2.1.18.RELEASE
Copyright © 2012-2020
Table of Contents
RestTemplate
WebClient
settings.xml
SpringApplication
persistence.xml
Filespring-boot-antlib
This section provides a brief overview of Spring Boot reference documentation. It serves as a map for the rest of the document.
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.
If you have trouble with Spring Boot, we would like to help.
spring-boot
.Note | |
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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. |
Instructions for how to upgrade from earlier versions of Spring Boot are provided on the project wiki. Follow the links in the in the release notes section to find the version that you want to upgrade to.
Upgrading instructions are always the first item in the release notes. If you are more than one release behind, please make sure that you also review the release notes of the versions that you jumped.
You should always ensure that you are running a supported version of Spring Boot.
If you are getting started with Spring Boot or 'Spring' in general, start with the following topics:
Ready to actually start using Spring Boot? We have you covered:
Need more details about Spring Boot’s core features? The following content is for you:
When you are ready to push your Spring Boot application to production, we have some tricks that you might like:
Finally, we have a few topics for more advanced users:
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.
Spring Boot helps you 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:
Spring Boot 2.1.18.RELEASE requires Java 8 and is compatible up to Java 12 (included). Spring Framework 5.1.19.RELEASE or above is also required.
Explicit build support is provided for the following build tools:
Build Tool | Version |
---|---|
Maven | 3.3+ |
Gradle | 4.x (4.4 and later) and 5.x |
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.
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).
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.
Tip | |
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On many operating systems, Maven can be installed with a package manager.
If you use OSX Homebrew, try |
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>2.1.18.RELEASE</version> </parent> <!-- Override inherited settings --> <description/> <developers> <developer/> </developers> <licenses> <license/> </licenses> <scm> <url/> </scm> <url/> <!-- 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> </project>
Tip | |
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The |
Spring Boot is compatible with Gradle 4.x (4.4 and later) and 5.x. 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.
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.
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).
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 v2.1.18.RELEASE
If you develop features for the CLI and want 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-2.1.18.RELEASE-bin/spring-2.1.18.RELEASE/ $ sdk default springboot dev $ spring --version Spring CLI v2.1.18.RELEASE
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 * 2.1.18.RELEASE ================================================================================ + - local version * - installed > - currently in use ================================================================================
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
.
Note | |
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If you do not see the formula, your installation of brew might be out-of-date.
In that case, run |
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
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
Note | |
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If you install the Spring Boot CLI by using Homebrew or MacPorts, the command-line completion scripts are automatically registered with your shell. |
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
.
Note | |
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If you do not see the app manifest, your installation of scoop might be out-of-date.
In that case, run |
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
Note | |
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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!
If you are upgrading from the 1.x
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>
Warning | |
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Properties that are added late to the environment, such as when using |
Note | |
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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
).
If you manually installed the CLI, follow the standard instructions, remembering to update your PATH
environment variable to remove any older references.
This section describes how to develop a small “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.
Tip | |
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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
Note | |
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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. |
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>2.1.18.RELEASE</version> </parent> <description/> <developers> <developer/> </developers> <licenses> <license/> </licenses> <scm> <url/> </scm> <url/> <!-- Additional lines to be added here... --> </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).
Note | |
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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. |
Spring Boot provides a number of “Starters” that let you add jars to your classpath.
Our sample application has already used 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.
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 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.
Tip | |
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The |
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 final part of our application is the main
method.
This is 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.
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 :: (v2.1.18.RELEASE) ....... . . . ....... . . . (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
.
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>
Note | |
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The |
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:2.1.18.RELEASE: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 :: (v2.1.18.RELEASE) ....... . . . ....... . . . (log output here) ....... . . . ........ Started Example in 2.536 seconds (JVM running for 2.864)
As before, to exit the application, press ctrl-c
.
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.
The Spring Boot repository also has a bunch of samples you can run. The samples are independent of the rest of the code (that is, you do not need to build the rest to run or use the samples).
Otherwise, the next logical step is to read Part III, “Using Spring Boot”. If you are really impatient, you could also jump ahead and read about Spring Boot features.
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.
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.
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.
Note | |
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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.
Warning | |
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Each release of Spring Boot is associated with a base version of the Spring Framework. We highly recommend that you not specify its version. |
Maven users can inherit from the spring-boot-starter-parent
project to obtain sensible defaults.
The parent project provides the following features:
repackage
goal with a repackage
execution id.application.properties
and application.yml
including profile-specific files (for example, application-dev.properties
and application-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
.)
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>2.1.18.RELEASE</version> </parent>
Note | |
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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>
Tip | |
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Check the |
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>2.1.18.RELEASE</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>2.1.18.RELEASE</version> <type>pom</type> <scope>import</scope> </dependency> </dependencies> </dependencyManagement>
Note | |
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In the preceding example, we specify a BOM, but any dependency type can be overridden in the same way. |
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>
Note | |
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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. |
To learn about using Spring Boot with Gradle, please refer to the documentation for Spring Boot’s Gradle plugin:
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="2.1.18.RELEASE" /> <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>
Tip | |
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If you do not want to use the |
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:
Table 14.1. Spring Boot application starters
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 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:
Table 14.2. Spring Boot production starters
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:
Table 14.3. Spring Boot technical starters
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 |
Tip | |
---|---|
For a list of additional community contributed starters, see the README file in the |
Spring Boot does not require any specific code layout to work. However, there are some best practices that help.
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
, @EntityScan
, or @SpringBootApplication
annotations, since every class from every jar is read.
Tip | |
---|---|
We recommend that you follow Java’s recommended package naming conventions and use a reversed domain name (for example, |
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.
Tip | |
---|---|
If you don’t want to use |
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); } }
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
.
Tip | |
---|---|
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 |
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.
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.
Tip | |
---|---|
You should only ever add one |
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.
If you find that specific auto-configuration classes that you do not want are being applied, you can use the exclude attribute of @SpringBootApplication
to disable them, as shown in the following example:
import org.springframework.boot.autoconfigure.*; import org.springframework.boot.autoconfigure.jdbc.*; @SpringBootApplication(exclude={DataSourceAutoConfiguration.class}) public class MyApplication { }
If the class is not on the classpath, you can use the excludeName
attribute of the annotation and specify the fully qualified name instead.
If you prefer to use @EnableAutoConfiguration
rather than @SpringBootApplication
, exclude
and excludeName
are also available.
Finally, you can also control the list of auto-configuration classes to exclude by using the spring.autoconfigure.exclude
property.
Tip | |
---|---|
You can define exclusions both at the annotation level and by using the property. |
Note | |
---|---|
Even though auto-configuration classes are |
You are free to use any of the standard Spring Framework techniques to define your beans and their injected dependencies.
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; } // ... }
Tip | |
---|---|
Notice how using constructor injection lets the |
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)@Configuration
: allow to register extra beans in the context or import additional configuration classesThe @SpringBootApplication
annotation is equivalent to using @Configuration
, @EnableAutoConfiguration
, and @ComponentScan
with their default attributes, as shown in the following example:
package com.example.myapplication; import org.springframework.boot.SpringApplication; import org.springframework.boot.autoconfigure.SpringBootApplication; @SpringBootApplication // same as @Configuration @EnableAutoConfiguration @ComponentScan public class Application { public static void main(String[] args) { SpringApplication.run(Application.class, args); } }
Note | |
---|---|
|
Note | |
---|---|
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 in your application: package com.example.myapplication; import org.springframework.boot.SpringApplication; import org.springframework.context.annotation.ComponentScan import org.springframework.context.annotation.Configuration; import org.springframework.context.annotation.Import; @Configuration @EnableAutoConfiguration @Import({ MyConfig.class, MyAnotherConfig.class }) public class Application { public static void main(String[] args) { SpringApplication.run(Application.class, args); } } In this example, |
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. The sample applies to debugging Spring Boot applications. You do not need any special IDE plugins or extensions.
Note | |
---|---|
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. |
You can run a Spring Boot application from your IDE as a 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.
Tip | |
---|---|
If you accidentally run a web application twice, you see a “Port already in use” error.
STS users can use the |
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
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
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
Since Spring Boot applications are 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 Chapter 21, Developer Tools section later in this chapter and the Hot swapping “How-to” for details.
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:
Maven.
