Spring Boot Reference Guide

Authors

Phillip Webb, Dave Syer, Josh Long, Stéphane Nicoll, Rob Winch, Andy Wilkinson, Marcel Overdijk, Christian Dupuis, Sébastien Deleuze

1.3.0.BUILD-SNAPSHOT

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.


Table of Contents

I. Spring Boot Documentation
1. About the documentation
2. Getting help
3. First steps
4. Working with Spring Boot
5. Learning about Spring Boot features
6. Moving to production
7. Advanced topics
II. Getting started
8. Introducing Spring Boot
9. System Requirements
9.1. Servlet containers
10. Installing Spring Boot
10.1. Installation instructions for the Java developer
10.1.1. Maven installation
10.1.2. Gradle installation
10.2. Installing the Spring Boot CLI
10.2.1. Manual installation
10.2.2. Installation with GVM
10.2.3. OSX Homebrew installation
10.2.4. MacPorts installation
10.2.5. Command-line completion
10.2.6. Quick start Spring CLI example
10.3. Upgrading from an earlier version of Spring Boot
11. Developing your first Spring Boot application
11.1. Creating the POM
11.2. Adding classpath dependencies
11.3. Writing the code
11.3.1. The @RestController and @RequestMapping annotations
11.3.2. The @EnableAutoConfiguration annotation
11.3.3. The “main” method
11.4. Running the example
11.5. Creating an executable jar
12. What to read next
III. Using Spring Boot
13. Build systems
13.1. Maven
13.1.1. Inheriting the starter parent
13.1.2. Using Spring Boot without the parent POM
13.1.3. Changing the Java version
13.1.4. Using the Spring Boot Maven plugin
13.2. Gradle
13.3. Ant
13.4. Starter POMs
14. Structuring your code
14.1. Using the “default” package
14.2. Locating the main application class
15. Configuration classes
15.1. Importing additional configuration classes
15.2. Importing XML configuration
16. Auto-configuration
16.1. Gradually replacing auto-configuration
16.2. Disabling specific auto-configuration
17. Spring Beans and dependency injection
18. Using the @SpringBootApplication annotation
19. Running your application
19.1. Running from an IDE
19.2. Running as a packaged application
19.3. Using the Maven plugin
19.4. Using the Gradle plugin
19.5. Hot swapping
20. Developer tools
20.1. Property defaults
20.2. Automatic restart
20.2.1. Excluding resources
20.2.2. Disabling restart
20.2.3. Using a trigger file
20.3. LiveReload
20.4. Global settings
20.5. Remote applications
20.5.1. Running the remote client application
20.5.2. Remote update
20.5.3. Remote debug tunnel
21. Packaging your application for production
22. What to read next
IV. Spring Boot features
23. SpringApplication
23.1. Customizing the Banner
23.2. Customizing SpringApplication
23.3. Fluent builder API
23.4. Application events and listeners
23.5. Web environment
23.6. Using the CommandLineRunner
23.7. Application exit
23.8. Admin features
24. Externalized Configuration
24.1. Configuring random values
24.2. Accessing command line properties
24.3. Application property files
24.4. Profile-specific properties
24.5. Placeholders in properties
24.6. Using YAML instead of Properties
24.6.1. Loading YAML
24.6.2. Exposing YAML as properties in the Spring Environment
24.6.3. Multi-profile YAML documents
24.6.4. YAML shortcomings
24.7. Typesafe Configuration Properties
24.7.1. Third-party configuration
24.7.2. Relaxed binding
24.7.3. @ConfigurationProperties Validation
25. Profiles
25.1. Adding active profiles
25.2. Programmatically setting profiles
25.3. Profile specific configuration files
26. Logging
26.1. Log format
26.2. Console output
26.3. File output
26.4. Log Levels
26.5. Custom log configuration
26.6. Logback extensions
26.6.1. Profile specific configuration
26.6.2. Environment properties
27. Developing web applications
27.1. The ‘Spring Web MVC framework’
27.1.1. Spring MVC auto-configuration
27.1.2. HttpMessageConverters
27.1.3. MessageCodesResolver
27.1.4. Static Content
27.1.5. Template engines
27.1.6. Error Handling
Error Handling on WebSphere Application Server
27.1.7. Spring HATEOAS
27.2. JAX-RS and Jersey
27.3. Embedded servlet container support
27.3.1. Servlets and Filters
27.3.2. The EmbeddedWebApplicationContext
27.3.3. Customizing embedded servlet containers
Programmatic customization
Customizing ConfigurableEmbeddedServletContainer directly
27.3.4. JSP limitations
28. Security
28.1. OAuth2
28.1.1. Authorization Server
28.1.2. Resource Server
28.2. Token Type in User Info
28.3. Customizing the User Info RestTemplate
28.3.1. Client
28.3.2. Single Sign On
28.4. Actuator Security
29. Working with SQL databases
29.1. Configure a DataSource
29.1.1. Embedded Database Support
29.1.2. Connection to a production database
29.1.3. Connection to a JNDI DataSource
29.2. Using JdbcTemplate
29.3. JPA and ‘Spring Data’
29.3.1. Entity Classes
29.3.2. Spring Data JPA Repositories
29.3.3. Creating and dropping JPA databases
30. Using jOOQ
30.1. Code Generation
30.2. Using DSLContext
30.3. Customizing jOOQ
31. Working with NoSQL technologies
31.1. Redis
31.1.1. Connecting to Redis
31.2. MongoDB
31.2.1. Connecting to a MongoDB database
31.2.2. MongoTemplate
31.2.3. Spring Data MongoDB repositories
31.3. Gemfire
31.4. Solr
31.4.1. Connecting to Solr
31.4.2. Spring Data Solr repositories
31.5. Elasticsearch
31.5.1. Connecting to Elasticsearch
31.5.2. Spring Data Elasticsearch repositories
32. Caching
