Log4j2 metrics: record the number of events logged to Log4j2 at each level
-
Logback metrics: record the number of events logged to Logback at each level
-
Uptime metrics: report a gauge for uptime and a fixed gauge representing the application’s absolute start time
-
Tomcat metrics (
server.tomcat.mbeanregistry.enabled
must be set totrue
for all Tomcat metrics to be registered) -
Spring Integration metrics
Spring MVC Metrics
Auto-configuration enables the instrumentation of requests handled by Spring MVC. When
management.metrics.web.server.request.autotime.enabled
is true
, this instrumentation
occurs for all requests. Alternatively, when set to false
, you can enable
instrumentation by adding @Timed
to a request-handling method:
@RestController
@Timed (1)
public class MyController {
@GetMapping("/api/people")
@Timed(extraTags = { "region", "us-east-1" }) (2)
@Timed(value = "all.people", longTask = true) (3)
public List<Person> listPeople() { ... }
}
1 | A controller class to enable timings on every request handler in the controller. |
2 | A method to enable for an individual endpoint. This is not necessary if you have it on the class, but can be used to further customize the timer for this particular endpoint. |
3 | A method with longTask = true to enable a long task timer for the method. Long task
timers require a separate metric name, and can be stacked with a short task timer. |
By default, metrics are generated with the name, http.server.requests
. The name can be
customized by setting the management.metrics.web.server.requests-metric-name
property.
By default, Spring MVC-related metrics are tagged with the following information:
Tag | Description |
---|---|
|
Simple class name of any exception that was thrown while handling the request. |
|
Request’s method (for example, |
|
Request’s outcome based on the status code of the response. 1xx is
|
|
Response’s HTTP status code (for example, |
|
Request’s URI template prior to variable substitution, if possible (for example,
|
To customize the tags, provide a @Bean
that implements WebMvcTagsProvider
.
Spring WebFlux Metrics
Auto-configuration enables the instrumentation of all requests handled by WebFlux controllers and functional handlers.
By default, metrics are generated with the name http.server.requests
. You can customize
the name by setting the management.metrics.web.server.requests-metric-name
property.
By default, WebFlux-related metrics are tagged with the following information:
Tag | Description |
---|---|
|
Simple class name of any exception that was thrown while handling the request. |
|
Request’s method (for example, |
|
Request’s outcome based on the status code of the response. 1xx is
|
|
Response’s HTTP status code (for example, |
|
Request’s URI template prior to variable substitution, if possible (for example,
|
To customize the tags, provide a @Bean
that implements WebFluxTagsProvider
.
Jersey Server Metrics
Auto-configuration enables the instrumentation of requests handled by the Jersey JAX-RS
implementation. When management.metrics.web.server.request.autotime.enabled
is true
,
this instrumentation occurs for all requests. Alternatively, when set to false
, you can
enable instrumentation by adding @Timed
to a request-handling method:
@Component
@Path("/api/people")
@Timed (1)
public class Endpoint {
@GET
@Timed(extraTags = { "region", "us-east-1" }) (2)
@Timed(value = "all.people", longTask = true) (3)
public List<Person> listPeople() { ... }
}
1 | On a resource class to enable timings on every request handler in the resource. |
2 | On a method to enable for an individual endpoint. This is not necessary if you have it on the class, but can be used to further customize the timer for this particular endpoint. |
3 | On a method with longTask = true to enable a long task timer for the method. Long task
timers require a separate metric name, and can be stacked with a short task timer. |
By default, metrics are generated with the name, http.server.requests
. The name can be
customized by setting the management.metrics.web.server.requests-metric-name
property.
By default, Jersey server metrics are tagged with the following information:
Tag | Description |
---|---|
|
Simple class name of any exception that was thrown while handling the request. |
|
Request’s method (for example, |
|
Request’s outcome based on the status code of the response. 1xx is
|
|
Response’s HTTP status code (for example, |
|
Request’s URI template prior to variable substitution, if possible (for example,
|
To customize the tags, provide a @Bean
that implements JerseyTagsProvider
.
HTTP Client Metrics
Spring Boot Actuator manages the instrumentation of both RestTemplate
and WebClient
.
For that, you have to get injected with an auto-configured builder
and use it to create instances:
-
RestTemplateBuilder
forRestTemplate
-
WebClient.Builder
forWebClient
It is also possible to apply manually the customizers responsible for this instrumentation,
namely MetricsRestTemplateCustomizer
and MetricsWebClientCustomizer
.
By default, metrics are generated with the name, http.client.requests
. The name can be
customized by setting the management.metrics.web.client.requests-metric-name
property.
By default, metrics generated by an instrumented client are tagged with the following information:
Tag | Description |
---|---|
|
Host portion of the URI |
|
Request’s method (for example, |
|
Request’s outcome based on the status code of the response. 1xx is
|
|
Response’s HTTP status code if available (for example, |
|
Request’s URI template prior to variable substitution, if possible (for example,
|
To customize the tags, and depending on your choice of client, you can provide
a @Bean
that implements RestTemplateExchangeTagsProvider
or
WebClientExchangeTagsProvider
. There are convenience static functions in
RestTemplateExchangeTags
and WebClientExchangeTags
.
Cache Metrics
Auto-configuration enables the instrumentation of all available Cache
s on startup
with metrics prefixed with cache
. Cache instrumentation is standardized for a basic set
of metrics. Additional, cache-specific metrics are also available.
The following cache libraries are supported:
-
Caffeine
-
EhCache 2
-
Hazelcast
-
Any compliant JCache (JSR-107) implementation
Metrics are tagged by the name of the cache and by the name of the CacheManager
that is
derived from the bean name.
Only caches that are available on startup are bound to the registry. For caches
created on-the-fly or programmatically after the startup phase, an explicit registration
is required. A CacheMetricsRegistrar bean is made available to make that process easier.
|
DataSource Metrics
Auto-configuration enables the instrumentation of all available DataSource
objects with
metrics prefixed with jdbc.connections
. Data source instrumentation results in gauges
representing the currently active, idle, maximum allowed, and minimum allowed connections
in the pool.
Metrics are also tagged by the name of the DataSource
computed based on the bean name.
By default, Spring Boot provides metadata for all supported data sources; you can
add additional DataSourcePoolMetadataProvider beans if your favorite data source isn’t
supported out of the box. See DataSourcePoolMetadataProvidersConfiguration for examples.
|
Also, Hikari-specific metrics are exposed with a hikaricp
prefix. Each metric is tagged
by the name of the Pool (can be controlled with spring.datasource.name
).
Hibernate Metrics
Auto-configuration enables the instrumentation of all available Hibernate
EntityManagerFactory
instances that have statistics enabled with a metric named
hibernate
.
Metrics are also tagged by the name of the EntityManagerFactory
that is derived from
the bean name.
To enable statistics, the standard JPA property hibernate.generate_statistics
must be
set to true
. You can enable that on the auto-configured EntityManagerFactory
as shown
in the following example:
spring.jpa.properties.hibernate.generate_statistics=true
5.6.4. Registering custom metrics
To register custom metrics, inject MeterRegistry
into your component, as shown in the
following example:
class Dictionary {
private final List<String> words = new CopyOnWriteArrayList<>();
Dictionary(MeterRegistry registry) {
registry.gaugeCollectionSize("dictionary.size", Tags.empty(), this.words);
}
// …
}
If you find that you repeatedly instrument a suite of metrics across components or
applications, you may encapsulate this suite in a MeterBinder
implementation. By
default, metrics from all MeterBinder
beans will be automatically bound to
the Spring-managed MeterRegistry
.
5.6.5. Customizing individual metrics
If you need to apply customizations to specific Meter
instances you can use the
io.micrometer.core.instrument.config.MeterFilter
interface. By default, all
MeterFilter
beans will be automatically applied to the micrometer
MeterRegistry.Config
.
For example, if you want to rename the mytag.region
tag to mytag.area
for
all meter IDs beginning with com.example
, you can do the following:
@Bean
public MeterFilter renameRegionTagMeterFilter() {
return MeterFilter.renameTag("com.example", "mytag.region", "mytag.area");
}
Common tags
Common tags are generally used for dimensional drill-down on the operating environment like host, instance, region, stack, etc. Commons tags are applied to all meters and can be configured as shown in the following example:
management.metrics.tags.region=us-east-1
management.metrics.tags.stack=prod
The example above adds region
and stack
tags to all meters with a value of
us-east-1
and prod
respectively.
The order of common tags is important if you are using Graphite. As the order of
common tags cannot be guaranteed using this approach, Graphite users are advised to define
a custom MeterFilter instead.
|
Per-meter properties
In addition to MeterFilter
beans, it’s also possible to apply a limited set of
customization on a per-meter basis using properties. Per-meter customizations apply to
any all meter IDs that start with the given name. For example, the following will disable
any meters that have an ID starting with example.remote
management.metrics.enable.example.remote=false
The following properties allow per-meter customization:
Property | Description |
---|---|
|
Whether to deny meters from emitting any metrics. |
|
Whether to publish a histogram suitable for computing aggregable (across dimension) percentile approximations. |
|
Publish less histogram buckets by clamping the range of expected values. |
|
Publish percentile values computed in your application |
|
Publish a cumulative histogram with buckets defined by your SLAs. |
For more details on concepts behind percentiles-histogram
, percentiles
and sla
refer to the "Histograms
and percentiles" section of the micrometer documentation.