<dependencies> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-devtools</artifactId> <optional>true</optional> </dependency> </dependencies>
Gradle.
configurations {
developmentOnly
runtimeClasspath {
extendsFrom developmentOnly
}
}
dependencies {
developmentOnly("org.springframework.boot:spring-boot-devtools")
}
Note | |
---|---|
Developer tools are automatically disabled when running a fully packaged application.
If your application is launched from |
Tip | |
---|---|
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. |
Tip | |
---|---|
Repackaged archives do not contain devtools by default.
If you want to use a certain remote devtools feature, you need to disable the |
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.
Note | |
---|---|
If you don’t want property defaults to be applied you can set |
Tip | |
---|---|
For a complete list of the properties that are applied by the devtools, see DevToolsPropertyDefaultsPostProcessor. |
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.
Note | |
---|---|
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, Gradle and Maven do that when they detect DevTools on the classpath. |
Tip | |
---|---|
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. |
Note | |
---|---|
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 ( |
Note | |
---|---|
When deciding if an entry on the classpath should trigger a restart when it changes, DevTools automatically ignores projects named |
Note | |
---|---|
DevTools needs to customize the |
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
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/**
Tip | |
---|---|
If you want to keep those defaults and add additional exclusions, use the |
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.
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); }
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.
Note | |
---|---|
Any update to the file will trigger a check, but restart only actually occurs if Devtools has detected it has something to do. |
To use a trigger file, set the spring.devtools.restart.trigger-file
property to the name (excluding any path) of your trigger file.
The trigger file must appear somewhere on your classpath.
For example, if you have a project with the following structure:
src +- main +- resources +- .reloadtrigger
Then your trigger-file
property would be:
spring.devtools.restart.trigger-file=.reloadtrigger
Restarts will now only happen when the src/main/resources/.reloadtrigger
is updated.
Tip | |
---|---|
You might want to set |
Some IDEs have features that save you from needing to update your trigger file manually.
Spring Tools for Eclipse and IntelliJ IDEA (Ultimate Edition) both have such support.
With Spring Tools, you can use the “reload” button from the console view (as long as your trigger-file
is named .reloadtrigger
).
For IntelliJ, you can follow the instructions in their documentation.
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
Note | |
---|---|
All property keys must be unique.
As long as a property starts with |
Tip | |
---|---|
All |
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.
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
.
Note | |
---|---|
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. |
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-boot-devtools.properties.
spring.devtools.reload.trigger-file=.reloadtrigger
Note | |
---|---|
Profiles are not supported in devtools properties/yaml files. Any profiles activated in |
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 as enabling it can be a security risk. It should only be enabled when running on a trusted network or when secured with SSL. If neither of these options is available to you, you should not use DevTools' remote support. You should never enable support on a production deployment.
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 the spring.devtools.remote.secret
property.
Like any important password or secret, the value should be unique and strong such that it cannot be guessed or brute-forced.
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.
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:
Run Configurations…
from the Run
menu.Java Application
“launch configuration”.my-app
project.org.springframework.boot.devtools.RemoteSpringApplication
as the main class.https://myapp.cfapps.io
to the Program arguments
(or whatever your remote URL is).A running remote client might resemble the following listing:
. ____ _ __ _ _ /\\ / ___'_ __ _ _(_)_ __ __ _ ___ _ \ \ \ \ ( ( )\___ | '_ | '_| | '_ \/ _` | | _ \___ _ __ ___| |_ ___ \ \ \ \ \\/ ___)| |_)| | | | | || (_| []::::::[] / -_) ' \/ _ \ _/ -_) ) ) ) ) ' |____| .__|_| |_|_| |_\__, | |_|_\___|_|_|_\___/\__\___|/ / / / =========|_|==============|___/===================================/_/_/_/ :: Spring Boot Remote :: 2.1.18.RELEASE 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)
Note | |
---|---|
Because the remote client is using the same classpath as the real application it can directly read application properties.
This is how the |
Tip | |
---|---|
It is always advisable to use |
Tip | |
---|---|
If you need to use a proxy to access the remote application, configure the |
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.
Note | |
---|---|
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. |
FileSystemWatcher works by polling the class changes with a certain time interval, and then waiting for a predefined quiet period to make sure there are no more changes. The changes are then uploaded to the remote application. On a slower development environment, it may happen that the quiet period is not enough, and the changes in the classes may be split into batches. The server is restarted after the first batch of class changes is uploaded. The next batch can’t be sent to the application, since the server is restarting.
This is typically manifested by a warning in the RemoteSpringApplication
logs about failing to upload some of the classes, and a consequent retry.
But it may also lead to application code inconsistency and failure to restart after the first batch of changes is uploaded.
If you observe such problems constantly, try increasing the spring.devtools.restart.poll-interval
and spring.devtools.restart.quiet-period
parameters to the values that fit your development environment:
spring.devtools.restart.poll-interval=2s spring.devtools.restart.quiet-period=1s
The monitored classpath folders are now polled every 2 seconds for changes, and a 1 second quiet period is maintained to make sure there are no additional class changes.
If you have Spring Security on the classpath, you may observe HTTP error 401 or 403 in the logs of the RemoteSpringApplication
:
Exception in thread "File Watcher" java.lang.IllegalStateException: Unexpected 401 UNAUTHORIZED response uploading class files
The URL for class uploading should be exempted both from the web security and from the csrf filter. The following example shows how anonymous access to the remote devtools endpoint can be configured:
@Configuration public class SecurityConfiguration extends WebSecurityConfigurerAdapter { @Override protected void configure(HttpSecurity http) throws Exception { http.requestMatchers("/.~~spring-boot!~/restart").anyRequest().anonymous() .and().csrf().disable(); } }
Note | |
---|---|
The above configuration will only affect the remote devtools endpoint. Spring Boot’s default security auto-configuration will still apply to the rest of the application. If the rest of the application requires custom security, it needs to be configured separately. |
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 Part V, “Spring Boot Actuator: Production-ready features” for details.
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.
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 "Part II, “Getting Started”" and "Part III, “Using Spring Boot”" sections, so that you have a good grounding of the basics.
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 :: v2.1.18.RELEASE 2019-04-31 13:09:54.117 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) 2019-04-31 13:09:54.166 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 2019-04-01 13:09:56.912 INFO 41370 --- [ main] .t.TomcatServletWebServerFactory : Server initialized with port: 8080 2019-04-01 13:09:57.501 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 Section 27.4, “Log Levels”.
The application version is determined using the implementation version from the main application class’s package.
Startup information logging can be turned off by setting spring.main.log-startup-info
to false
.
This will also turn off logging of the application’s active profiles.
Tip | |
---|---|
To add additional logging during startup, you can override |
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.
Note | |
---|---|
Spring Boot provides numerous |
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
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:
Table 24.1. Banner variables
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 |
Tip | |
---|---|
The |
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
.
Note | |
---|---|
YAML maps spring: main: banner-mode: "off" |
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); }
Note | |
---|---|
The constructor arguments passed to |
It is also possible to configure the SpringApplication
by using an application.properties
file.
See Chapter 25, Externalized Configuration for details.
For a complete list of the configuration options, see the SpringApplication
Javadoc.
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);
Note | |
---|---|
There are some restrictions when creating an |
In addition to the usual Spring Framework events, such as ContextRefreshedEvent
, a SpringApplication
sends some additional application events.
Note | |
---|---|
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:
ApplicationStartingEvent
is sent at the start of a run but before any processing, except for the registration of listeners and initializers.ApplicationEnvironmentPreparedEvent
is sent when the Environment
to be used in the context is known but before the context is created.ApplicationPreparedEvent
is sent just before the refresh is started but after bean definitions have been loaded.ApplicationStartedEvent
is sent after the context has been refreshed but before any application and command-line runners have been called.ApplicationReadyEvent
is sent after any application and command-line runners have been called.
It indicates that the application is ready to service requests.ApplicationFailedEvent
is sent if there is an exception on startup.Tip | |
---|---|
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
.
A SpringApplication
attempts to create the right type of ApplicationContext
on your behalf.
The algorithm used to determine a WebApplicationType
is the following:
AnnotationConfigServletWebServerApplicationContext
is usedAnnotationConfigReactiveWebServerApplicationContext
is usedAnnotationConfigApplicationContext
is usedThis 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(…)
.
Tip | |
---|---|
It is often desirable to call |
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"] } }
Tip | |
---|---|
Spring Boot also registers a |
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 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.