32.1. Supported cache providers
32.1.1. Generic
32.1.2. EhCache 2.x
32.1.3. Hazelcast
32.1.4. Infinispan
32.1.5. JCache
32.1.6. Redis
32.1.7. Guava
32.1.8. Simple
33. Messaging
33.1. JMS
33.1.1. ActiveMQ support
33.1.2. Artemis support
33.1.3. HornetQ support
33.1.4. Using a JNDI ConnectionFactory
33.1.5. Sending a message
33.1.6. Receiving a message
34. Sending email
35. Distributed Transactions with JTA
35.1. Using an Atomikos transaction manager
35.2. Using a Bitronix transaction manager
35.3. Using a Java EE managed transaction manager
35.4. Mixing XA and non-XA JMS connections
35.5. Supporting an alternative embedded transaction manager
36. Spring Integration
37. Spring Session
38. Monitoring and management over JMX
39. Testing
39.1. Test scope dependencies
39.2. Testing Spring applications
39.3. Testing Spring Boot applications
39.3.1. Using Spock to test Spring Boot applications
39.4. Test utilities
39.4.1. ConfigFileApplicationContextInitializer
39.4.2. EnvironmentTestUtils
39.4.3. OutputCapture
39.4.4. TestRestTemplate
40. Developing auto-configuration and using conditions
40.1. Understanding auto-configured beans
40.2. Locating auto-configuration candidates
40.3. Condition annotations
40.3.1. Class conditions
40.3.2. Bean conditions
40.3.3. Property conditions
40.3.4. Resource conditions
40.3.5. Web application conditions
40.3.6. SpEL expression conditions
41. WebSockets
42. What to read next
V. Spring Boot Actuator: Production-ready features
43. Enabling production-ready features
44. Endpoints
44.1. Customizing endpoints
44.2. Hypermedia for MVC Endpoints
44.3. Adding Custom Endpoints
44.4. Health information
44.5. Security with HealthIndicators
44.5.1. Auto-configured HealthIndicators
44.5.2. Writing custom HealthIndicators
44.6. Custom application info information
44.6.1. Automatically expand info properties at build time
Automatic property expansion using Maven
Automatic property expansion using Gradle
44.6.2. Git commit information
45. Monitoring and management over HTTP
45.1. Securing sensitive endpoints
45.2. Customizing the management server context path
45.3. Customizing the management server port
45.4. Customizing the management server address
45.5. Disabling HTTP endpoints
45.6. HTTP health endpoint access restrictions
46. Monitoring and management over JMX
46.1. Customizing MBean names
46.2. Disabling JMX endpoints
46.3. Using Jolokia for JMX over HTTP
46.3.1. Customizing Jolokia
46.3.2. Disabling Jolokia
47. Monitoring and management using a remote shell
47.1. Connecting to the remote shell
47.1.1. Remote shell credentials
47.2. Extending the remote shell
47.2.1. Remote shell commands
47.2.2. Remote shell plugins
48. Metrics
48.1. System metrics
48.2. DataSource metrics
48.3. Cache metrics
48.4. Tomcat session metrics
48.5. Recording your own metrics
48.6. Adding your own public metrics
48.7. Special features with Java 8
48.8. Metric writers, exporters and aggregation
48.8.1. Example: Export to Redis
48.8.2. Example: Export to Open TSDB
48.8.3. Example: Export to Statsd
48.8.4. Example: Export to JMX
48.9. Aggregating metrics from multiple sources
48.10. Dropwizard Metrics
48.11. Message channel integration
49. Auditing
50. Tracing
50.1. Custom tracing
51. Process monitoring
51.1. Extend configuration
51.2. Programmatically
52. What to read next
53. Deploying Spring Boot applications
54. Deploying to the cloud
54.1. Cloud Foundry
54.1.1. Binding to services
54.2. Heroku
54.3. Openshift
54.4. Google App Engine
55. Installing Spring Boot applications
55.1. Unix/Linux services
55.1.1. Installation as a init.d service (System V)
55.1.2. Installation as a systemd service
55.1.3. Customizing the startup script
56. What to read next
VI. Spring Boot CLI
57. Installing the CLI
58. Using the CLI
58.1. Running applications using the CLI
58.1.1. Deduced “grab” dependencies
58.1.2. Deduced “grab” coordinates
58.1.3. Default import statements
58.1.4. Automatic main method
58.1.5. Custom dependency management
58.2. Testing your code
58.3. Applications with multiple source files
58.4. Packaging your application
58.5. Initialize a new project
58.6. Using the embedded shell
58.7. Adding extensions to the CLI
59. Developing application with the Groovy beans DSL
60. What to read next
VII. Build tool plugins
61. Spring Boot Maven plugin
61.1. Including the plugin
61.2. Packaging executable jar and war files
62. Spring Boot Gradle plugin
62.1. Including the plugin
62.2. Dependency management
62.3. Packaging executable jar and war files
62.4. Running a project in-place
62.5. Spring Boot plugin configuration
62.6. Repackage configuration
62.7. Repackage with custom Gradle configuration
62.7.1. Configuration options
62.8. Understanding how the Gradle plugin works
62.9. Publishing artifacts to a Maven repository using Gradle
62.9.1. Configuring Gradle to produce a pom that inherits dependency management
62.9.2. Configuring Gradle to produce a pom that imports dependency management
63. Spring Boot AntLib module
63.1. Spring Boot Ant tasks
63.1.1. spring-boot:exejar
Examples
63.2. spring-boot:findmainclass
63.2.1. Examples
64. Supporting other build systems
64.1. Repackaging archives
64.2. Nested libraries
64.3. Finding a main class
64.4. Example repackage implementation
65. What to read next
VIII. ‘How-to’ guides
66. Spring Boot application