5.6.6. Metrics endpoint
Spring Boot provides a metrics
endpoint that can be used diagnostically to examine the
metrics collected by an application. The endpoint is not available by default and must be
exposed, see exposing endpoints for more
details.
Navigating to /actuator/metrics
displays a list of available meter names. You can drill
down to view information about a particular meter by providing its name as a selector,
e.g. /actuator/metrics/jvm.memory.max
.
The name you use here should match the name used in the code, not the name after it has
been naming-convention normalized for a monitoring system it is shipped to. In other
words, if |
You can also add any number of tag=KEY:VALUE
query parameters to the end of the URL to
dimensionally drill down on a meter, e.g.
/actuator/metrics/jvm.memory.max?tag=area:nonheap
.
The reported measurements are the sum of the statistics of all meters matching the meter
name and any tags that have been applied. So in the example above, the returned "Value"
statistic is the sum of the maximum memory footprints of "Code Cache",
"Compressed Class Space", and "Metaspace" areas of the heap. If you just wanted to see the
maximum size for the "Metaspace", you could add an additional |
5.7. Auditing
Once Spring Security is in play, Spring Boot Actuator has a flexible audit framework that publishes events (by default, “authentication success”, “failure” and “access denied” exceptions). This feature can be very useful for reporting and for implementing a lock-out policy based on authentication failures.
Auditing can be enabled by providing a bean of type AuditEventRepository
in your application’s
configuration. For convenience, Spring Boot offers an InMemoryAuditEventRepository
.
InMemoryAuditEventRepository
has limited capabilities and we recommend using it only for development
environments. For production environments, consider creating your own alternative AuditEventRepository
implementation.
5.7.1. Custom Auditing
To customize published security events, you can provide your own implementations of
AbstractAuthenticationAuditListener
and AbstractAuthorizationAuditListener
.
You can also use the audit services for your own business events. To do so, either inject
the AuditEventRepository
bean into your own components and use that directly or
publish an AuditApplicationEvent
with the Spring ApplicationEventPublisher
(by
implementing ApplicationEventPublisherAware
).
5.8. HTTP Tracing
HTTP Tracing can be enabled by providing a bean of type HttpTraceRepository
in your application’s
configuration. For convenience, Spring Boot offers an InMemoryHttpTraceRepository
that stores traces
for the last 100 request-response exchanges, by default. InMemoryHttpTraceRepository
is limited
compared to other tracing solutions and we recommend using it only for development environments.
For production environments, use of a production-ready tracing or observability solution, such as
Zipkin or Spring Cloud Sleuth, is recommended. Alternatively, create your own HttpTraceRepository
that meets your needs.
The httptrace
endpoint can be used to obtain information about the request-response exchanges that
are stored in the HttpTraceRepository
.
5.9. Process Monitoring
In the spring-boot
module, you can find two classes to create files that are often
useful for process monitoring:
-
ApplicationPidFileWriter
creates a file containing the application PID (by default, in the application directory with a file name ofapplication.pid
). -
WebServerPortFileWriter
creates a file (or files) containing the ports of the running web server (by default, in the application directory with a file name ofapplication.port
).
By default, these writers are not activated, but you can enable:
5.9.1. Extending Configuration
In the META-INF/spring.factories
file, you can activate the listener(s) that writes a
PID file, as shown in the following example:
org.springframework.context.ApplicationListener=\ org.springframework.boot.context.ApplicationPidFileWriter,\ org.springframework.boot.web.context.WebServerPortFileWriter
5.10. Cloud Foundry Support
Spring Boot’s actuator module includes additional support that is activated when you
deploy to a compatible Cloud Foundry instance. The /cloudfoundryapplication
path
provides an alternative secured route to all @Endpoint
beans.
The extended support lets Cloud Foundry management UIs (such as the web application that you can use to view deployed applications) be augmented with Spring Boot actuator information. For example, an application status page may include full health information instead of the typical “running” or “stopped” status.
The /cloudfoundryapplication path is not directly accessible to regular users.
In order to use the endpoint, a valid UAA token must be passed with the request.
|
5.10.1. Disabling Extended Cloud Foundry Actuator Support
If you want to fully disable the /cloudfoundryapplication
endpoints, you can add the
following setting to your application.properties
file:
management.cloudfoundry.enabled=false
5.10.2. Cloud Foundry Self-signed Certificates
By default, the security verification for /cloudfoundryapplication
endpoints makes SSL
calls to various Cloud Foundry services. If your Cloud Foundry UAA or Cloud Controller
services use self-signed certificates, you need to set the following property:
management.cloudfoundry.skip-ssl-validation=true
5.10.3. Custom context path
If the server’s context-path has been configured to anything other than /
, the Cloud
Foundry endpoints will not be available at the root of the application. For example, if
server.servlet.context-path=/app
, Cloud Foundry endpoints will be available at
/app/cloudfoundryapplication/*
.
If you expect the Cloud Foundry endpoints to always be available at
/cloudfoundryapplication/*
, regardless of the server’s context-path, you will need to
explicitly configure that in your application. The configuration will differ depending on
the web server in use. For Tomcat, the following configuration can be added:
@Bean
public TomcatServletWebServerFactory servletWebServerFactory() {
return new TomcatServletWebServerFactory() {
@Override
protected void prepareContext(Host host, ServletContextInitializer[] initializers) {
super.prepareContext(host, initializers);
StandardContext child = new StandardContext();
child.addLifecycleListener(new Tomcat.FixContextListener());
child.setPath("/cloudfoundryapplication");
ServletContainerInitializer initializer = getServletContextInitializer(getContextPath());
child.addServletContainerInitializer(initializer, Collections.emptySet());
child.setCrossContext(true);
host.addChild(child);
}
};
}
private ServletContainerInitializer getServletContextInitializer(String contextPath) {
return (c, context) -> {
Servlet servlet = new GenericServlet() {
@Override
public void service(ServletRequest req, ServletResponse res) throws ServletException, IOException {
ServletContext context = req.getServletContext().getContext(contextPath);
context.getRequestDispatcher("/cloudfoundryapplication").forward(req, res);
}
};
context.addServlet("cloudfoundry", servlet).addMapping("/*");
};
}
5.11. What to Read Next
If you want to explore some of the concepts discussed in this chapter, you can take a look at the actuator sample applications. You also might want to read about graphing tools such as Graphite.
Otherwise, you can continue on, to read about ‘deployment options’ or jump ahead for some in-depth information about Spring Boot’s build tool plugins.
6. Deploying Spring Boot Applications
Spring Boot’s flexible packaging options provide a great deal of choice when it comes to deploying your application. You can deploy Spring Boot applications to a variety of cloud platforms, to container images (such as Docker), or to virtual/real machines.
This section covers some of the more common deployment scenarios.
6.1. Deploying to the Cloud
Spring Boot’s executable jars are ready-made for most popular cloud PaaS (Platform-as-a-Service) providers. These providers tend to require that you “bring your own container”. They manage application processes (not Java applications specifically), so they need an intermediary layer that adapts your application to the cloud’s notion of a running process.
Two popular cloud providers, Heroku and Cloud Foundry, employ a “buildpack” approach.
The buildpack wraps your deployed code in whatever is needed to start your application.
It might be a JDK and a call to java
, an embedded web server, or a full-fledged
application server. A buildpack is pluggable, but ideally you should be able to get by
with as few customizations to it as possible. This reduces the footprint of functionality
that is not under your control. It minimizes divergence between development and production
environments.
Ideally, your application, like a Spring Boot executable jar, has everything that it needs to run packaged within it.
In this section, we look at what it takes to get the simple application that we developed in the “Getting Started” section up and running in the Cloud.
6.1.1. Cloud Foundry
Cloud Foundry provides default buildpacks that come into play if no other buildpack is
specified. The Cloud Foundry Java
buildpack has excellent support for Spring applications, including Spring Boot. You can
deploy stand-alone executable jar applications as well as traditional .war
packaged
applications.
Once you have built your application (by using, for example, mvn clean package
) and have
installed the cf
command line tool, deploy your application by using the cf push
command, substituting
the path to your compiled .jar
. Be sure to have
logged in with
your cf
command line client before pushing an application. The following line shows
using the cf push
command to deploy an application:
$ cf push acloudyspringtime -p target/demo-0.0.1-SNAPSHOT.jar
In the preceding example, we substitute acloudyspringtime for whatever value you
give cf as the name of your application.
|
See the cf push
documentation for more options. If there is a Cloud Foundry
manifest.yml
file present in the same directory, it is considered.