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.
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.
Tip | |
---|---|
If you want to know on which HTTP port the application is running, get the property with a key of |
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:
~/.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.SPRING_APPLICATION_JSON
(inline JSON embedded in an environment variable or system property).ServletConfig
init parameters.ServletContext
init parameters.java:comp/env
.System.getProperties()
).RandomValuePropertySource
that has properties only in random.*
.application-{profile}.properties
and YAML variants).application-{profile}.properties
and YAML variants).application.properties
and YAML variants).application.properties
and YAML variants).@PropertySource
annotations on your @Configuration
classes.
Please note that such property sources are not added to the Environment
until the application context is being refreshed.
This is too late to configure certain properties such as logging.*
and spring.main.*
which are read before refresh begins.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("${name}") private String name; // ... }
On your application classpath (for example, inside your jar) you can have an application.properties
file that provides a sensible default property value for name
.
When running in a new environment, an application.properties
file can be provided outside of your jar that overrides the name
.
For one-off testing, you can launch with a specific command line switch (for example, java -jar app.jar --name="Spring"
).
The RandomValuePropertySource
is useful for injecting random values (for example, into secrets or test cases).
It can produce integers, longs, uuids, or strings, as shown in the following example:
my.secret=${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).
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)
.
SpringApplication
loads properties from application.properties
files in the following locations and adds them to the Spring Environment
:
/config
subdirectory of the current directory/config
packageThe list is ordered by precedence (properties defined in locations higher in the list override those defined in lower locations).
Note | |
---|---|
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
Warning | |
---|---|
|
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.
Note | |
---|---|
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, |
Note | |
---|---|
If your application runs in a container, then JNDI properties (in |
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.
Note | |
---|---|
If you have specified any files in |
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
Tip | |
---|---|
You can also use this technique to create “short” variants of existing Spring Boot properties. See the Section 78.4, “Use ‘Short’ Command Line Arguments” how-to for details. |
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 Section 77.3, “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.
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.
Note | |
---|---|
If you use “Starters”, SnakeYAML is automatically provided by |
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; } }
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.
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
.
Note | |
---|---|
|
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 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:
application-dev.yml.
server: port: 8000 --- spring: profiles: "!test" security: user: password: "secret"
If you run the application with the arguments --spring.profiles.active=dev" you might expect `security.user.password
to be set to “secret”, but this is not the case.
The nested document will be filtered because the main file is named application-dev.yml
.
It is already considered to be profile-specific, and nested documents will be ignored.
Tip | |
---|---|
We recommend that you don’t mix profile-specific YAML files and multiple YAML documents. Stick to using only one of them. |
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, 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 of false
by default.acme.remote-address
, with a type that can be coerced from String
.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 been SecurityProperties
.acme.security.password
.acme.security.roles
, with a collection of String
.Note | |
---|---|
The properties that map to |
Note | |
---|---|
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. |
Tip | |
---|---|
See also the differences between |
You also need to list the properties classes to register in the @EnableConfigurationProperties
annotation, as shown in the following example:
@Configuration @EnableConfigurationProperties(AcmeProperties.class) public class MyConfiguration { }
Note | |
---|---|
When the The bean name in the example above is |
The preceding configuration creates a regular bean for AcmeProperties
.
We recommend that @ConfigurationProperties
only deal with the environment and, in particular, does not inject other beans from the context.
Keep in mind that the @EnableConfigurationProperties
annotation is also automatically applied to your project so that any existing bean annotated with @ConfigurationProperties
is configured from the Environment
.
Instead of annotating MyConfiguration
with @EnableConfigurationProperties(AcmeProperties.class)
, you could make AcmeProperties
a bean, as shown in the following example:
@Component @ConfigurationProperties(prefix="acme") public class AcmeProperties { // ... see the preceding example }
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()); // ... } }
Tip | |
---|---|
Using |
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 property defined with the another
prefix is mapped onto that AnotherComponent
bean in manner similar to the preceding AcmeProperties
example.
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
).
As an 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; } }
With the preceding code, the following properties names can all be used:
Table 25.1. relaxed binding
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. |
Note | |
---|---|
The |
Table 25.2. relaxed binding rules per property source
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 (see the section called “Binding from Environment Variables”). | Numeric values surrounded by underscores (see the section called “Binding from Environment Variables”)` |
System properties | Camel case, kebab case, or underscore notation | Standard list syntax using |
Tip | |
---|---|
We recommend that, when possible, properties are stored in lower-case kebab format, such as |
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.
Note | |
---|---|
For YAML files, the brackets need to be surrounded by quotes for the keys to be parsed properly. |
Most operating systems impose strict rules around the names that can be used for environment variables.
For example, Linux shell variables can contain only letters (a
to z
or A
to Z
), numbers (0
to 9
) or the underscore character (_
).
By convention, Unix shell variables will also have their names in UPPERCASE.
Spring Boot’s relaxed binding rules are, as much as possible, designed to be compatible with these naming restrictions.
To convert a property name in the canonical-form to an environment variable name you can follow these rules:
.
) with underscores (_
).-
).For example, the configuration property spring.main.log-startup-info
would be an environment variable named SPRING_MAIN_LOGSTARTUPINFO
.
Note | |
---|---|
Underscores cannot be used to replace the dashes in property names.
If you attempt to use |
Environment variables can also be used when binding to object lists.
To bind to a List
, the element number should be surrounded with underscores in the variable name.
For example, the configuration property my.acme[0].other
would use an environment variable named MY_ACME_0_OTHER
.
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
).
Note | |
---|---|
The preceding merging rules apply to properties from all property sources and not just YAML files. |
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
).
Note | |
---|---|
As this bean is requested very early during the application lifecycle, make sure to limit the dependencies that your |
Spring Boot has dedicated support for expressing durations.
If you expose a java.time.Duration
property, the following formats in application properties are available:
long
representation (using milliseconds as the default unit unless a @DurationUnit
has been specified)java.time.Duration
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 nanosecondsus
for microsecondsms
for millisecondss
for secondsm
for minutesh
for hoursd
for daysThe default unit is milliseconds and can be overridden using @DurationUnit
as illustrated in the sample above.
Tip | |
---|---|
If you are upgrading from a previous version that is using |
Spring Framework has a DataSize
value type that expresses a size in bytes.
If you expose a DataSize
property, the following formats in application properties are available:
long
representation (using bytes as the default unit unless a @DataSizeUnit
has been specified)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 bytesKB
for kilobytesMB
for megabytesGB
for gigabytesTB
for terabytesThe default unit is bytes and can be overridden using @DataSizeUnit
as illustrated in the sample above.
Tip | |
---|---|
If you are upgrading from a previous version that is using |
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 }
Tip | |
---|---|
You can also trigger validation by annotating the |
To ensure that validation is always triggered for nested properties, even when no properties are found, the associated field must be annotated with @Valid
.
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.
There is a property validation sample that shows how to set things up.
Tip | |
---|---|
The |
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 | Limited (see note below) | |
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
.
Doing so will provide you with structured, type-safe object that you can inject into your own beans.
If you do want to use @Value
, we recommend that you refer to property names using their canonical form (kebab-case using only lowercase letters).
This will allow Spring Boot to use the same logic as it does when relaxed binding @ConfigurationProperties
.
For example, @Value("{demo.item-price}")
will pick up demo.item-price
and demo.itemPrice
forms from the application.properties
file, as well as DEMO_ITEMPRICE
from the system environment.
If you used @Value("{demo.itemPrice}")
instead, demo.item-price
and DEMO_ITEMPRICE
would not be considered.
Finally, while you can write a SpEL
expression in @Value
, such expressions are not processed from application property files.
Spring Profiles provide a way to segregate parts of your application configuration and make it be available only in certain environments.
Any @Component
or @Configuration
can be marked with @Profile
to limit when it is loaded, as shown in the following example:
@Configuration @Profile("production") public class ProductionConfiguration { // ... }
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
.
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
Note | |
---|---|
Remember that the |
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.
Profile-specific variants of both application.properties
(or application.yml
) and files referenced through @ConfigurationProperties
are considered as files and loaded.
See "Section 25.4, “Profile-specific Properties”" for details.
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.