66.1. Troubleshoot auto-configuration
66.2. Customize the Environment or ApplicationContext before it starts
66.3. Build an ApplicationContext hierarchy (adding a parent or root context)
66.4. Create a non-web application
67. Properties & configuration
67.1. Externalize the configuration of SpringApplication
67.2. Change the location of external properties of an application
67.3. Use ‘short’ command line arguments
67.4. Use YAML for external properties
67.5. Set the active Spring profiles
67.6. Change configuration depending on the environment
67.7. Discover built-in options for external properties
68. Embedded servlet containers
68.1. Add a Servlet, Filter or ServletContextListener to an application
68.2. Disable registration of a Servlet or Filter
68.3. Change the HTTP port
68.4. Use a random unassigned HTTP port
68.5. Discover the HTTP port at runtime
68.6. Configure SSL
68.7. Configure Tomcat
68.8. Enable Multiple Connectors with Tomcat
68.9. Use Tomcat behind a front-end proxy server
68.10. Use Jetty instead of Tomcat
68.11. Configure Jetty
68.12. Use Undertow instead of Tomcat
68.13. Configure Undertow
68.14. Enable Multiple Listeners with Undertow
68.15. Use Tomcat 7
68.15.1. Use Tomcat 7 with Maven
68.15.2. Use Tomcat 7 with Gradle
68.16. Use Jetty 8
68.16.1. Use Jetty 8 with Maven
68.16.2. Use Jetty 8 with Gradle
68.17. Create WebSocket endpoints using @ServerEndpoint
68.18. Enable HTTP response compression
69. Spring MVC
69.1. Write a JSON REST service
69.2. Write an XML REST service
69.3. Customize the Jackson ObjectMapper
69.4. Customize the @ResponseBody rendering
69.5. Handling Multipart File Uploads
69.6. Switch off the Spring MVC DispatcherServlet
69.7. Switch off the Default MVC configuration
69.8. Customize ViewResolvers
70. Logging
70.1. Configure Logback for logging
70.2. Configure Log4j for logging
70.2.1. Use YAML or JSON to configure Log4j 2
71. Data Access
71.1. Configure a DataSource
71.2. Configure Two DataSources
71.3. Use Spring Data repositories
71.4. Separate @Entity definitions from Spring configuration
71.5. Configure JPA properties
71.6. Use a custom EntityManagerFactory
71.7. Use Two EntityManagers
71.8. Use a traditional persistence.xml
71.9. Use Spring Data JPA and Mongo repositories
71.10. Expose Spring Data repositories as REST endpoint
72. Database initialization
72.1. Initialize a database using JPA
72.2. Initialize a database using Hibernate
72.3. Initialize a database using Spring JDBC
72.4. Initialize a Spring Batch database
72.5. Use a higher level database migration tool
72.5.1. Execute Flyway database migrations on startup
72.5.2. Execute Liquibase database migrations on startup
73. Batch applications
73.1. Execute Spring Batch jobs on startup
74. Actuator
74.1. Change the HTTP port or address of the actuator endpoints
74.2. Customize the ‘whitelabel’ error page
75. Security
75.1. Switch off the Spring Boot security configuration
75.2. Change the AuthenticationManager and add user accounts
75.3. Enable HTTPS when running behind a proxy server
76. Hot swapping
76.1. Reload static content
76.2. Reload templates without restarting the container
76.2.1. Thymeleaf templates
76.2.2. FreeMarker templates
76.2.3. Groovy templates
76.2.4. Velocity templates
76.3. Fast application restarts
76.4. Reload Java classes without restarting the container
76.4.1. Configuring Spring Loaded for use with Maven
76.4.2. Configuring Spring Loaded for use with Gradle and IntelliJ IDEA
77. Build
77.1. Customize dependency versions with Maven
77.2. Create an executable JAR with Maven
77.3. Create an additional executable JAR
77.4. Extract specific libraries when an executable jar runs
77.5. Create a non-executable JAR with exclusions
77.6. Remote debug a Spring Boot application started with Maven
77.7. Remote debug a Spring Boot application started with Gradle
77.8. Build an executable archive from Ant without using spring-boot-antlib
77.9. How to use Java 6
77.9.1. Embedded servlet container compatibility
77.9.2. JTA API compatibility
78. Traditional deployment
78.1. Create a deployable war file
78.2. Create a deployable war file for older servlet containers
78.3. Convert an existing application to Spring Boot
78.4. Deploying a WAR to Weblogic
78.5. Deploying a WAR in an Old (Servlet 2.5) Container
IX. Appendices
A. Common application properties
B. Configuration meta-data
B.1. Meta-data format
B.1.1. Group Attributes
B.1.2. Property Attributes
B.1.3. Hint Attributes
B.1.4. Repeated meta-data items
B.2. Providing manual hints
B.2.1. Value hints
B.2.2. Provider hints
Any
Class reference
Enum
Logger name
Spring bean reference
B.3. Generating your own meta-data using the annotation processor
B.3.1. Nested properties
B.3.2. Adding additional meta-data
C. Auto-configuration classes
C.1. From the “spring-boot-autoconfigure” module
C.2. From the “spring-boot-actuator” module
D. The executable jar format
D.1. Nested JARs
D.1.1. The executable jar file structure
D.1.2. The executable war file structure
D.2. Spring Boot’s “JarFile” class
D.2.1. Compatibility with the standard Java “JarFile”
D.3. Launching executable jars
D.3.1. Launcher manifest
D.3.2. Exploded archives
D.4. PropertiesLauncher Features
D.5. Executable jar restrictions
D.5.1. Zip entry compression
D.5.2. System ClassLoader
D.6. Alternative single jar solutions
E. Dependency versions