At this point, cf
starts uploading your application, producing output similar to the
following example:
Uploading acloudyspringtime... OK Preparing to start acloudyspringtime... OK -----> Downloaded app package (8.9M) -----> Java Buildpack Version: v3.12 (offline) | https://github.com/cloudfoundry/java-buildpack.git#6f25b7e -----> Downloading Open Jdk JRE 1.8.0_121 from https://java-buildpack.cloudfoundry.org/openjdk/trusty/x86_64/openjdk-1.8.0_121.tar.gz (found in cache) Expanding Open Jdk JRE to .java-buildpack/open_jdk_jre (1.6s) -----> Downloading Open JDK Like Memory Calculator 2.0.2_RELEASE from https://java-buildpack.cloudfoundry.org/memory-calculator/trusty/x86_64/memory-calculator-2.0.2_RELEASE.tar.gz (found in cache) Memory Settings: -Xss349K -Xmx681574K -XX:MaxMetaspaceSize=104857K -Xms681574K -XX:MetaspaceSize=104857K -----> Downloading Container Certificate Trust Store 1.0.0_RELEASE from https://java-buildpack.cloudfoundry.org/container-certificate-trust-store/container-certificate-trust-store-1.0.0_RELEASE.jar (found in cache) Adding certificates to .java-buildpack/container_certificate_trust_store/truststore.jks (0.6s) -----> Downloading Spring Auto Reconfiguration 1.10.0_RELEASE from https://java-buildpack.cloudfoundry.org/auto-reconfiguration/auto-reconfiguration-1.10.0_RELEASE.jar (found in cache) Checking status of app 'acloudyspringtime'... 0 of 1 instances running (1 starting) ... 0 of 1 instances running (1 starting) ... 0 of 1 instances running (1 starting) ... 1 of 1 instances running (1 running) App started
Congratulations! The application is now live!
Once your application is live, you can verify the status of the deployed application by
using the cf apps
command, as shown in the following example:
$ cf apps Getting applications in ... OK name requested state instances memory disk urls ... acloudyspringtime started 1/1 512M 1G acloudyspringtime.cfapps.io ...
Once Cloud Foundry acknowledges that your application has been deployed, you should be
able to find the application at the URI given. In the preceding example, you could find
it at https://acloudyspringtime.cfapps.io/
.
Binding to Services
By default, metadata about the running application as well as service connection
information is exposed to the application as environment variables (for example:
$VCAP_SERVICES
). This architecture decision is due to Cloud Foundry’s polyglot (any
language and platform can be supported as a buildpack) nature. Process-scoped environment
variables are language agnostic.
Environment variables do not always make for the easiest API, so Spring Boot automatically
extracts them and flattens the data into properties that can be accessed through Spring’s
Environment
abstraction, as shown in the following example:
@Component
class MyBean implements EnvironmentAware {
private String instanceId;
@Override
public void setEnvironment(Environment environment) {
this.instanceId = environment.getProperty("vcap.application.instance_id");
}
// ...
}
All Cloud Foundry properties are prefixed with vcap
. You can use vcap
properties to
access application information (such as the public URL of the application) and service
information (such as database credentials). See the
‘CloudFoundryVcapEnvironmentPostProcessor’
Javadoc for complete details.
The Spring Cloud Connectors project
is a better fit for tasks such as configuring a DataSource. Spring Boot includes
auto-configuration support and a spring-boot-starter-cloud-connectors starter.
|
6.1.2. Heroku
Heroku is another popular PaaS platform. To customize Heroku builds, you provide a
Procfile
, which provides the incantation required to deploy an application. Heroku
assigns a port
for the Java application to use and then ensures that routing to the
external URI works.
You must configure your application to listen on the correct port. The following example
shows the Procfile
for our starter REST application:
web: java -Dserver.port=$PORT -jar target/demo-0.0.1-SNAPSHOT.jar
Spring Boot makes -D
arguments available as properties accessible from a Spring
Environment
instance. The server.port
configuration property is fed to the embedded
Tomcat, Jetty, or Undertow instance, which then uses the port when it starts up. The $PORT
environment variable is assigned to us by the Heroku PaaS.
This should be everything you need. The most common deployment workflow for Heroku
deployments is to git push
the code to production, as shown in the following example:
$ git push heroku master Initializing repository, done. Counting objects: 95, done. Delta compression using up to 8 threads. Compressing objects: 100% (78/78), done. Writing objects: 100% (95/95), 8.66 MiB | 606.00 KiB/s, done. Total 95 (delta 31), reused 0 (delta 0) -----> Java app detected -----> Installing OpenJDK 1.8... done -----> Installing Maven 3.3.1... done -----> Installing settings.xml... done -----> Executing: mvn -B -DskipTests=true clean install [INFO] Scanning for projects... Downloading: https://repo.spring.io/... Downloaded: https://repo.spring.io/... (818 B at 1.8 KB/sec) .... Downloaded: https://s3pository.heroku.com/jvm/... (152 KB at 595.3 KB/sec) [INFO] Installing /tmp/build_0c35a5d2-a067-4abc-a232-14b1fb7a8229/target/... [INFO] Installing /tmp/build_0c35a5d2-a067-4abc-a232-14b1fb7a8229/pom.xml ... [INFO] ------------------------------------------------------------------------ [INFO] BUILD SUCCESS [INFO] ------------------------------------------------------------------------ [INFO] Total time: 59.358s [INFO] Finished at: Fri Mar 07 07:28:25 UTC 2014 [INFO] Final Memory: 20M/493M [INFO] ------------------------------------------------------------------------ -----> Discovering process types Procfile declares types -> web -----> Compressing... done, 70.4MB -----> Launching... done, v6 https://agile-sierra-1405.herokuapp.com/ deployed to Heroku To [email protected]:agile-sierra-1405.git * [new branch] master -> master
Your application should now be up and running on Heroku. For more details, refer to Deploying Spring Boot Applications to Heroku.
6.1.3. OpenShift
OpenShift is the Red Hat public (and enterprise) extension of the Kubernetes container orchestration platform. Similarly to Kubernetes, OpenShift has many options for installing Spring Boot based applications.
OpenShift has many resources describing how to deploy Spring Boot applications, including:
6.1.4. Amazon Web Services (AWS)
Amazon Web Services offers multiple ways to install Spring Boot-based applications, either as traditional web applications (war) or as executable jar files with an embedded web server. The options include:
-
AWS Elastic Beanstalk
-
AWS Code Deploy
-
AWS OPS Works
-
AWS Cloud Formation
-
AWS Container Registry
Each has different features and pricing models. In this document, we describe only the simplest option: AWS Elastic Beanstalk.
AWS Elastic Beanstalk
As described in the official Elastic Beanstalk Java guide, there are two main options to deploy a Java application. You can either use the “Tomcat Platform” or the “Java SE platform”.
Using the Tomcat Platform
This option applies to Spring Boot projects that produce a war file. No special configuration is required. You need only follow the official guide.
Using the Java SE Platform
This option applies to Spring Boot projects that produce a jar file and run an embedded
web container. Elastic Beanstalk environments run an nginx instance on port 80 to proxy
the actual application, running on port 5000. To configure it, add the following line to
your application.properties
file:
server.port=5000
Upload binaries instead of sources
By default, Elastic Beanstalk uploads sources and compiles them in AWS. However, it is
best to upload the binaries instead. To do so, add lines similar to the following to your
|
Reduce costs by setting the environment type
By default an Elastic Beanstalk environment is load balanced. The load balancer has a significant cost. To avoid that cost, set the environment type to “Single instance”, as described in the Amazon documentation. You can also create single instance environments by using the CLI and the following command: eb create -s |
Summary
This is one of the easiest ways to get to AWS, but there are more things to cover, such as how to integrate Elastic Beanstalk into any CI / CD tool, use the Elastic Beanstalk Maven plugin instead of the CLI, and others. There is a blog post covering these topics more in detail.
6.1.5. Boxfuse and Amazon Web Services
Boxfuse works by turning your Spring Boot executable jar or war into a minimal VM image that can be deployed unchanged either on VirtualBox or on AWS. Boxfuse comes with deep integration for Spring Boot and uses the information from your Spring Boot configuration file to automatically configure ports and health check URLs. Boxfuse leverages this information both for the images it produces as well as for all the resources it provisions (instances, security groups, elastic load balancers, and so on).
Once you have created a Boxfuse account, connected it to
your AWS account, installed the latest version of the Boxfuse Client, and ensured that
the application has been built by Maven or Gradle (by using, for example, mvn clean
package
), you can deploy your Spring Boot application to AWS with a command similar to
the following:
$ boxfuse run myapp-1.0.jar -env=prod
See the boxfuse run
documentation for
more options. If there is a boxfuse.conf
file present in the current directory, it is considered.