Tip | |
---|---|
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. |
Tip | |
---|---|
When you deploy your application to a servlet container or application server, logging performed via the Java Util Logging API is not routed into your application’s logs. This prevents logging performed by the container or other applications that have been deployed to it from appearing in your application’s logs. |
The default log output from Spring Boot resembles the following example:
2019-03-05 10:57:51.112 INFO 45469 --- [ main] org.apache.catalina.core.StandardEngine : Starting Servlet Engine: Apache Tomcat/7.0.52 2019-03-05 10:57:51.253 INFO 45469 --- [ost-startStop-1] o.a.c.c.C.[Tomcat].[localhost].[/] : Initializing Spring embedded WebApplicationContext 2019-03-05 10:57:51.253 INFO 45469 --- [ost-startStop-1] o.s.web.context.ContextLoader : Root WebApplicationContext: initialization completed in 1358 ms 2019-03-05 10:57:51.698 INFO 45469 --- [ost-startStop-1] o.s.b.c.e.ServletRegistrationBean : Mapping servlet: 'dispatcherServlet' to [/] 2019-03-05 10:57:51.702 INFO 45469 --- [ost-startStop-1] o.s.b.c.embedded.FilterRegistrationBean : Mapping filter: 'hiddenHttpMethodFilter' to: [/*]
The following items are output:
ERROR
, WARN
, INFO
, DEBUG
, or TRACE
.---
separator to distinguish the start of actual log messages.Note | |
---|---|
Logback does not have a |
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
Note | |
---|---|
You can also specify |
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).
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
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
or logging.path
property (for example, in your application.properties
).
The following table shows how the logging.*
properties can be used together:
Table 27.1. Logging properties
logging.file | logging.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.
Note | |
---|---|
The logging system is initialized early in the application lifecycle.
Consequently, logging properties are not found in property files loaded through |
Tip | |
---|---|
Logging properties are independent of the actual logging infrastructure.
As a result, specific configuration keys (such as |
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
It’s also possible to set logging levels using environment variables.
For example, LOGGING_LEVEL_ORG_SPRINGFRAMEWORK_WEB=DEBUG
will set org.springframework.web
to DEBUG
.
Note | |
---|---|
The above approach will only work for package level logging. Since relaxed binding always converts environment variables to lowercase, it’s not possible to configure logging for an individual class in this way. If you need to configure logging for a class, you can use the SPRING_APPLICATION_JSON variable. |
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 |
|
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
.
Note | |
---|---|
Since logging is initialized before the |
Depending on your logging system, the following files are loaded:
Logging System | Customization |
---|---|
Logback |
|
Log4j2 |
|
JDK (Java Util Logging) |
|
Note | |
---|---|
When possible, we recommend that you use the |
Warning | |
---|---|
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. |
|
| 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. |
|
| 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:
Tip | |
---|---|
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 |
Tip | |
---|---|
You can add MDC and other ad-hoc content to log lines by overriding only the 2019-08-30 12:30:04.031 user:someone INFO 22174 --- [ nio-8080-exec-0] demo.Controller Handling authenticated request |
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.
Note | |
---|---|
Because the standard |
Warning | |
---|---|
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]]
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 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>
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>
Note | |
---|---|
The |
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.
Note | |
---|---|
The auto-configuration applies when the default properties file for the configured resource bundle is available (i.e. |
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
Tip | |
---|---|
|
See MessageSourceProperties
for more supported options.
Spring Boot provides integration with three JSON mapping libraries:
Jackson is the preferred and default library.
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
.
Auto-configuration for Gson is provided.
When Gson is on the classpath a Gson
bean is automatically configured.
Several spring.gson.*
configuration properties are provided for customizing the configuration.
To take more control, one or more GsonBuilderCustomizer
beans can be used.
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.
The Spring Web MVC framework (often referred to as “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 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:
ContentNegotiatingViewResolver
and BeanNameViewResolver
beans.Converter
, GenericConverter
, and Formatter
beans.HttpMessageConverters
(covered later in this document).MessageCodesResolver
(covered later in this document).index.html
support.Favicon
support (covered later in this document).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
.
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 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.
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
or JsonDeserializer
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.
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
).
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.
Tip | |
---|---|
Do not use the |
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.
Note | |
---|---|
If you use JBoss, you need to declare the |
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=/**
Note | |
---|---|
Links to resources are rewritten in templates at runtime, thanks to a |
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.
Tip | |
---|---|
This feature has been thoroughly described in a dedicated blog post and in Spring Framework’s reference documentation. |
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.
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.
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 only 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
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.
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:
Tip | |
---|---|
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
.
Tip | |
---|---|
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 |
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.
Tip | |
---|---|
The |
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.
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.ftl +- <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.
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")); } }
Note | |
---|---|
If you register an |
@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.
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. This is necessary as the Servlet specification does not provide an API for registering error pages. Depending on the container that you are deploying your war file to and the technologies that your application uses, some additional configuration may be required.
The error page filter can only forward the request 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
.
If you are using Spring Security and want to access the principal in an error page, you must configure Spring Security’s filter to be invoked on error dispatches.
To do so, set the spring.security.filter.dispatcher-types
property to async, error, forward, request
.
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.
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 public class MyConfiguration { @Bean public WebMvcConfigurer corsConfigurer() { return new WebMvcConfigurer() { @Override public void addCorsMappings(CorsRegistry registry) { registry.addMapping("/api/**"); } }; } }
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 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.
Tip | |
---|---|
You can define as many |
To get started, add the spring-boot-starter-webflux
module to your application.
Note | |
---|---|
Adding both |
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:
HttpMessageReader
and HttpMessageWriter
instances (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
.
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 public class MyConfiguration { @Bean public CodecCustomizer myCodecCustomizer() { return codecConfigurer -> { // ... } } }
You can also leverage Boot’s custom JSON serializers and deserializers.
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.
Tip | |
---|---|
Spring WebFlux applications do not strictly depend on the Servlet API, so they cannot be deployed as war files and do not use the |
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
.
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.
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>
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 |
---|---|
|
|
|
|
|
|
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); } }
Warning | |
---|---|
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 |
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.
There is a Jersey sample so that you can see how to set things up.
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
.
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.
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.
Spring Boot ships with many auto-configurations that may define Filter beans. Here are a few examples of Filters and their respective order (lower order value means higher precedence):
Servlet Filter | Order |
---|---|
|
|
|
|
|
|
|
|
It is usually safe to leave Filter beans unordered.
If a specific order is required, you should annotate the Filter
with @Order
or make it implement Ordered
.
You cannot configure the order of a Filter
by annotating its bean method with @Order
.
If you cannot change the Filter
class to add @Order
or implement Ordered
, you must define a FilterRegistrationBean
for the Filter
and set the registration bean’s order using the setOrder(int)
method.
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
.
Warning | |
---|---|
Take care when registering |
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
.
When using an embedded container, automatic registration of classes annotated with @WebServlet
, @WebFilter
, and @WebListener
can be enabled by using @ServletComponentScan
.
Tip | |
---|---|
|
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.
Note | |
---|---|
You usually do not need to be aware of these implementation classes.
Most applications are auto-configured, and the appropriate |
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:
server.port
), interface address to bind to server.address
, and so on.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.*
).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.
Tip | |
---|---|
See the |
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); } }
Note | |
---|---|
|
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.
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.
java -jar
, and will also be deployable to any standard container.
JSPs are not supported when using an executable jar.error.jsp
page does not override the default view for error handling.
Custom error pages should be used instead.There is a JSP sample so that you can see how to set things up.
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.
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:
WebClient.Builder
bean auto-configured by Spring BootDevelopers 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.
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
Note | |
---|---|
If you fine-tune your logging configuration, ensure that the |
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:
UserDetailsService
(or ReactiveUserDetailsService
in case of a WebFlux application) bean with in-memory store and a single user with a generated password (see SecurityProperties.User
for the properties of the user).Accept
header in the request) for the entire application (including actuator endpoints if actuator is on the classpath).DefaultAuthenticationEventPublisher
for publishing authentication events.You can provide a different AuthenticationEventPublisher
by adding a bean for it.
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
.
There are several secure applications in the Spring Boot samples to get you started with common use cases.
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.
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(); }
OAuth2 is a widely used authorization framework that is supported by Spring.