Part I. Spring Boot Documentation

This section provides a brief overview of Spring Boot reference documentation. Think of it as map for the rest of the document. You can read this reference guide in a linear fashion, or you can skip sections if something doesn’t interest you.

1. About the documentation

The Spring Boot reference guide is available as html, pdf and epub documents. 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.

2. Getting help

Having trouble with Spring Boot, We’d like to help!

[Note]Note

All of Spring Boot is open source, including the documentation! If you find problems with the docs; or if you just want to improve them, please get involved.

3. First steps

If you’re just getting started with Spring Boot, or 'Spring' in general, this is the place to start!

4. Working with Spring Boot

Ready to actually start using Spring Boot? We’ve got you covered.

5. Learning about Spring Boot features

Need more details about Spring Boot’s core features? This is for you!

6. Moving to production

When you’re ready to push your Spring Boot application to production, we’ve got some tricks that you might like!

7. Advanced topics

Lastly, we have a few topics for the more advanced user.

Part II. Getting started

If you’re just getting started with Spring Boot, or 'Spring' in general, this is the section for you! Here we answer the basic “what?”, “how?” and “why?” questions. You’ll find a gentle introduction to Spring Boot along with installation instructions. We’ll then build our first Spring Boot application, discussing some core principles as we go.

8. Introducing Spring Boot

Spring Boot makes it easy to create stand-alone, production-grade Spring based Applications that you can “just run”. We take an opinionated view of the Spring platform and third-party libraries so 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 using java -jar or more traditional war deployments. We also provide a command line tool that runs “spring scripts”.

Our primary goals are:

  • Provide a radically faster and widely accessible getting started experience for all Spring development.
  • Be opinionated out of the box, but get out of the way quickly as requirements start to diverge from the defaults.
  • Provide a range of non-functional features that are common to large classes of projects (e.g. embedded servers, security, metrics, health checks, externalized configuration).
  • Absolutely no code generation and no requirement for XML configuration.

9. System Requirements

By default, Spring Boot 1.3.0.BUILD-SNAPSHOT requires Java 7 and Spring Framework 4.1.5 or above. You can use Spring Boot with Java 6 with some additional configuration. See Section 77.9, “How to use Java 6” for more details. Explicit build support is provided for Maven (3.2+) and Gradle (1.12+).