By default, Boxfuse activates a Spring profile named boxfuse on startup. If your
executable jar or war contains an
application-boxfuse.properties file, Boxfuse bases its configuration on the
properties it contains.
|
At this point, boxfuse
creates an image for your application, uploads it, and configures
and starts the necessary resources on AWS, resulting in output similar to the following
example:
Fusing Image for myapp-1.0.jar ... Image fused in 00:06.838s (53937 K) -> axelfontaine/myapp:1.0 Creating axelfontaine/myapp ... Pushing axelfontaine/myapp:1.0 ... Verifying axelfontaine/myapp:1.0 ... Creating Elastic IP ... Mapping myapp-axelfontaine.boxfuse.io to 52.28.233.167 ... Waiting for AWS to create an AMI for axelfontaine/myapp:1.0 in eu-central-1 (this may take up to 50 seconds) ... AMI created in 00:23.557s -> ami-d23f38cf Creating security group boxfuse-sg_axelfontaine/myapp:1.0 ... Launching t2.micro instance of axelfontaine/myapp:1.0 (ami-d23f38cf) in eu-central-1 ... Instance launched in 00:30.306s -> i-92ef9f53 Waiting for AWS to boot Instance i-92ef9f53 and Payload to start at https://52.28.235.61/ ... Payload started in 00:29.266s -> https://52.28.235.61/ Remapping Elastic IP 52.28.233.167 to i-92ef9f53 ... Waiting 15s for AWS to complete Elastic IP Zero Downtime transition ... Deployment completed successfully. axelfontaine/myapp:1.0 is up and running at https://myapp-axelfontaine.boxfuse.io/
Your application should now be up and running on AWS.
See the blog post on deploying Spring Boot apps on EC2 as well as the documentation for the Boxfuse Spring Boot integration to get started with a Maven build to run the app.
6.1.6. Google Cloud
Google Cloud has several options that can be used to launch Spring Boot applications. The easiest to get started with is probably App Engine, but you could also find ways to run Spring Boot in a container with Container Engine or on a virtual machine with Compute Engine.
To run in App Engine, you can create a project in the UI first, which sets up a unique identifier for you and also sets up HTTP routes. Add a Java app to the project and leave it empty and then use the Google Cloud SDK to push your Spring Boot app into that slot from the command line or CI build.
App Engine Standard requires you to use WAR packaging. Follow these steps to deploy App Engine Standard application to Google Cloud.
Alternatively, App Engine Flex requires you to create an app.yaml
file to describe
the resources your app requires. Normally, you put this file in src/main/appengine
,
and it should resemble the following file:
service: default
runtime: java
env: flex
runtime_config:
jdk: openjdk8
handlers:
- url: /.*
script: this field is required, but ignored
manual_scaling:
instances: 1
health_check:
enable_health_check: False
env_variables:
ENCRYPT_KEY: your_encryption_key_here
You can deploy the app (for example, with a Maven plugin) by adding the project ID to the build configuration, as shown in the following example:
<plugin>
<groupId>com.google.cloud.tools</groupId>
<artifactId>appengine-maven-plugin</artifactId>
<version>1.3.0</version>
<configuration>
<project>myproject</project>
</configuration>
</plugin>
Then deploy with mvn appengine:deploy
(if you need to authenticate first, the build
fails).
6.2. Installing Spring Boot Applications
In addition to running Spring Boot applications by using java -jar
, it is also
possible to make fully executable applications for Unix systems. A fully executable jar
can be executed like any other executable binary or it can be
registered with init.d
or systemd
. This makes it very easy to
install and manage Spring Boot applications in common production environments.
Fully executable jars work by embedding an extra script at the front of the file.
Currently, some tools do not accept this format, so you may not always be able to use this
technique. For example, jar -xf may silently fail to extract a jar or war that has been
made fully executable. It is recommended that you make your jar or war fully executable
only if you intend to execute it directly, rather than running it with java -jar
or deploying it to a servlet container.
|
To create a ‘fully executable’ jar with Maven, use the following plugin configuration:
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
<configuration>
<executable>true</executable>
</configuration>
</plugin>
The following example shows the equivalent Gradle configuration:
bootJar {
launchScript()
}
You can then run your application by typing ./my-application.jar
(where my-application
is the name of your artifact). The directory containing the jar is used as your
application’s working directory.
6.2.1. Supported Operating Systems
The default script supports most Linux distributions and is tested on CentOS and Ubuntu.
Other platforms, such as OS X and FreeBSD, require the use of a custom
embeddedLaunchScript
.
6.2.2. Unix/Linux Services
Spring Boot application can be easily started as Unix/Linux services by using either
init.d
or systemd
.
Installation as an init.d
Service (System V)
If you configured Spring Boot’s Maven or Gradle plugin to generate a fully executable jar, and you do not use a custom embeddedLaunchScript
, your
application can be used as an init.d
service. To do so, symlink the jar to init.d
to
support the standard start
, stop
, restart
, and status
commands.
The script supports the following features:
-
Starts the services as the user that owns the jar file
-
Tracks the application’s PID by using
/var/run/<appname>/<appname>.pid
-
Writes console logs to
/var/log/<appname>.log
Assuming that you have a Spring Boot application installed in /var/myapp
, to install a
Spring Boot application as an init.d
service, create a symlink, as follows:
$ sudo ln -s /var/myapp/myapp.jar /etc/init.d/myapp
Once installed, you can start and stop the service in the usual way. For example, on a Debian-based system, you could start it with the following command:
$ service myapp start
If your application fails to start, check the log file written to
/var/log/<appname>.log for errors.
|
You can also flag the application to start automatically by using your standard operating system tools. For example, on Debian, you could use the following command:
$ update-rc.d myapp defaults <priority>
Securing an init.d
Service
The following is a set of guidelines on how to secure a Spring Boot application that runs as an init.d service. It is not intended to be an exhaustive list of everything that should be done to harden an application and the environment in which it runs. |
When executed as root, as is the case when root is being used to start an init.d service,
the default executable script runs the application as the user who owns the jar file. You
should never run a Spring Boot application as root
, so your application’s jar file
should never be owned by root. Instead, create a specific user to run your application and
use chown
to make it the owner of the jar file, as shown in the following example:
$ chown bootapp:bootapp your-app.jar
In this case, the default executable script runs the application as the bootapp
user.
To reduce the chances of the application’s user account being compromised, you should
consider preventing it from using a login shell. For example, you can set the account’s
shell to /usr/sbin/nologin .
|
You should also take steps to prevent the modification of your application’s jar file. Firstly, configure its permissions so that it cannot be written and can only be read or executed by its owner, as shown in the following example:
$ chmod 500 your-app.jar
Second, you should also take steps to limit the damage if your application or the account
that’s running it is compromised. If an attacker does gain access, they could make the jar
file writable and change its contents. One way to protect against this is to make it
immutable by using chattr
, as shown in the following example:
$ sudo chattr +i your-app.jar
This will prevent any user, including root, from modifying the jar.
If root is used to control the application’s service and you
use a .conf
file to customize its
startup, the .conf
file is read and evaluated by the root user. It should be secured
accordingly. Use chmod
so that the file can only be read by the owner and use chown
to
make root the owner, as shown in the following example:
$ chmod 400 your-app.conf $ sudo chown root:root your-app.conf
Installation as a systemd
Service
systemd
is the successor of the System V init system and is now being used by many
modern Linux distributions. Although you can continue to use init.d
scripts with
systemd
, it is also possible to launch Spring Boot applications by using systemd
‘service’ scripts.
Assuming that you have a Spring Boot application installed in /var/myapp
, to install a
Spring Boot application as a systemd
service, create a script named myapp.service
and
place it in /etc/systemd/system
directory. The following script offers an example:
[Unit] Description=myapp After=syslog.target [Service] User=myapp ExecStart=/var/myapp/myapp.jar SuccessExitStatus=143 [Install] WantedBy=multi-user.target
Remember to change the Description , User , and ExecStart fields for your
application.
|
The ExecStart field does not declare the script action command, which means that
the run command is used by default.
|
Note that, unlike when running as an init.d
service, the user that runs the application,
the PID file, and the console log file are managed by systemd
itself and therefore must
be configured by using appropriate fields in the ‘service’ script. Consult the
service unit
configuration man page for more details.
To flag the application to start automatically on system boot, use the following command:
$ systemctl enable myapp.service
Refer to man systemctl
for more details.
Customizing the Startup Script
The default embedded startup script written by the Maven or Gradle plugin can be
customized in a number of ways. For most people, using the default script along with a few
customizations is usually enough. If you find you cannot customize something that you need
to, use the embeddedLaunchScript
option to write your own file entirely.
Customizing the Start Script when It Is Written
It often makes sense to customize elements of the start script as it is written into the jar file. For example, init.d scripts can provide a “description”. Since you know the description up front (and it need not change), you may as well provide it when the jar is generated.
To customize written elements, use the embeddedLaunchScriptProperties
option of the
Spring Boot Maven plugin or the
properties
property of the Spring Boot Gradle plugin’s launchScript
.
The following property substitutions are supported with the default script:
Name | Description | Gradle default | Maven default |
---|---|---|---|
|
The script mode. |
|
|
|
The |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
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|
|
Single-line version of |
|
|
|
|
|
|
|
|
|
|
The default value for |
Folder containing the jar |
Folder containing the jar |
|
Reference to a file script that should be inlined in the default launch script.