If you have spring-security-oauth2-client
on your classpath, you can take advantage of some auto-configuration 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=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=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=http://my-auth-server/oauth/authorize spring.security.oauth2.client.provider.my-oauth-provider.token-uri=http://my-auth-server/oauth/token spring.security.oauth2.client.provider.my-oauth-provider.user-info-uri=http://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=http://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"); } }
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
If you have spring-security-oauth2-resource-server
on your classpath, Spring Boot can set up an OAuth2 Resource Server as long as a JWK Set URI or OIDC Issuer URI is 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/
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.
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.
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.
Note | |
---|---|
Before setting the |
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.
Note | |
---|---|
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.
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.
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.
Tip | |
---|---|
See the “How-to” section for more advanced examples, typically to take full control over the configuration of the DataSource. |
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.
Tip | |
---|---|
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.
Note | |
---|---|
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>
Note | |
---|---|
You need a dependency on |
Tip | |
---|---|
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 |
Production database connections can also be auto-configured by using a pooling DataSource
.
Spring Boot uses the following algorithm for choosing a specific implementation:
DataSource
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
.
Note | |
---|---|
You can bypass that algorithm completely and specify the connection pool to use by setting the |
Tip | |
---|---|
Additional connection pools can always be configured manually.
If you define your own |
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
Note | |
---|---|
You should at least specify the URL by setting the |
Tip | |
---|---|
You often do not need to specify the |
Note | |
---|---|
For a pooling |
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
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
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
Note | |
---|---|
The |
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:
Tip | |
---|---|
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. |
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 }
Tip | |
---|---|
You can customize entity scanning locations by using the |
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.
Tip | |
---|---|
We have barely scratched the surface of Spring Data JPA. For complete details, see the Spring Data JPA reference documentation. |
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
Note | |
---|---|
Hibernate’s own internal property name for this (if you happen to remember it better) is |
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.
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
.
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.
Tip | |
---|---|
For complete details of Spring Data JDBC, please refer to the reference documentation. |
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:
com.h2database:h2
is on the classpath.Tip | |
---|---|
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 |
Note | |
---|---|
The H2 console is only intended for use during development, so you should take care to ensure that |
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.
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>
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; } }
Tip | |
---|---|
The jOOQ manual tends to use a variable named |
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); }
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
.
Note | |
---|---|
Spring Boot can only auto-configure dialects supported by the open source version of 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
Settings
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.
Spring Data provides additional projects that help you access a variety of NoSQL technologies, including:
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 spring.io/projects/spring-data.
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.
Tip | |
---|---|
we also provide a |
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; } // ... }
Tip | |
---|---|
You can also register an arbitrary number of beans that implement |
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.
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”.
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.
Note | |
---|---|
If you use the Mongo 3.0 Java driver, |
Tip | |
---|---|
If |
Tip | |
---|---|
If you do not use Spring Data Mongo, you can inject |
Note | |
---|---|
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. |
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 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); }
Tip | |
---|---|
You can customize document scanning locations by using the |
Tip | |
---|---|
For complete details of Spring Data MongoDB, including its rich object mapping technologies, refer to its reference documentation. |
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.
Note | |
---|---|
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.
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”.
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.
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.
Note | |
---|---|
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.
Note | |
---|---|
You can enable persistence for the embedded mode by providing a path to a database file in your configuration, e.g. |
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 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.
Tip | |
---|---|
For complete details of Spring Data Neo4j, including its object mapping technologies, refer to the reference documentation. |
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.
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 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.
IP: For complete details of Spring Data Solr, refer to the reference documentation.
Elasticsearch is an open source, distributed, RESTful search and analytics engine. Spring Boot offers basic auto-configuration for Elasticsearch.
Spring Boot supports several HTTP clients:
The transport client is still being used by Spring Data Elasticsearch, which you can start using with the spring-boot-starter-data-elasticsearch
“Starter”.
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.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.
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.
To connect to Elasticsearch, you must provide the address of one or more cluster nodes.
The address can be specified by setting the spring.data.elasticsearch.cluster-nodes
property to a comma-separated host:port
list.
With this configuration in place, an ElasticsearchTemplate
or TransportClient
can be injected like any other Spring bean, as shown in the following example:
spring.data.elasticsearch.cluster-nodes=localhost:9300
@Component public class MyBean { private final ElasticsearchTemplate template; public MyBean(ElasticsearchTemplate template) { this.template = template; } // ... }
If you add your own ElasticsearchTemplate
or TransportClient
@Bean
, it replaces the default.
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.
Tip | |
---|---|
For complete details of Spring Data Elasticsearch, refer to the reference documentation. |
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.
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 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
.
Tip | |
---|---|
For complete details of Spring Data Cassandra, refer to the reference documentation. |
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.
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
Tip | |
---|---|
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 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:
CouchbaseTemplate
@Bean
with a name of couchbaseTemplate
.IndexManager
@Bean
with a name of couchbaseIndexManager
.CustomConversions
@Bean
with a name of couchbaseCustomConversions
.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 public class SomeConfiguration { @Bean(BeanNames.COUCHBASE_CUSTOM_CONVERSIONS) public CustomConversions myCustomConversions() { return new CustomConversions(...); } // ... }
Tip | |
---|---|
If you want to fully bypass the auto-configuration for Spring Data Couchbase, provide your own implementation of |
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.
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 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; } // ... }
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
Note | |
---|---|
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: spring.ldap.embedded.base-dn: - dc=spring,dc=io - dc=pivotal,dc=io In properties files, you must include the index as part of the property name: spring.ldap.embedded.base-dn[0]=dc=spring,dc=io spring.ldap.embedded.base-dn[1]=dc=pivotal,dc=io |
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.
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.
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.
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.
Note | |
---|---|
Check the relevant section of the Spring Framework reference for more details. |
In a nutshell, to add caching to an operation of your service add 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.
Caution | |
---|---|
You can also use the standard JSR-107 (JCache) annotations (such as |
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.
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):
Tip | |
---|---|
It is also possible to force a particular cache provider by setting the |
Tip | |
---|---|
Use the |
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); } }; }
Note | |
---|---|
In the preceding example, an auto-configured |
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 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
Note | |
---|---|
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. |
Tip | |
---|---|
Spring Boot has general support for Hazelcast.
If a single |
There are two ways to customize the underlying javax.cache.cacheManager
:
spring.cache.cache-names
property.
If a custom javax.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 the CacheManager
for full customization.Tip | |
---|---|
If a standard |
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
Spring Boot has general support for Hazelcast.
If a HazelcastInstance
has been auto-configured, it is automatically wrapped in a CacheManager
.
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.
Note | |
---|---|
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. |
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 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.
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
Note | |
---|---|
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 |
Tip | |
---|---|
You can take full control of the configuration by adding a |
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):
spring.cache.caffeine.spec
com.github.benmanes.caffeine.cache.CaffeineSpec
bean is definedcom.github.benmanes.caffeine.cache.Caffeine
bean is definedFor 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.
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.
When @EnableCaching
is present in your configuration, a suitable cache configuration is expected as well.
If you need to disable caching altogether in certain environments, force the cache type to none
to use a no-op implementation, as shown in the following example:
spring.cache.type=none
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.
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.
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).
Note | |
---|---|
If you use |
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
Tip | |
---|---|
See |
By default, ActiveMQ creates a destination if it does not yet exist so that destinations are resolved against their provided names.
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.
Note | |
---|---|
If you use |
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.
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
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; } // ... }
Note | |
---|---|
|
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) { // ... } }
Tip | |
---|---|
See the Javadoc of |
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 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) { // ... } }
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 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
Alternatively, you could configure the same connection using the addresses
attributes:
spring.rabbitmq.addresses=amqp://admin:secret@localhost
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.
Tip | |
---|---|
See Understanding AMQP, the protocol used by RabbitMQ for more details. |
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; } // ... }
Note | |
---|---|
|
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.
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) { // ... } }
Tip | |
---|---|
See the Javadoc of |
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.
Tip | |
---|---|
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 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.
Important | |
---|---|
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 |
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
Tip | |
---|---|
To create a topic on startup, add a bean of type |
See KafkaProperties
for more supported options.
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; } // ... }
Note | |
---|---|
If the property |
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 RecordMessageConverter
, ErrorHandler
or AfterRollbackProcessor
bean is defined, it is automatically associated to the default factory.
Tip | |
---|---|
A custom |
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 only 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 Section 35.3.4, “Additional Kafka Properties” for more information.