[Tip]Tip

Although you can use Spring Boot with Java 6 or 7, we generally recommend Java 8 if at all possible.

9.1 Servlet containers

The following embedded servlet containers are supported out of the box:

NameServlet VersionJava Version

Tomcat 8

3.1

Java 7+

Tomcat 7

3.0

Java 6+

Jetty 9

3.1

Java 7+

Jetty 8

3.0

Java 6+

Undertow 1.1

3.1

Java 7+

You can also deploy Spring Boot applications to any Servlet 3.0+ compatible container.

10. Installing Spring Boot

Spring Boot can be used with “classic” Java development tools or installed as a command line tool. Regardless, you will need Java SDK v1.6 or higher. You should check your current Java installation before you begin:

$ java -version

If you are new to Java development, or if you just want to experiment with Spring Boot you might want to try the Spring Boot CLI first, otherwise, read on for “classic” installation instructions.

[Tip]Tip

Although Spring Boot is compatible with Java 1.6, if possible, you should consider using the latest version of Java.

10.1 Installation instructions for the Java developer

You can use Spring Boot in the same way as any standard Java library. Simply 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; and there is nothing special about a Spring Boot application, so you can run and debug as you would any other Java program.

Although you could just copy Spring Boot jars, we generally recommend that you use a build tool that supports dependency management (such as Maven or Gradle).

10.1.1 Maven installation

Spring Boot is compatible with Apache Maven 3.2 or above. If you don’t already have Maven installed you can follow the instructions at maven.apache.org.

[Tip]Tip

On many operating systems Maven can be installed via a package manager. If you’re an OSX Homebrew user try brew install maven. Ubuntu users can run sudo apt-get install maven.

Spring Boot dependencies use the org.springframework.boot groupId. Typically your Maven POM file will inherit from the spring-boot-starter-parent project and declare dependencies to one or more “Starter POMs”. Spring Boot also provides an optional Maven plugin to create executable jars.

Here is 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 http://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>1.3.0.BUILD-SNAPSHOT</version>
    </parent>

    <!-- Add typical dependencies for a web application -->
    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
    </dependencies>

    <!-- Package as an executable jar -->
    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>

    <!-- Add Spring repositories -->
    <!-- (you don't need this if you are using a .RELEASE version) -->
    <repositories>
        <repository>
            <id>spring-snapshots</id>
            <url>http://repo.spring.io/snapshot</url>
            <snapshots><enabled>true</enabled></snapshots>
        </repository>
        <repository>
            <id>spring-milestones</id>
            <url>http://repo.spring.io/milestone</url>
        </repository>
    </repositories>
    <pluginRepositories>
        <pluginRepository>
            <id>spring-snapshots</id>
            <url>http://repo.spring.io/snapshot</url>
        </pluginRepository>
        <pluginRepository>
            <id>spring-milestones</id>
            <url>http://repo.spring.io/milestone</url>
        </pluginRepository>
    </pluginRepositories>
</project>
[Tip]Tip

The spring-boot-starter-parent is a great way to use Spring Boot, but it might not be suitable all of the time. Sometimes you may need to inherit from a different parent POM, or you might just not like our default settings. See Section 13.1.2, “Using Spring Boot without the parent POM” for an alternative solution that uses an import scope.

10.1.2 Gradle installation

Spring Boot is compatible with Gradle 1.12 or above. If you don’t already have Gradle installed you can follow the instructions at www.gradle.org/.

Spring Boot dependencies can be declared using the org.springframework.boot group. Typically your project will declare dependencies to one or more “Starter POMs”. Spring Boot provides a useful Gradle plugin that can be used to simplify dependency declarations and to create executable jars.

Here is a typical build.gradle file:

buildscript {
    repositories {
        jcenter()
        maven { url "http://repo.spring.io/snapshot" }
        maven { url "http://repo.spring.io/milestone" }
    }
    dependencies {
        classpath("org.springframework.boot:spring-boot-gradle-plugin:1.3.0.BUILD-SNAPSHOT")
    }
}

apply plugin: 'java'
apply plugin: 'spring-boot'

jar {
    baseName = 'myproject'
    version =  '0.0.1-SNAPSHOT'
}

repositories {
    jcenter()
    maven { url "http://repo.spring.io/snapshot" }
    maven { url "http://repo.spring.io/milestone" }
}

dependencies {
    compile("org.springframework.boot:spring-boot-starter-web")
    testCompile("org.springframework.boot:spring-boot-starter-test")
}

10.2 Installing the Spring Boot CLI

The Spring Boot CLI is a command line tool that can be used if you want to quickly prototype with Spring. It allows you to run Groovy scripts, which means that you have a familiar Java-like syntax, without so much boilerplate code.

You don’t need to use the CLI to work with Spring Boot but it’s definitely the quickest way to get a Spring application off the ground.