This can be used to set environmental variables such as |
||
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Default value for |
||
|
Default value for |
||
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Default value for |
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|
Default value for the name of the PID file in |
||
|
Whether the |
|
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|
Default value for |
60 |
60 |
Customizing a Script When It Runs
For items of the script that need to be customized after the jar has been written, you can use environment variables or a config file.
The following environment properties are supported with the default script:
Variable | Description |
---|---|
|
The “mode” of operation. The default depends on the way the jar was built but is
usually |
|
Whether the |
|
The root name of the pid folder ( |
|
The name of the folder in which to put log files ( |
|
The name of the folder from which to read .conf files (same folder as jar-file by default). |
|
The name of the log file in the |
|
The name of the app. If the jar is run from a symlink, the script guesses the app name. If it is not a symlink or you want to explicitly set the app name, this can be useful. |
|
The arguments to pass to the program (the Spring Boot app). |
|
The location of the |
|
Options that are passed to the JVM when it is launched. |
|
The explicit location of the jar file, in case the script is being used to launch a jar that it is not actually embedded. |
|
If not empty, sets the |
|
The time in seconds to wait when stopping the application before forcing a shutdown ( |
The PID_FOLDER , LOG_FOLDER , and LOG_FILENAME variables are only valid for an
init.d service. For systemd , the equivalent customizations are made by using the
‘service’ script. See the
service unit
configuration man page for more details.
|
With the exception of JARFILE
and APP_NAME
, the settings listed in the preceding
section can be configured by using a .conf
file. The file is expected to be next to the
jar file and have the same name but suffixed with .conf
rather than .jar
. For example,
a jar named /var/myapp/myapp.jar
uses the configuration file named
/var/myapp/myapp.conf
, as shown in the following example:
JAVA_OPTS=-Xmx1024M LOG_FOLDER=/custom/log/folder
If you do not like having the config file next to the jar file, you can set a
CONF_FOLDER environment variable to customize the location of the config file.
|
To learn about securing this file appropriately, see the guidelines for securing an init.d service.
6.2.3. Microsoft Windows Services
A Spring Boot application can be started as a Windows service by using
winsw
.
A (separately maintained sample) describes step-by-step how you can create a Windows service for your Spring Boot application.
6.3. What to Read Next
Check out the Cloud Foundry, Heroku, OpenShift, and Boxfuse web sites for more information about the kinds of features that a PaaS can offer. These are just four of the most popular Java PaaS providers. Since Spring Boot is so amenable to cloud-based deployment, you can freely consider other providers as well.
The next section goes on to cover the Spring Boot CLI, or you can jump ahead to read about build tool plugins.
7. Spring Boot CLI
The Spring Boot CLI is a command line tool that you can use if you want to quickly develop a Spring application. It lets you run Groovy scripts, which means that you have a familiar Java-like syntax without so much boilerplate code. You can also bootstrap a new project or write your own command for it.
7.1. Installing the CLI
The Spring Boot CLI (Command-Line Interface) can be installed manually by using SDKMAN! (the SDK Manager) or by using Homebrew or MacPorts if you are an OSX user. See Installing the Spring Boot CLI in the “Getting started” section for comprehensive installation instructions.
7.2. Using the CLI
Once you have installed the CLI, you can run it by typing spring
and pressing Enter at
the command line. If you run spring
without any arguments, a simple help screen is
displayed, as follows:
$ spring usage: spring [--help] [--version] <command> [<args>] Available commands are: run [options] <files> [--] [args] Run a spring groovy script ... more command help is shown here
You can type spring help
to get more details about any of the supported commands, as
shown in the following example:
$ spring help run spring run - Run a spring groovy script usage: spring run [options] <files> [--] [args] Option Description ------ ----------- --autoconfigure [Boolean] Add autoconfigure compiler transformations (default: true) --classpath, -cp Additional classpath entries -e, --edit Open the file with the default system editor --no-guess-dependencies Do not attempt to guess dependencies --no-guess-imports Do not attempt to guess imports -q, --quiet Quiet logging -v, --verbose Verbose logging of dependency resolution --watch Watch the specified file for changes
The version
command provides a quick way to check which version of Spring Boot you are
using, as follows:
$ spring version Spring CLI v2.2.0.M5
7.2.1. Running Applications with the CLI
You can compile and run Groovy source code by using the run
command. The Spring Boot CLI
is completely self-contained, so you do not need any external Groovy installation.
The following example shows a “hello world” web application written in Groovy:
@RestController
class WebApplication {
@RequestMapping("/")
String home() {
"Hello World!"
}
}
To compile and run the application, type the following command:
$ spring run hello.groovy
To pass command-line arguments to the application, use --
to separate the commands
from the “spring” command arguments, as shown in the following example:
$ spring run hello.groovy -- --server.port=9000
To set JVM command line arguments, you can use the JAVA_OPTS
environment variable, as
shown in the following example:
$ JAVA_OPTS=-Xmx1024m spring run hello.groovy
When setting JAVA_OPTS on Microsoft Windows, make sure to quote the entire
instruction, such as set "JAVA_OPTS=-Xms256m -Xmx2048m" . Doing so ensures the values
are properly passed to the process.
|
Deduced “grab” Dependencies
Standard Groovy includes a @Grab
annotation, which lets you declare dependencies on
third-party libraries. This useful technique lets Groovy download jars in the same way as
Maven or Gradle would but without requiring you to use a build tool.
Spring Boot extends this technique further and tries to deduce which libraries to “grab”
based on your code. For example, since the WebApplication
code shown previously uses
@RestController
annotations, Spring Boot grabs "Tomcat" and "Spring MVC".
The following items are used as “grab hints”:
Items | Grabs |
---|---|
|
JDBC Application. |
|
JMS Application. |
|
Caching abstraction. |
|
JUnit. |
|
RabbitMQ. |
extends |
Spock test. |
|
Spring Batch. |
|
Spring Integration. |
|
Spring MVC + Embedded Tomcat. |
|
Spring Security. |
|
Spring Transaction Management. |
See subclasses of
CompilerAutoConfiguration
in the Spring Boot CLI source code to understand exactly how customizations are applied.
|
Deduced “grab” Coordinates
Spring Boot extends Groovy’s standard @Grab
support by letting you specify a dependency
without a group or version (for example, @Grab('freemarker')
). Doing so consults Spring
Boot’s default dependency metadata to deduce the artifact’s group and version.
The default metadata is tied to the version of the CLI that you use. it changes only when you move to a new version of the CLI, putting you in control of when the versions of your dependencies may change. A table showing the dependencies and their versions that are included in the default metadata can be found in the appendix. |
Default Import Statements
To help reduce the size of your Groovy code, several import
statements are automatically
included. Notice how the preceding example refers to @Component
, @RestController
, and
@RequestMapping
without needing to use fully-qualified names or import
statements.
Many Spring annotations work without using import statements. Try running your
application to see what fails before adding imports.
|
Automatic Main Method
Unlike the equivalent Java application, you do not need to include a
public static void main(String[] args)
method with your Groovy
scripts. A
SpringApplication
is automatically created, with your compiled code acting as the
source
.
Custom Dependency Management
By default, the CLI uses the dependency management declared in spring-boot-dependencies
when resolving @Grab
dependencies. Additional dependency management, which overrides
the default dependency management, can be configured by using the
@DependencyManagementBom
annotation. The annotation’s value should specify the
coordinates (groupId:artifactId:version
) of one or more Maven BOMs.
For example, consider the following declaration:
@DependencyManagementBom("com.example.custom-bom:1.0.0")
The preceding declaration picks up custom-bom-1.0.0.pom
in a Maven repository under
com/example/custom-versions/1.0.0/
.
When you specify multiple BOMs, they are applied in the order in which you declare them, as shown in the following example:
@DependencyManagementBom(["com.example.custom-bom:1.0.0",
"com.example.another-bom:1.0.0"])
The preceding example indicates that the dependency management in another-bom
overrides
the dependency management in custom-bom
.
You can use @DependencyManagementBom
anywhere that you can use @Grab
. However, to
ensure consistent ordering of the dependency management, you can use
@DependencyManagementBom
at most once in your application. A useful source of dependency
management (which is a superset of Spring Boot’s dependency management) is the
Spring IO Platform, which you might include with the following
line:
@DependencyManagementBom('io.spring.platform:platform-bom:1.1.2.RELEASE')
7.2.2. Applications with Multiple Source Files
You can use “shell globbing” with all commands that accept file input. Doing so lets you use multiple files from a single directory, as shown in the following example:
$ spring run *.groovy
7.2.3. Packaging Your Application
You can use the jar
command to package your application into a self-contained executable
jar file, as shown in the following example:
$ spring jar my-app.jar *.groovy
The resulting jar contains the classes produced by compiling the application and all of
the application’s dependencies so that it can then be run by using java -jar
. The jar
file also contains entries from the application’s classpath. You can add and remove
explicit paths to the jar by using --include
and --exclude
. Both are comma-separated,
and both accept prefixes, in the form of “+” and “-”, to signify that they should be
removed from the defaults. The default includes are as follows:
public/**, resources/**, static/**, templates/**, META-INF/**, *
The default excludes are as follows:
.*, repository/**, build/**, target/**, **/*.jar, **/*.groovy
Type spring help jar
on the command line for more information.