To use the factory bean, wire StreamsBuilder
into your @Bean
as shown in the following example:
@Configuration @EnableKafkaStreams 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.
The properties supported by auto configuration are shown in Appendix A, 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
Important | |
---|---|
Properties set in this way override any configuration item that Spring Boot explicitly supports. |
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); } }
Tip | |
---|---|
|
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.
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); } }
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.
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.
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) { ... } }
The Spring Framework provides an abstraction for sending email by using the JavaMailSender
interface, and Spring Boot provides auto-configuration for it as well as a starter module.
Tip | |
---|---|
See the reference documentation for a detailed explanation of how you can use |
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.
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.
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.
Note | |
---|---|
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 |
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.
Note | |
---|---|
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 |
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
.
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;
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.
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.xml
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.
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:
com.hazelcast.client.config.ClientConfig
bean.spring.hazelcast.config
property.hazelcast.client.config
system property.hazelcast-client.xml
in the working directory or at the root of the classpath.Note | |
---|---|
Spring Boot also has explicit caching support for Hazelcast.
If caching is enabled, the |
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 the JobBuilder
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
Warning | |
---|---|
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 |
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.*
.
Note | |
---|---|
In particular, an |
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 { ... } }
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.
Tip | |
---|---|
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-size=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.
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.
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:
When building a reactive web application, the following stores can be auto-configured:
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
Tip | |
---|---|
You can disable Spring Session by setting the |
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
.
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.
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, AssertJ, Hamcrest, and a number of other useful libraries.
The spring-boot-starter-test
“Starter” (in the test
scope
) contains the following provided libraries:
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.
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.
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.
Note | |
---|---|
External properties, logging, and other features of Spring Boot are installed in the context by default only if you use |
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.
Tip | |
---|---|
If you are using JUnit 4, don’t forget to also add |
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 web ApplicationContext
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-web ApplicationContext
.
It can be used in conjunction with @AutoConfigureMockMvc
or @AutoConfigureWebTestClient
for mock-based testing of your web application.RANDOM_PORT
: Loads a WebServerApplicationContext
and provides a real web environment.
Embedded servers are started and listen on a random port.DEFINED_PORT
: Loads a WebServerApplicationContext
and provides a real web environment.
Embedded servers are started and listen on a defined port (from your application.properties
) or on the default port of 8080
.NONE
: Loads an ApplicationContext
by using SpringApplication
but does not provide any web environment (mock or otherwise).Note | |
---|---|
If your test is |
Note | |
---|---|
|
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:
@RunWith(SpringRunner.class) @SpringBootTest(properties = "spring.main.web-application-type=reactive") public class MyWebFluxTests { ... }
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.
Note | |
---|---|
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.
Note | |
---|---|
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. |
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:
@RunWith(SpringRunner.class) @SpringBootTest @Import(MyTestsConfiguration.class) public class MyTests { @Test public void exampleTest() { ... } }
Note | |
---|---|
If you directly use |
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.Test; import org.junit.runner.RunWith; 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.context.junit4.SpringRunner; 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; @RunWith(SpringRunner.class) @SpringBootTest @AutoConfigureMockMvc public class MockMvcExampleTests { @Autowired private MockMvc mvc; @Test public void exampleTest() throws Exception { this.mvc.perform(get("/")).andExpect(status().isOk()).andExpect(content().string("Hello World")); } }
Tip | |
---|---|
If you want to focus only on the web layer and not start a complete |
Alternatively, you can configure a WebTestClient
as shown in the following example:
import org.junit.Test; import org.junit.runner.RunWith; 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.context.junit4.SpringRunner; import org.springframework.test.web.reactive.server.WebTestClient; @RunWith(SpringRunner.class) @SpringBootTest @AutoConfigureWebTestClient public class MockWebTestClientExampleTests { @Autowired private WebTestClient webClient; @Test public void exampleTest() { this.webClient.get().uri("/").exchange().expectStatus().isOk().expectBody(String.class) .isEqualTo("Hello World"); } }
Tip | |
---|---|
Testing within a mocked environment is usually faster than running with a full Servlet container. However, since mocking occurs at the Spring MVC layer, code that relies on lower-level Servlet container behavior cannot be directly tested with MockMvc. For example, Spring Boot’s error handling is based on the “error page” support provided by the Servlet container. This means that, whilst you can test your MVC layer throws and handles exceptions as expected, you cannot directly test that a specific custom error page is rendered. If you need to test these lower-level concerns, you can start a fully running server as described in the next section. |
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.Test; import org.junit.runner.RunWith; 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.context.junit4.SpringRunner; import org.springframework.test.web.reactive.server.WebTestClient; @RunWith(SpringRunner.class) @SpringBootTest(webEnvironment = WebEnvironment.RANDOM_PORT) public class RandomPortWebTestClientExampleTests { @Autowired private WebTestClient webClient; @Test public void exampleTest() { this.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.Test; import org.junit.runner.RunWith; 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 org.springframework.test.context.junit4.SpringRunner; import static org.assertj.core.api.Assertions.assertThat; @RunWith(SpringRunner.class) @SpringBootTest(webEnvironment = WebEnvironment.RANDOM_PORT) public class RandomPortTestRestTemplateExampleTests { @Autowired private TestRestTemplate restTemplate; @Test public void exampleTest() { String body = this.restTemplate.getForObject("/", String.class); assertThat(body).isEqualTo("Hello World"); } }
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:
@RunWith(SpringRunner.class) @SpringBootTest(properties = "spring.jmx.enabled=true") @DirtiesContext public class SampleJmxTests { @Autowired private MBeanServer mBeanServer; @Test public void exampleTest() { // ... } }
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.
Note | |
---|---|
If your test uses one of Spring Boot’s test annotations (such as @TestExecutionListeners(MockitoTestExecutionListener.class) |
The following example replaces an existing RemoteService
bean with a mock implementation:
import org.junit.*; import org.junit.runner.*; import org.springframework.beans.factory.annotation.*; import org.springframework.boot.test.context.*; import org.springframework.boot.test.mock.mockito.*; import org.springframework.test.context.junit4.*; import static org.assertj.core.api.Assertions.*; import static org.mockito.BDDMockito.*; @RunWith(SpringRunner.class) @SpringBootTest public class MyTests { @MockBean private RemoteService remoteService; @Autowired private Reverser reverser; @Test public void exampleTest() { // RemoteService has been injected into the reverser bean given(this.remoteService.someCall()).willReturn("mock"); String reverse = reverser.reverseSomeCall(); assertThat(reverse).isEqualTo("kcom"); } }
Note | |
---|---|
|
Additionally, you can use @SpyBean
to wrap any existing bean with a Mockito spy
.
See the Javadoc for full details.
Note | |
---|---|
CGLib proxies, such as those created for scoped beans, declare the proxied methods as |
Note | |
---|---|
While Spring’s test framework caches application contexts between tests and reuses a context for tests sharing the same configuration, the use of |
Tip | |
---|---|
If you are using |
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.
Note | |
---|---|
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 |
Note | |
---|---|
Including multiple “slices” by using several |
Tip | |
---|---|
It is also possible to use the |
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:
ObjectMapper
, any @JsonComponent
beans and any Jackson Module
sGson
Jsonb
Tip | |
---|---|
A list of the auto-configurations that are enabled by |
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.*; import org.junit.runner.*; 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 org.springframework.test.context.junit4.*; import static org.assertj.core.api.Assertions.*; @RunWith(SpringRunner.class) @JsonTest public class MyJsonTests { @Autowired private JacksonTester<VehicleDetails> json; @Test public 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 public 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"); } }
Note | |
---|---|
JSON helper classes can also be used directly in standard unit tests.
To do so, call the |
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)));
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
, WebMvcConfigurer
, and HandlerMethodArgumentResolver
.
Regular @Component
beans are not scanned when using this annotation.
Tip | |
---|---|
A list of the auto-configuration settings that are enabled by |
Tip | |
---|---|
If you need to register extra components, such as the Jackson |
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.