10.2.1 Manual installation

You can download the Spring CLI distribution from the Spring software repository:

Cutting edge snapshot distributions are also available.

Once downloaded, follow the INSTALL.txt instructions from the unpacked archive. In summary: there is a spring script (spring.bat for Windows) in a bin/ directory in the .zip file, or alternatively you can use java -jar with the .jar file (the script helps you to be sure that the classpath is set correctly).

10.2.2 Installation with GVM

GVM (the Groovy Environment Manager) can be used for managing multiple versions of various Groovy and Java binary packages, including Groovy itself and the Spring Boot CLI. Get gvm from gvmtool.net and install Spring Boot with

$ gvm install springboot
$ spring --version
Spring Boot v1.3.0.BUILD-SNAPSHOT

If you are developing features for the CLI and want easy access to the version you just built, follow these extra instructions.

$ gvm install springboot dev /path/to/spring-boot/spring-boot-cli/target/spring-boot-cli-1.3.0.BUILD-SNAPSHOT-bin/spring-1.3.0.BUILD-SNAPSHOT/
$ gvm use springboot dev
$ spring --version
Spring CLI v1.3.0.BUILD-SNAPSHOT

This will install a local instance of spring called the dev instance inside your gvm repository. It points at your target build location, so every time you rebuild Spring Boot, spring will be up-to-date.

You can see it by doing this:

$ gvm ls springboot

================================================================================
Available Springboot Versions
================================================================================
> + dev
* 1.3.0.BUILD-SNAPSHOT

================================================================================
+ - local version
* - installed
> - currently in use
================================================================================

10.2.3 OSX Homebrew installation

If you are on a Mac and using Homebrew, all you need to do to install the Spring Boot CLI is:

$ brew tap pivotal/tap
$ brew install springboot

Homebrew will install spring to /usr/local/bin.

[Note]Note

If you don’t see the formula, your installation of brew might be out-of-date. Just execute brew update and try again.

10.2.4 MacPorts installation

If you are on a Mac and using MacPorts, all you need to do to install the Spring Boot CLI is:

$ sudo port install spring-boot-cli

10.2.5 Command-line completion

Spring Boot CLI ships with scripts that provide command completion for 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. To run the script manually, e.g. if you have installed using GVM

$ . ~/.gvm/springboot/current/shell-completion/bash/spring
$ spring <HIT TAB HERE>
  grab  help  jar  run  test  version
[Note]Note

If you install Spring Boot CLI using Homebrew or MacPorts, the command-line completion scripts are automatically registered with your shell.

10.2.6 Quick start Spring CLI example

Here’s a really simple web application that you can use to test your installation. Create a file called app.groovy:

@RestController
class ThisWillActuallyRun {

    @RequestMapping("/")
    String home() {
        "Hello World!"
    }

}

Then simply run it from a shell:

$ spring run app.groovy
[Note]Note

It will take some time when you first run the application as dependencies are downloaded. Subsequent runs will be much quicker.

Open localhost:8080 in your favorite web browser and you should see the following output:

Hello World!

10.3 Upgrading from an earlier version of Spring Boot

If you are upgrading from an earlier release of Spring Boot check the “release notes” hosted on the project wiki. You’ll find upgrade instructions along with a list of “new and noteworthy” features for each release.

To upgrade an existing CLI installation use the appropriate package manager command (for example brew upgrade) or, if you manually installed the CLI, follow the standard instructions remembering to update your PATH environment variable to remove any older references.

11. Developing your first Spring Boot application

Let’s develop a simple “Hello World!” web application in Java that highlights some of Spring Boot’s key features. We’ll use Maven to build this project since most IDEs support it.

[Tip]Tip

The spring.io web site contains many “Getting Started” guides that use Spring Boot. If you’re looking to solve a specific problem; check there first.

Before we begin, open a terminal to check that you have valid versions of Java and Maven installed.

$ java -version
java version "1.7.0_51"
Java(TM) SE Runtime Environment (build 1.7.0_51-b13)
Java HotSpot(TM) 64-Bit Server VM (build 24.51-b03, mixed mode)
$ mvn -v
Apache Maven 3.2.3 (33f8c3e1027c3ddde99d3cdebad2656a31e8fdf4; 2014-08-11T13:58:10-07:00)
Maven home: /Users/user/tools/apache-maven-3.1.1
Java version: 1.7.0_51, vendor: Oracle Corporation
[Note]Note

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”.