7.2.4. Initialize a New Project
The init
command lets you create a new project by using start.spring.io without
leaving the shell, as shown in the following example:
$ spring init --dependencies=web,data-jpa my-project Using service at https://start.spring.io Project extracted to '/Users/developer/example/my-project'
The preceding example creates a my-project
directory with a Maven-based project that
uses spring-boot-starter-web
and spring-boot-starter-data-jpa
. You can list the
capabilities of the service by using the --list
flag, as shown in the following example:
$ spring init --list ======================================= Capabilities of https://start.spring.io ======================================= Available dependencies: ----------------------- actuator - Actuator: Production ready features to help you monitor and manage your application ... web - Web: Support for full-stack web development, including Tomcat and spring-webmvc websocket - Websocket: Support for WebSocket development ws - WS: Support for Spring Web Services Available project types: ------------------------ gradle-build - Gradle Config [format:build, build:gradle] gradle-project - Gradle Project [format:project, build:gradle] maven-build - Maven POM [format:build, build:maven] maven-project - Maven Project [format:project, build:maven] (default) ...
The init
command supports many options. See the help
output for more details. For
instance, the following command creates a Gradle project that uses Java 8 and war
packaging:
$ spring init --build=gradle --java-version=1.8 --dependencies=websocket --packaging=war sample-app.zip Using service at https://start.spring.io Content saved to 'sample-app.zip'
7.2.5. Using the Embedded Shell
Spring Boot includes command-line completion scripts for the BASH and zsh shells. If you
do not use either of these shells (perhaps you are a Windows user), you can use the
shell
command to launch an integrated shell, as shown in the following example:
$ spring shell Spring Boot (v2.2.0.M5) Hit TAB to complete. Type \'help' and hit RETURN for help, and \'exit' to quit.
From inside the embedded shell, you can run other commands directly:
$ version Spring CLI v2.2.0.M5
The embedded shell supports ANSI color output as well as tab
completion. If you need to
run a native command, you can use the !
prefix. To exit the embedded shell, press
ctrl-c
.
7.2.6. Adding Extensions to the CLI
You can add extensions to the CLI by using the install
command. The command takes one
or more sets of artifact coordinates in the format group:artifact:version
, as shown in
the following example:
$ spring install com.example:spring-boot-cli-extension:1.0.0.RELEASE
In addition to installing the artifacts identified by the coordinates you supply, all of the artifacts' dependencies are also installed.
To uninstall a dependency, use the uninstall
command. As with the install
command, it
takes one or more sets of artifact coordinates in the format of group:artifact:version
,
as shown in the following example:
$ spring uninstall com.example:spring-boot-cli-extension:1.0.0.RELEASE
It uninstalls the artifacts identified by the coordinates you supply and their dependencies.
To uninstall all additional dependencies, you can use the --all
option, as shown in the
following example:
$ spring uninstall --all
7.3. Developing Applications with the Groovy Beans DSL
Spring Framework 4.0 has native support for a beans{}
“DSL” (borrowed from
Grails), and you can embed bean definitions in your Groovy application
scripts by using the same format. This is sometimes a good way to include external
features like middleware declarations, as shown in the following example:
@Configuration(proxyBeanMethods = false)
class Application implements CommandLineRunner {
@Autowired
SharedService service
@Override
void run(String... args) {
println service.message
}
}
import my.company.SharedService
beans {
service(SharedService) {
message = "Hello World"
}
}
You can mix class declarations with beans{}
in the same file as long as they stay at
the top level, or, if you prefer, you can put the beans DSL in a separate file.
7.4. Configuring the CLI with settings.xml
The Spring Boot CLI uses Aether, Maven’s dependency resolution engine, to resolve
dependencies. The CLI makes use of the Maven configuration found in ~/.m2/settings.xml
to configure Aether. The following configuration settings are honored by the CLI:
-
Offline
-
Mirrors
-
Servers
-
Proxies
-
Profiles
-
Activation
-
Repositories
-
-
Active profiles
See Maven’s settings documentation for further information.
7.5. What to Read Next
There are some sample groovy scripts available from the GitHub repository that you can use to try out the Spring Boot CLI. There is also extensive Javadoc throughout the source code.
If you find that you reach the limit of the CLI tool, you probably want to look at converting your application to a full Gradle or Maven built “Groovy project”. The next section covers Spring Boot’s "Build tool plugins", which you can use with Gradle or Maven.
8. Build Tool Plugins
Spring Boot provides build tool plugins for Maven and Gradle. The plugins offer a variety of features, including the packaging of executable jars. This section provides more details on both plugins as well as some help should you need to extend an unsupported build system. If you are just getting started, you might want to read “Build Systems” from the “Using Spring Boot” section first.
8.1. Spring Boot Maven Plugin
The Spring Boot Maven Plugin provides Spring Boot support in Maven, letting you package executable jar or war archives and run an application “in-place”. To use it, you must use Maven 3.2 (or later).
See the Spring Boot Maven Plugin Site for complete plugin documentation. |
8.1.1. Including the Plugin
To use the Spring Boot Maven Plugin, include the appropriate XML in the plugins
section of your pom.xml
, as shown in the following example:
<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<!-- ... -->
<build>
<plugins>
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
<version>2.2.0.M5</version>
<executions>
<execution>
<goals>
<goal>repackage</goal>
</goals>
</execution>
</executions>
</plugin>
</plugins>
</build>
</project>
The preceding configuration repackages a jar or war that is built during the package
phase of the Maven lifecycle. The following example shows both the repackaged jar as well
as the original jar in the target
directory:
$ mvn package $ ls target/*.jar target/myproject-1.0.0.jar target/myproject-1.0.0.jar.original
If you do not include the <execution/>
configuration, as shown in the prior example, you
can run the plugin on its own (but only if the package goal is used as well), as shown in
the following example:
$ mvn package spring-boot:repackage $ ls target/*.jar target/myproject-1.0.0.jar target/myproject-1.0.0.jar.original
If you use a milestone or snapshot release, you also need to add the appropriate
pluginRepository
elements, as shown in the following listing:
<pluginRepositories>
<pluginRepository>
<id>spring-snapshots</id>
<url>https://repo.spring.io/snapshot</url>
</pluginRepository>
<pluginRepository>
<id>spring-milestones</id>
<url>https://repo.spring.io/milestone</url>
</pluginRepository>
</pluginRepositories>
8.1.2. Packaging Executable Jar and War Files
Once spring-boot-maven-plugin
has been included in your pom.xml
, it automatically
tries to rewrite archives to make them executable by using the spring-boot:repackage
goal. You should configure your project to build a jar or war (as appropriate) by using
the usual packaging
element, as shown in the following example:
<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
<!-- ... -->
<packaging>jar</packaging>
<!-- ... -->
</project>
Your existing archive is enhanced by Spring Boot during the package
phase. The main
class that you want to launch can be specified either by using a configuration option, as
shown below, or by adding a Main-Class
attribute to the manifest. If you do not specify
a main class, the plugin searches for a class with a public static void main(String[] args)
method.
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
<configuration>
<mainClass>com.example.app.Main</mainClass>
</configuration>
</plugin>
To build and run a project artifact, you can type the following:
$ mvn package $ java -jar target/mymodule-0.0.1-SNAPSHOT.jar
To build a war file that is both executable and deployable into an external container, you need to mark the embedded container dependencies as “provided”, as shown in the following example:
<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
<!-- ... -->
<packaging>war</packaging>
<!-- ... -->
<dependencies>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-tomcat</artifactId>
<scope>provided</scope>
</dependency>
<!-- ... -->
</dependencies>
</project>
See the “Create a Deployable War File” section for more details on how to create a deployable war file. |
Advanced configuration options and examples are available in the plugin info page.
8.2. Spring Boot Gradle Plugin
The Spring Boot Gradle Plugin provides Spring Boot support in Gradle, letting you package
executable jar or war archives, run Spring Boot applications, and use the dependency
management provided by spring-boot-dependencies
. It requires Gradle 5.x (4.10 is also
supported but this support is deprecated and will be removed in a future release). Please
refer to the plugin’s documentation to learn more:
8.3. Spring Boot AntLib Module
The Spring Boot AntLib module provides basic Spring Boot support for Apache Ant. You can
use the module to create executable jars. To use the module, you need to declare an
additional spring-boot
namespace in your build.xml
, as shown in the following example:
<project xmlns:ivy="antlib:org.apache.ivy.ant"
xmlns:spring-boot="antlib:org.springframework.boot.ant"
name="myapp" default="build">
...