Tip | |
---|---|
You can also auto-configure |
import org.junit.*; import org.junit.runner.*; 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.*; @RunWith(SpringRunner.class) @WebMvcTest(UserVehicleController.class) public class MyControllerTests { @Autowired private MockMvc mvc; @MockBean private UserVehicleService userVehicleService; @Test public 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")); } }
Tip | |
---|---|
If you need to configure elements of the auto-configuration (for example, when servlet filters should be applied) you can use attributes in the |
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.*; import org.junit.runner.*; 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.*; @RunWith(SpringRunner.class) @WebMvcTest(UserVehicleController.class) public class MyHtmlUnitTests { @Autowired private WebClient webClient; @MockBean private UserVehicleService userVehicleService; @Test public 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"); } }
Note | |
---|---|
By default, Spring Boot puts |
Warning | |
---|---|
The |
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 Chapter 81, Testing With Spring Security how-to section.
Tip | |
---|---|
Sometimes writing Spring MVC tests is not enough; Spring Boot can help you run full end-to-end tests with an actual server. |
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
, and WebFluxConfigurer
.
Regular @Component
beans are not scanned when the @WebFluxTest
annotation is used.
Tip | |
---|---|
A list of the auto-configurations that are enabled by |
Tip | |
---|---|
If you need to register extra components, such as Jackson |
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.
Tip | |
---|---|
You can also auto-configure |
import org.junit.Test; import org.junit.runner.RunWith; 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.context.junit4.SpringRunner; import org.springframework.test.web.reactive.server.WebTestClient; @RunWith(SpringRunner.class) @WebFluxTest(UserVehicleController.class) public class MyControllerTests { @Autowired private WebTestClient webClient; @MockBean private UserVehicleService userVehicleService; @Test public 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"); } }
Tip | |
---|---|
This setup is only supported by WebFlux applications as using |
Note | |
---|---|
|
Note | |
---|---|
|
Tip | |
---|---|
Sometimes writing Spring WebFlux tests is not enough; Spring Boot can help you run full end-to-end tests with an actual server. |
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
.
Tip | |
---|---|
A list of the auto-configuration settings that are enabled by |
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.Test; import org.junit.runner.RunWith; import org.springframework.boot.test.autoconfigure.orm.jpa.DataJpaTest; import org.springframework.test.context.junit4.SpringRunner; import org.springframework.transaction.annotation.Propagation; import org.springframework.transaction.annotation.Transactional; @RunWith(SpringRunner.class) @DataJpaTest @Transactional(propagation = Propagation.NOT_SUPPORTED) public 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.*; import org.junit.runner.*; import org.springframework.boot.test.autoconfigure.orm.jpa.*; import static org.assertj.core.api.Assertions.*; @RunWith(SpringRunner.class) @DataJpaTest public class ExampleRepositoryTests { @Autowired private TestEntityManager entityManager; @Autowired private UserRepository repository; @Test public 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:
@RunWith(SpringRunner.class) @DataJpaTest @AutoConfigureTestDatabase(replace=Replace.NONE) public class ExampleRepositoryTests { // ... }
@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
.
Tip | |
---|---|
A list of the auto-configurations that are enabled by |
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.Test; import org.junit.runner.RunWith; import org.springframework.boot.test.autoconfigure.jdbc.JdbcTest; import org.springframework.test.context.junit4.SpringRunner; import org.springframework.transaction.annotation.Propagation; import org.springframework.transaction.annotation.Transactional; @RunWith(SpringRunner.class) @JdbcTest @Transactional(propagation = Propagation.NOT_SUPPORTED) public 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 "Section 47.3.12, “Auto-configured Data JPA 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
.
Tip | |
---|---|
A list of the auto-configurations that are enabled by |
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 "Section 47.3.12, “Auto-configured Data JPA 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 "Section 32.6, “Using jOOQ”", earlier in this chapter.)
Regular @Component
beans are not loaded into the ApplicationContext
.
Tip | |
---|---|
A list of the auto-configurations that are enabled by |
@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.Test; import org.junit.runner.RunWith; import org.springframework.boot.test.autoconfigure.jooq.JooqTest; import org.springframework.test.context.junit4.SpringRunner; @RunWith(SpringRunner.class) @JooqTest public 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.
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 "Section 33.2, “MongoDB”", earlier in this chapter.)
Tip | |
---|---|
A list of the auto-configuration settings that are enabled by |
The following class shows the @DataMongoTest
annotation in use:
import org.junit.runner.RunWith; import org.springframework.beans.factory.annotation.Autowired; import org.springframework.boot.test.autoconfigure.data.mongo.DataMongoTest; import org.springframework.data.mongodb.core.MongoTemplate; import org.springframework.test.context.junit4.SpringRunner; @RunWith(SpringRunner.class) @DataMongoTest public 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.junit.runner.RunWith; import org.springframework.boot.autoconfigure.mongo.embedded.EmbeddedMongoAutoConfiguration; import org.springframework.boot.test.autoconfigure.data.mongo.DataMongoTest; import org.springframework.test.context.junit4.SpringRunner; @RunWith(SpringRunner.class) @DataMongoTest(excludeAutoConfiguration = EmbeddedMongoAutoConfiguration.class) public class ExampleDataMongoNonEmbeddedTests { }
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 "Section 33.3, “Neo4j”", earlier in this chapter.)
Tip | |
---|---|
A list of the auto-configuration settings that are enabled by |
The following example shows a typical setup for using Neo4J tests in Spring Boot:
import org.junit.runner.RunWith; import org.springframework.beans.factory.annotation.Autowired; import org.springframework.boot.test.autoconfigure.data.neo4j.DataNeo4jTest; import org.springframework.test.context.junit4.SpringRunner; @RunWith(SpringRunner.class) @DataNeo4jTest public 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.junit.Test; import org.junit.runner.RunWith; import org.springframework.boot.test.autoconfigure.data.neo4j.DataNeo4jTest; import org.springframework.test.context.junit4.SpringRunner; import org.springframework.transaction.annotation.Propagation; import org.springframework.transaction.annotation.Transactional; @RunWith(SpringRunner.class) @DataNeo4jTest @Transactional(propagation = Propagation.NOT_SUPPORTED) public class ExampleNonTransactionalTests { }
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 "Section 33.1, “Redis”", earlier in this chapter.)
Tip | |
---|---|
A list of the auto-configuration settings that are enabled by |
The following example shows the @DataRedisTest
annotation in use:
import org.junit.runner.RunWith; import org.springframework.beans.factory.annotation.Autowired; import org.springframework.boot.test.autoconfigure.data.redis.DataRedisTest; import org.springframework.test.context.junit4.SpringRunner; @RunWith(SpringRunner.class) @DataRedisTest public class ExampleDataRedisTests { @Autowired private YourRepository repository; // }
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 "Section 33.8, “LDAP”", earlier in this chapter.)
Tip | |
---|---|
A list of the auto-configuration settings that are enabled by |
The following example shows the @DataLdapTest
annotation in use:
import org.junit.runner.RunWith; import org.springframework.beans.factory.annotation.Autowired; import org.springframework.boot.test.autoconfigure.data.ldap.DataLdapTest; import org.springframework.ldap.core.LdapTemplate; import org.springframework.test.context.junit4.SpringRunner; @RunWith(SpringRunner.class) @DataLdapTest public 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.junit.runner.RunWith; import org.springframework.boot.autoconfigure.ldap.embedded.EmbeddedLdapAutoConfiguration; import org.springframework.boot.test.autoconfigure.data.ldap.DataLdapTest; import org.springframework.test.context.junit4.SpringRunner; @RunWith(SpringRunner.class) @DataLdapTest(excludeAutoConfiguration = EmbeddedLdapAutoConfiguration.class) public class ExampleDataLdapNonEmbeddedTests { }
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
.
Tip | |
---|---|
A list of the auto-configuration settings that are enabled by |
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:
@RunWith(SpringRunner.class) @RestClientTest(RemoteVehicleDetailsService.class) public class ExampleRestClientTest { @Autowired private RemoteVehicleDetailsService service; @Autowired private MockRestServiceServer server; @Test public 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"); } }
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 rule 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.