11.1 Creating the POM

We need to start by creating a Maven pom.xml file. The pom.xml is the recipe that will be 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 http://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>1.3.0.BUILD-SNAPSHOT</version>
    </parent>

    <!-- Additional lines to be added here... -->

    <!-- (you don't need this if you are using a .RELEASE version) -->
    <repositories>
        <repository>
            <id>spring-snapshots</id>
            <url>http://repo.spring.io/snapshot</url>
            <snapshots><enabled>true</enabled></snapshots>
        </repository>
        <repository>
            <id>spring-milestones</id>
            <url>http://repo.spring.io/milestone</url>
        </repository>
    </repositories>
    <pluginRepositories>
        <pluginRepository>
            <id>spring-snapshots</id>
            <url>http://repo.spring.io/snapshot</url>
        </pluginRepository>
        <pluginRepository>
            <id>spring-milestones</id>
            <url>http://repo.spring.io/milestone</url>
        </pluginRepository>
    </pluginRepositories>
</project>

This should give you a working build, you can test it out by running mvn package (you can ignore the “jar will be empty - no content was marked for inclusion!” warning for now).

[Note]Note

At this point you could import the project into an IDE (most modern Java IDE’s include built-in support for Maven). For simplicity, we will continue to use a plain text editor for this example.

11.2 Adding classpath dependencies

Spring Boot provides a number of “Starter POMs” that make easy to 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 “Starter POMs” simply provide dependencies that you are likely to need when developing a specific type of application. Since we are developing a web application, we will add a spring-boot-starter-web dependency — but before that, let’s look at what we currently have.

$ 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. Let’s edit our pom.xml and add the spring-boot-starter-web dependency just 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 will see that there are now a number of additional dependencies, including the Tomcat web server and Spring Boot itself.

11.3 Writing the code

To finish our application we need to create a single Java file. Maven will compile sources from src/main/java by default so you need to create that folder structure, then add a file named src/main/java/Example.java:

import org.springframework.boot.*;
import org.springframework.boot.autoconfigure.*;
import org.springframework.stereotype.*;
import org.springframework.web.bind.annotation.*;

@RestController
@EnableAutoConfiguration
public class Example {

    @RequestMapping("/")
    String home() {
        return "Hello World!";
    }

    public static void main(String[] args) throws Exception {
        SpringApplication.run(Example.class, args);
    }

}

Although there isn’t much code here, quite a lot is going on. Let’s step through the important parts.

11.3.1 The @RestController and @RequestMapping annotations

The first annotation on our Example class is @RestController. This is known as a stereotype annotation. It provides hints for people reading the code, and for Spring, that the class plays a specific role. In this case, our class is a web @Controller so Spring will consider it when handling incoming web requests.

The @RequestMapping annotation provides “routing” information. It is telling 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]Tip

The @RestController and @RequestMapping annotations are Spring MVC annotations (they are not specific to Spring Boot). See the MVC section in the Spring Reference Documentation for more details.

11.3.2 The @EnableAutoConfiguration annotation

The second class-level annotation is @EnableAutoConfiguration. This annotation tells Spring Boot to “guess” how you will 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 will assume that you are developing a web application and setup Spring accordingly.

11.3.3 The “main” method

The final part of our application is the main method. This is just a standard method that follows the Java convention for an application entry point. Our main method delegates to Spring Boot’s SpringApplication class by calling run. SpringApplication will bootstrap our application, starting Spring which will in turn start 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.

11.4 Running the example

At this point our application should work. Since we have used the spring-boot-starter-parent POM we have a useful run goal that we can use to start the application. Type mvn spring-boot:run from the root project directory to start the application:

$ mvn spring-boot:run

  .   ____          _            __ _ _
 /\\ / ___'_ __ _ _(_)_ __  __ _ \ \ \ \
( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \
 \\/  ___)| |_)| | | | | || (_| |  ) ) ) )
  '  |____| .__|_| |_|_| |_\__, | / / / /
 =========|_|==============|___/=/_/_/_/
 :: Spring Boot ::  (v1.3.0.BUILD-SNAPSHOT)
....... . . .
....... . . . (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 hit ctrl-c.

11.5 Creating an executable jar

Let’s 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. 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]Note

The spring-boot-starter-parent POM includes <executions> configuration to bind the repackage goal. If you are not using the parent POM you will need to declare this configuration yourself. See the plugin documentation for details.

Save your pom.xml and run mvn package from the command line:

$ 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:1.3.0.BUILD-SNAPSHOT: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:

$ 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:

$ java -jar target/myproject-0.0.1-SNAPSHOT.jar

  .   ____          _            __ _ _
 /\\ / ___'_ __ _ _(_)_ __  __ _ \ \ \ \
( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \
 \\/  ___)| |_)| | | | | || (_| |  ) ) ) )
  '  |____| .__|_| |_|_| |_\__, | / / / /
 =========|_|==============|___/=/_/_/_/
 :: Spring Boot ::  (v1.3.0.BUILD-SNAPSHOT)
....... . . .
....... . . . (log output here)
....... . . .
........ Started Example in 2.536 seconds (JVM running for 2.864)

As before, to gracefully exit the application hit ctrl-c.

12. What to read next

Hopefully this section has provided you with some of the Spring Boot basics, and got you on your way to writing your own applications. If you’re a task-oriented type of developer you might want to jump over to spring.io and check out some of the getting started guides that solve specific “How do I do that with Spring” problems; we also have Spring Boot-specific How-to reference documentation.