</project>
You need to remember to start Ant using the -lib
option, as shown in the following
example:
$ ant -lib <folder containing spring-boot-antlib-2.2.0.M5.jar>
The “Using Spring Boot” section includes a more complete example of
using Apache Ant with spring-boot-antlib .
|
8.3.1. Spring Boot Ant Tasks
Once the spring-boot-antlib
namespace has been declared, the following additional tasks
are available:
spring-boot:exejar
You can use the exejar
task to create a Spring Boot executable jar. The following
attributes are supported by the task:
Attribute | Description | Required |
---|---|---|
|
The destination jar file to create |
Yes |
|
The root directory of Java class files |
Yes |
|
The main application class to run |
No (the default is the first class found that declares a |
The following nested elements can be used with the task:
Element | Description |
---|---|
|
One or more Resource Collections describing a set of Resources that should be added to the content of the created jar file. |
|
One or more Resource Collections that should be added to the set of jar libraries that make up the runtime dependency classpath of the application. |
Examples
This section shows two examples of Ant tasks.
<spring-boot:exejar destfile="target/my-application.jar"
classes="target/classes" start-class="com.example.MyApplication">
<resources>
<fileset dir="src/main/resources" />
</resources>
<lib>
<fileset dir="lib" />
</lib>
</spring-boot:exejar>
<exejar destfile="target/my-application.jar" classes="target/classes">
<lib>
<fileset dir="lib" />
</lib>
</exejar>
8.3.2. spring-boot:findmainclass
The findmainclass
task is used internally by exejar
to locate a class declaring a
main
. If necessary, you can also use this task directly in your build. The following
attributes are supported:
Attribute | Description | Required |
---|---|---|
|
The root directory of Java class files |
Yes (unless |
|
Can be used to short-circuit the |
No |
|
The Ant property that should be set with the result |
No (result will be logged if unspecified) |
Examples
This section contains three examples of using findmainclass
.
<findmainclass classesroot="target/classes" />
<findmainclass classesroot="target/classes" property="main-class" />
<findmainclass mainclass="com.example.MainClass" property="main-class" />
8.4. Supporting Other Build Systems
If you want to use a build tool other than Maven, Gradle, or Ant, you likely need to develop your own plugin. Executable jars need to follow a specific format and certain entries need to be written in an uncompressed form (see the “executable jar format” section in the appendix for details).
The Spring Boot Maven and Gradle plugins both make use of spring-boot-loader-tools
to
actually generate jars. If you need to, you may use this library directly.
8.4.1. Repackaging Archives
To repackage an existing archive so that it becomes a self-contained executable archive,
use org.springframework.boot.loader.tools.Repackager
. The Repackager
class takes a
single constructor argument that refers to an existing jar or war archive. Use one of the
two available repackage()
methods to either replace the original file or write to a new
destination. Various settings can also be configured on the repackager before it is run.
8.4.2. Nested Libraries
When repackaging an archive, you can include references to dependency files by using the
org.springframework.boot.loader.tools.Libraries
interface. We do not provide any
concrete implementations of Libraries
here as they are usually build-system-specific.
If your archive already includes libraries, you can use Libraries.NONE
.
8.4.3. Finding a Main Class
If you do not use Repackager.setMainClass()
to specify a main class, the repackager
uses ASM to read class files and tries to find a suitable class with
a public static void main(String[] args)
method. An exception is thrown if more than one
candidate is found.
8.4.4. Example Repackage Implementation
The following example shows a typical repackage implementation:
Repackager repackager = new Repackager(sourceJarFile);
repackager.setBackupSource(false);
repackager.repackage(new Libraries() {
@Override
public void doWithLibraries(LibraryCallback callback) throws IOException {
// Build system specific implementation, callback for each dependency
// callback.library(new Library(nestedFile, LibraryScope.COMPILE));
}
});
8.5. What to Read Next
If you are interested in how the build tool plugins work, you can
look at the spring-boot-tools
module on GitHub. More technical details of the executable jar format are covered in
the appendix.
If you have specific build-related questions, you can check out the “how-to” guides.
9. “How-to” Guides
This section provides answers to some common ‘how do I do that…’ questions that often arise when using Spring Boot. Its coverage is not exhaustive, but it does cover quite a lot.
If you have a specific problem that we do not cover here, you might want to check out
stackoverflow.com to see if someone has
already provided an answer. This is also a great place to ask new questions (please use
the spring-boot
tag).
We are also more than happy to extend this section. If you want to add a ‘how-to’, send us a pull request.
9.1. Spring Boot Application
This section includes topics relating directly to Spring Boot applications.
9.1.1. Create Your Own FailureAnalyzer
FailureAnalyzer
is a great way
to intercept an exception on startup and turn it into a human-readable message, wrapped
in a FailureAnalysis
. Spring
Boot provides such an analyzer for application-context-related exceptions, JSR-303
validations, and more. You can also create your own.
AbstractFailureAnalyzer
is a convenient extension of FailureAnalyzer
that checks the
presence of a specified exception type in the exception to handle. You can extend from
that so that your implementation gets a chance to handle the exception only when it is
actually present. If, for whatever reason, you cannot handle the exception, return null
to give another implementation a chance to handle the exception.
FailureAnalyzer
implementations must be registered in META-INF/spring.factories
.
The following example registers ProjectConstraintViolationFailureAnalyzer
:
org.springframework.boot.diagnostics.FailureAnalyzer=\
com.example.ProjectConstraintViolationFailureAnalyzer
If you need access to the BeanFactory or the Environment , your FailureAnalyzer
can simply implement BeanFactoryAware or EnvironmentAware respectively.
|
9.1.2. Troubleshoot Auto-configuration
The Spring Boot auto-configuration tries its best to “do the right thing”, but sometimes things fail, and it can be hard to tell why.
There is a really useful ConditionEvaluationReport
available in any Spring Boot
ApplicationContext
. You can see it if you enable DEBUG
logging output. If you use
the spring-boot-actuator
(see the Actuator chapter),
there is also a conditions
endpoint that renders the report in JSON. Use that endpoint
to debug the application and see what features have been added (and which have not been
added) by Spring Boot at runtime.
Many more questions can be answered by looking at the source code and the Javadoc. When reading the code, remember the following rules of thumb:
-
Look for classes called
*AutoConfiguration
and read their sources. Pay special attention to the@Conditional*
annotations to find out what features they enable and when. Add--debug
to the command line or a System property-Ddebug
to get a log on the console of all the auto-configuration decisions that were made in your app. In a running Actuator app, look at theconditions
endpoint (/actuator/conditions
or the JMX equivalent) for the same information. -
Look for classes that are
@ConfigurationProperties
(such asServerProperties
) and read from there the available external configuration options. The@ConfigurationProperties
annotation has aname
attribute that acts as a prefix to external properties. Thus,ServerProperties
hasprefix="server"
and its configuration properties areserver.port
,server.address
, and others. In a running Actuator app, look at theconfigprops
endpoint. -
Look for uses of the
bind
method on theBinder
to pull configuration values explicitly out of theEnvironment
in a relaxed manner. It is often used with a prefix. -
Look for
@Value
annotations that bind directly to theEnvironment
. -
Look for
@ConditionalOnExpression
annotations that switch features on and off in response to SpEL expressions, normally evaluated with placeholders resolved from theEnvironment
.
9.1.3. Customize the Environment or ApplicationContext Before It Starts
A SpringApplication
has ApplicationListeners
and ApplicationContextInitializers
that
are used to apply customizations to the context or environment. Spring Boot loads a number
of such customizations for use internally from META-INF/spring.factories
. There is more
than one way to register additional customizations:
-
Programmatically, per application, by calling the
addListeners
andaddInitializers
methods onSpringApplication
before you run it. -
Declaratively, per application, by setting the
context.initializer.classes
orcontext.listener.classes
properties. -
Declaratively, for all applications, by adding a
META-INF/spring.factories
and packaging a jar file that the applications all use as a library.
The SpringApplication
sends some special ApplicationEvents
to the listeners (some
even before the context is created) and then registers the listeners for events published
by the ApplicationContext
as well. See
“Application Events and Listeners” in the
‘Spring Boot features’ section for a complete list.
It is also possible to customize the Environment
before the application context is
refreshed by using EnvironmentPostProcessor
. Each implementation should be registered in
META-INF/spring.factories
, as shown in the following example:
org.springframework.boot.env.EnvironmentPostProcessor=com.example.YourEnvironmentPostProcessor
The implementation can load arbitrary files and add them to the Environment
. For
instance, the following example loads a YAML configuration file from the classpath:
public class EnvironmentPostProcessorExample implements EnvironmentPostProcessor {
private final YamlPropertySourceLoader loader = new YamlPropertySourceLoader();
@Override
public void postProcessEnvironment(ConfigurableEnvironment environment, SpringApplication application) {
Resource path = new ClassPathResource("com/example/myapp/config.yml");
PropertySource<?> propertySource = loadYaml(path);
environment.getPropertySources().addLast(propertySource);
}
private PropertySource<?> loadYaml(Resource path) {
if (!path.exists()) {
throw new IllegalArgumentException("Resource " + path + " does not exist");
}
try {
return this.loader.load("custom-resource", path).get(0);
}
catch (IOException ex) {
throw new IllegalStateException("Failed to load yaml configuration from " + path, ex);
}
}
}
The Environment has already been prepared with all the usual property sources
that Spring Boot loads by default. It is therefore possible to get the location of the
file from the environment. The preceding example adds the custom-resource property
source at the end of the list so that a key defined in any of the usual other locations
takes precedence. A custom implementation may define another order.