@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.Test; import org.junit.runner.RunWith; 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.context.junit4.SpringRunner; 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.*; @RunWith(SpringRunner.class) @WebMvcTest(UserController.class) @AutoConfigureRestDocs public class UserDocumentationTests { @Autowired private MockMvc mvc; @Test public 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}"); } }
@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.junit.runner.RunWith; 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.context.junit4.SpringRunner; import org.springframework.test.web.reactive.server.WebTestClient; import static org.springframework.restdocs.webtestclient.WebTestClientRestDocumentation.document; @RunWith(SpringRunner.class) @WebFluxTest @AutoConfigureRestDocs public 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"); } }
@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.Test; import org.junit.runner.RunWith; 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 org.springframework.test.context.junit4.SpringRunner; import static io.restassured.RestAssured.given; import static org.hamcrest.CoreMatchers.is; import static org.springframework.restdocs.restassured3.RestAssuredRestDocumentation.document; @RunWith(SpringRunner.class) @SpringBootTest(webEnvironment = WebEnvironment.RANDOM_PORT) @AutoConfigureRestDocs public class UserDocumentationTests { @LocalServerPort private int port; @Autowired private RequestSpecification documentationSpec; @Test public void listUsers() { given(this.documentationSpec).filter(document("list-users")).when().port(this.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()); } }
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:
@RunWith(SpringRunner.class) @JdbcTest @ImportAutoConfiguration(IntegrationAutoConfiguration.class) public class ExampleJdbcTests { }
Note | |
---|---|
Make sure to not use the regular |
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 @EnableBatchProcessing public class BatchConfiguration { ... }
Note | |
---|---|
Depending on the complexity of your application, you may either have a single |
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 extends 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.
Tip | |
---|---|
If this is not an option for you, you can create a |
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.
A few test utility classes that are generally useful when testing your application are packaged as part of spring-boot
.
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)
Note | |
---|---|
Using |
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
is a JUnit Rule
that you can use to capture System.out
and System.err
output.
You can declare the capture as a @Rule
and then use toString()
for assertions, as follows:
public class OutputCaptureTests { @Rule public final OutputCapture capture = new OutputCapture(); @Test public void testName() { System.out.println("Hello World!"); assertThat(this.capture.toString()).contains("World"); } }
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.
Tip | |
---|---|
Spring Framework 5.0 provides a new |
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:
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:
@RunWith(SpringRunner.class) @SpringBootTest(webEnvironment = WebEnvironment.RANDOM_PORT) public class SampleWebClientTests { @Autowired private TestRestTemplate template; @Test public void testRequest() { HttpHeaders headers = this.template.getForEntity("/example", String.class).getHeaders(); assertThat(headers.getLocation()).hasHost("other.example.com"); } @TestConfiguration static class Config { @Bean public RestTemplateBuilder restTemplateBuilder() { return new RestTemplateBuilder().setConnectTimeout(Duration.ofSeconds(1)) .setReadTimeout(Duration.ofSeconds(1)); } } }
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>
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
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(); }
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.
Tip | |
---|---|
A demo project is available to showcase how you can create a starter step-by-step. |
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).
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
Note | |
---|---|
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.
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:
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 // Some conditions public class MyAutoConfiguration { // Auto-configured beans @Configuration @ConditionalOnClass(EmbeddedAcmeService.class) static class EmbeddedConfiguration { @Bean @ConditionalOnMissingBean public EmbeddedAcmeService embeddedAcmeService() { ... } } }
Tip | |
---|---|
If you use |
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 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
.
Tip | |
---|---|
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 |
Note | |
---|---|
|
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.
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
.
The @ConditionalOnWebApplication
and @ConditionalOnNotWebApplication
annotations let configuration be included depending on whether the application is a “web application”.
A servlet-based web application is any application that uses a Spring WebApplicationContext
, defines a session
scope, or has a ConfigurableWebEnvironment
.
A reactive web application is any application that uses a ReactiveWebApplicationContext
, or has a ConfigurableReactiveWebEnvironment
.
The @ConditionalOnExpression
annotation lets configuration be included based on the result of a SpEL expression.
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));
Tip | |
---|---|
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 public void defaultServiceBacksOff() { this.contextRunner.withUserConfiguration(UserConfiguration.class).run((context) -> { assertThat(context).hasSingleBean(UserService.class); assertThat(context.getBean(UserService.class)) .isSameAs(context.getBean(UserConfiguration.class).myUserService()); }); } @Configuration static class UserConfiguration { @Bean public UserService myUserService() { return new UserService("mine"); } }
It is also possible to easily customize the Environment
, as shown in the following example:
@Test public 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... }); }
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.
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 public void serviceIsIgnoredIfLibraryIsNotPresent() { this.contextRunner.withClassLoader(new FilteredClassLoader(UserService.class)) .run((context) -> assertThat(context).doesNotHaveBean("userService")); }
A typical Spring Boot starter contains code to auto-configure and customize the infrastructure of a given technology, let’s call that "acme". To make it easily extensible, a number of configuration keys in a dedicated namespace can be exposed to the environment. Finally, a single "starter" dependency is provided to help users get started as easily as possible.
Concretely, a custom starter can contain the following:
autoconfigure
module that contains the auto-configuration code for "acme".starter
module that provides a dependency to the autoconfigure
module as well as "acme" and any additional dependencies that are typically useful.
In a nutshell, adding the starter should provide everything needed to start using that library.This separation in two modules is in no way necessary.
If "acme" has several flavours, options or optional features, then it is better to separate the auto-configuration as you can clearly express the fact some features are optional.
Besides, you have the ability to craft a starter that provides an opinion about those optional dependencies.
At the same time, others can rely only on the autoconfigure
module and craft their own starter with different opinions.
If the auto-configuration is relatively straightforward and does not have optional feature, merging the two modules in the starter is definitely an option.
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
and the starter acme-spring-boot-starter
.
If you only have one module that combines the two, name it acme-spring-boot-starter
.
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 }
Note | |
---|---|
You should only use plain text with |
Here are some rules we follow internally to make sure descriptions are consistent:
boolean
types, start the description with "Whether" or "Enable".java.time.Duration
rather than long
and describe the default unit if it differs from milliseconds, e.g. "If a duration suffix is not specified, seconds will be used".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.
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.
Tip | |
---|---|
You should mark the dependencies to the library as optional so that you can include the |
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"
}
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.
Note | |
---|---|
Either way, your starter must reference the core Spring Boot starter ( |
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.
Spring Boot supports Kotlin 1.2.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.
Tip | |
---|---|
These dependencies and plugins are provided by default if one bootstraps a Kotlin project on start.spring.io. |
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).
Warning | |
---|---|
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. |
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) }
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.
In order to avoid mixing different version of Kotlin dependencies on the classpath, dependency management of the following Kotlin dependencies is provided:
kotlin-reflect
kotlin-runtime
kotlin-stdlib
kotlin-stdlib-jdk7
kotlin-stdlib-jdk8
kotlin-stdlib-jre7
kotlin-stdlib-jre8
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.
@ConfigurationProperties
currently only works with lateinit
or nullable var
properties (the former is recommended), since immutable classes initialized by constructors are not yet supported.
@ConfigurationProperties("example.kotlin") class KotlinExampleProperties { lateinit var name: String lateinit var description: String val myService = MyService() class MyService { lateinit var apiToken: String lateinit var uri: URI } }
Tip | |
---|---|
To generate your own metadata using the annotation processor, |
While it is possible to use JUnit 4 (the default provided by spring-boot-starter-test
) 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 @BeforeAll
and @AfterAll
annotations on non-static methods, which is a good fit for Kotlin.
To use JUnit 5, exclude junit:junit
dependency from spring-boot-starter-test
, add JUnit 5 dependencies, and configure the Maven or Gradle plugin accordingly.
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.
spring
and kotlin
tagsIf 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.
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.
The spring-boot-actuator
module provides all of Spring Boot’s production-ready features.
The recommended way to enable the features is to add a dependency on 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")
}
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).
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
Note | |
---|---|
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 |
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
Note | |
---|---|
management: endpoints: web: exposure: include: "*" |
Note | |
---|---|
If your application is exposed publicly, we strongly recommend that you also secure your endpoints. |
Tip | |
---|---|
If you want to implement your own strategy for when endpoints are exposed, you can register an |
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 public class ActuatorSecurity extends WebSecurityConfigurerAdapter { @Override protected void configure(HttpSecurity http) throws Exception { http.requestMatcher(EndpointRequest.toAnyEndpoint()).authorizeRequests() .anyRequest().hasRole("ENDPOINT_ADMIN") .and() .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:
application.properties.
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 public class ActuatorSecurity extends WebSecurityConfigurerAdapter { @Override protected void configure(HttpSecurity http) throws Exception { http.requestMatcher(EndpointRequest.toAnyEndpoint()).authorizeRequests() .anyRequest().permitAll(); } }