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While using @PropertySource on your @SpringBootApplication may seem to be a
convenient and easy way to load a custom resource in the Environment , we do not
recommend it, because Spring Boot prepares the Environment before the
ApplicationContext is refreshed. Any key defined with @PropertySource is loaded too
late to have any effect on auto-configuration.
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9.1.4. Build an ApplicationContext Hierarchy (Adding a Parent or Root Context)
You can use the ApplicationBuilder
class to create parent/child ApplicationContext
hierarchies. See “Fluent Builder API”
in the ‘Spring Boot features’ section for more information.
9.1.5. Create a Non-web Application
Not all Spring applications have to be web applications (or web services). If you want to
execute some code in a main
method but also bootstrap a Spring application to set up
the infrastructure to use, you can use the SpringApplication
features of Spring
Boot. A SpringApplication
changes its ApplicationContext
class, depending on whether
it thinks it needs a web application or not. The first thing you can do to help it is to
leave server-related dependencies (e.g. servlet API) off the classpath. If you cannot do
that (for example, you run two applications from the same code base) then you can
explicitly call setWebApplicationType(WebApplicationType.NONE)
on your
SpringApplication
instance or set the applicationContextClass
property (through the
Java API or with external properties). Application code that you want to run as your
business logic can be implemented as a CommandLineRunner
and dropped into the context as
a @Bean
definition.
9.2. Properties and Configuration
This section includes topics about setting and reading properties and configuration settings and their interaction with Spring Boot applications.
9.2.1. Automatically Expand Properties at Build Time
Rather than hardcoding some properties that are also specified in your project’s build configuration, you can automatically expand them by instead using the existing build configuration. This is possible in both Maven and Gradle.
Automatic Property Expansion Using Maven
You can automatically expand properties from the Maven project by using resource
filtering. If you use the spring-boot-starter-parent
, you can then refer to your
Maven ‘project properties’ with @..@
placeholders, as shown in the following example:
Only production configuration is filtered that way (in other words, no filtering is
applied on src/test/resources ).
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If you enable the addResources flag, the spring-boot:run goal can add
src/main/resources directly to the classpath (for hot reloading purposes). Doing so
circumvents the resource filtering and this feature. Instead, you can use the exec:java
goal or customize the plugin’s configuration. See the
plugin usage page for more details.
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If you do not use the starter parent, you need to include the following element inside
the <build/>
element of your pom.xml
:
<resources>
<resource>
<directory>src/main/resources</directory>
<filtering>true</filtering>
</resource>
</resources>
You also need to include the following element inside <plugins/>
:
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-resources-plugin</artifactId>
<version>2.7</version>
<configuration>
<delimiters>
<delimiter>@</delimiter>
</delimiters>
<useDefaultDelimiters>false</useDefaultDelimiters>
</configuration>
</plugin>
The useDefaultDelimiters property is important if you use standard Spring
placeholders (such as ${placeholder} ) in your configuration. If that property is not
set to false , these may be expanded by the build.
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Automatic Property Expansion Using Gradle
You can automatically expand properties from the Gradle project by configuring the
Java plugin’s processResources
task to do so, as shown in the following example:
processResources {
expand(project.properties)
}
You can then refer to your Gradle project’s properties by using placeholders, as shown in the following example:
app.name=${name}
app.description=${description}
Gradle’s expand method uses Groovy’s SimpleTemplateEngine , which transforms
${..} tokens. The ${..} style conflicts with Spring’s own property placeholder
mechanism. To use Spring property placeholders together with automatic expansion, escape
the Spring property placeholders as follows: \${..} .
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9.2.2. Externalize the Configuration of SpringApplication
A SpringApplication
has bean properties (mainly setters), so you can use its Java API as
you create the application to modify its behavior. Alternatively, you can externalize the
configuration by setting properties in spring.main.*
. For example, in
application.properties
, you might have the following settings:
spring.main.web-application-type=none
spring.main.banner-mode=off
Then the Spring Boot banner is not printed on startup, and the application is not starting an embedded web server.
Properties defined in external configuration override the values specified with the Java
API, with the notable exception of the sources used to create the ApplicationContext
.
Consider the following application:
new SpringApplicationBuilder()
.bannerMode(Banner.Mode.OFF)
.sources(demo.MyApp.class)
.run(args);
Now consider the following configuration:
spring.main.sources=com.acme.Config,com.acme.ExtraConfig
spring.main.banner-mode=console
The actual application now shows the banner (as overridden by configuration) and uses
three sources for the ApplicationContext
(in the following order): demo.MyApp
,
com.acme.Config
, and com.acme.ExtraConfig
.
9.2.3. Change the Location of External Properties of an Application
By default, properties from different sources are added to the Spring Environment
in a
defined order (see “Externalized Configuration” in
the ‘Spring Boot features’ section for the exact order).
A nice way to augment and modify this ordering is to add @PropertySource
annotations to your
application sources. Classes passed to the SpringApplication
static convenience
methods and those added using setSources()
are inspected to see if they have
@PropertySources
. If they do, those properties are added to the Environment
early
enough to be used in all phases of the ApplicationContext
lifecycle. Properties added
in this way have lower priority than any added by using the default locations (such as
application.properties
), system properties, environment variables, or the command line.
You can also provide the following System properties (or environment variables) to change the behavior:
-
spring.config.name
(SPRING_CONFIG_NAME
): Defaults toapplication
as the root of the file name. -
spring.config.location
(SPRING_CONFIG_LOCATION
): The file to load (such as a classpath resource or a URL). A separateEnvironment
property source is set up for this document and it can be overridden by system properties, environment variables, or the command line.
No matter what you set in the environment, Spring Boot always loads
application.properties
as described above. By default, if YAML is used, then files with
the ‘.yml’ extension are also added to the list.
Spring Boot logs the configuration files that are loaded at the DEBUG
level and the
candidates it has not found at TRACE
level.
See ConfigFileApplicationListener
for more detail.
9.2.4. Use ‘Short’ Command Line Arguments
Some people like to use (for example) --port=9000
instead of --server.port=9000
to
set configuration properties on the command line. You can enable this behavior by using
placeholders in application.properties
, as shown in the following example:
server.port=${port:8080}
If you inherit from the spring-boot-starter-parent POM, the default filter
token of the maven-resources-plugins has been changed from ${*} to @ (that is,
@maven.token@ instead of ${maven.token} ) to prevent conflicts with Spring-style
placeholders. If you have enabled Maven filtering for the application.properties
directly, you may want to also change the default filter token to use
other
delimiters.
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In this specific case, the port binding works in a PaaS environment such as Heroku
or Cloud Foundry. In those two platforms, the PORT environment variable is set
automatically and Spring can bind to capitalized synonyms for Environment properties.
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9.2.5. Use YAML for External Properties
YAML is a superset of JSON and, as such, is a convenient syntax for storing external properties in a hierarchical format, as shown in the following example:
spring:
application:
name: cruncher
datasource:
driverClassName: com.mysql.jdbc.Driver
url: jdbc:mysql://localhost/test
server:
port: 9000
Create a file called application.yml
and put it in the root of your classpath.
Then add snakeyaml
to your dependencies (Maven coordinates org.yaml:snakeyaml
, already
included if you use the spring-boot-starter
). A YAML file is parsed to a Java
Map<String,Object>
(like a JSON object), and Spring Boot flattens the map so that it
is one level deep and has period-separated keys, as many people are used to with
Properties
files in Java.
The preceding example YAML corresponds to the following application.properties
file:
spring.application.name=cruncher
spring.datasource.driverClassName=com.mysql.jdbc.Driver
spring.datasource.url=jdbc:mysql://localhost/test
server.port=9000
See “Using YAML Instead of Properties” in the ‘Spring Boot features’ section for more information about YAML.
9.2.6. Set the Active Spring Profiles
The Spring Environment
has an API for this, but you would normally set a System property
(spring.profiles.active
) or an OS environment variable (SPRING_PROFILES_ACTIVE
).
Also, you can launch your application with a -D
argument (remember to put it before the
main class or jar archive), as follows:
$ java -jar -Dspring.profiles.active=production demo-0.0.1-SNAPSHOT.jar
In Spring Boot, you can also set the active profile in application.properties
, as shown
in the following example:
spring.profiles.active=production
A value set this way is replaced by the System property or environment variable setting
but not by the SpringApplicationBuilder.profiles()
method. Thus, the latter Java API can
be used to augment the profiles without changing the defaults.
See “Profiles” in the “Spring Boot features” section for more information.
9.2.7. Change Configuration Depending on the Environment
A YAML file is actually a sequence of documents separated by ---
lines, and each
document is parsed separately to a flattened map.
If a YAML document contains a spring.profiles
key, then the profiles value
(a comma-separated list of profiles) is fed into the Spring
Environment.acceptsProfiles()
method. If any of those profiles is active, that document
is included in the final merge (otherwise, it is not), as shown in the following example:
serv