Otherwise, the next logical step is to read Part III, “Using Spring Boot”. If you’re really impatient, you could also jump ahead and read about Spring Boot features.

Part III. Using Spring Boot

This section goes into more detail about how you should use Spring Boot. It covers topics such as build systems, auto-configuration and how to run your applications. We also cover some Spring Boot best practices. Although there is nothing particularly special about Spring Boot (it is just another library that you can consume), there are a few recommendations that, when followed, will make your development process just a little easier.

If you’re just starting out with Spring Boot, you should probably read the Getting Started guide before diving into this section.

13. Build systems

It is strongly recommended that you choose a build system that supports dependency management, and one 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 will not be particularly well supported.

13.1 Maven

Maven users can inherit from the spring-boot-starter-parent project to obtain sensible defaults. The parent project provides the following features:

  • Java 1.6 as the default compiler level.
  • UTF-8 source encoding.
  • A Dependency Management section, allowing you to omit <version> tags for common dependencies, inherited from the spring-boot-dependencies POM.
  • Sensible resource filtering.
  • Sensible plugin configuration (exec plugin, surefire, Git commit ID, shade).
  • Sensible resource filtering for application.properties and application.yml

On the last point: since the default config files accept Spring style placeholders (${…​}) the Maven filtering is changed to use @..@ placeholders (you can override that with a Maven property resource.delimiter).

13.1.1 Inheriting the starter parent

To configure your project to inherit from the spring-boot-starter-parent simply set the parent:

<!-- Inherit defaults from Spring Boot -->
<parent>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-parent</artifactId>
    <version>1.3.0.BUILD-SNAPSHOT</version>
</parent>
[Note]Note

You should only need to specify the Spring Boot version number on this dependency. If you import additional starters, you can safely omit the version number.

13.1.2 Using Spring Boot without the parent POM

Not everyone likes inheriting from the spring-boot-starter-parent POM. You may have your own corporate standard parent that you need to use, or you may just prefer to explicitly declare all your Maven configuration.

If you don’t 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:

<dependencyManagement>
     <dependencies>
        <dependency>
            <!-- Import dependency management from Spring Boot -->
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-dependencies</artifactId>
            <version>1.3.0.BUILD-SNAPSHOT</version>
            <type>pom</type>
            <scope>import</scope>
        </dependency>
    </dependencies>
</dependencyManagement>

13.1.3 Changing the Java version

The spring-boot-starter-parent chooses fairly conservative Java compatibility. If you want to follow our recommendation and use a later Java version you can add a java.version property:

<properties>
    <java.version>1.8</java.version>
</properties>

13.1.4 Using the Spring Boot Maven plugin

Spring Boot includes a Maven plugin that can package the project as an executable jar. Add the plugin to your <plugins> section if you want to use it:

<build>
    <plugins>
        <plugin>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-maven-plugin</artifactId>
        </plugin>
    </plugins>
</build>
[Note]Note

If you use the Spring Boot starter parent pom, you only need to add the plugin, there is no need for to configure it unless you want to change the settings defined in the parent.

13.2 Gradle

Gradle users can directly import “starter POMs” in their dependencies section. Unlike Maven, there is no “super parent” to import to share some configuration.

apply plugin: 'java'

repositories {
    maven { url "http://repo.spring.io/snapshot" }
    maven { url "http://repo.spring.io/milestone" }
}

dependencies {
    compile("org.springframework.boot:spring-boot-starter-web:1.3.0.BUILD-SNAPSHOT")
}

The spring-boot-gradle-plugin is also available and provides tasks to create executable jars and run projects from source. It also provides dependency management that, among other capabilities, allows you to omit the version number for any dependencies that are managed by Spring Boot:

buildscript {
    repositories {
        maven { url "http://repo.spring.io/snapshot" }
        maven { url "http://repo.spring.io/milestone" }
    }

    dependencies {
        classpath("org.springframework.boot:spring-boot-gradle-plugin:1.3.0.BUILD-SNAPSHOT")
    }
}

apply plugin: 'java'
apply plugin: 'spring-boot'

repositories {
    maven { url "http://repo.spring.io/snapshot" }
    maven { url "http://repo.spring.io/milestone" }
}

dependencies {
    compile("org.springframework.boot:spring-boot-starter-web")
    testCompile("org.springframework.boot:spring-boot-starter-test")
}

13.3 Ant

It is possible to build a Spring Boot project using Apache Ant+Ivy. The spring-boot-antlib “AntLib” module is also available to help Ant create executable jars.

To declare dependencies a typical ivy.xml file will look something like this:

<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 will look like this:

<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="1.3.0.BUILD-SNAPSHOT" />

    <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]Tip

See the Section 77.8, “Build an executable archive from Ant without using spring-boot-antlib” “How-to” if you don’t want to use the spring-boot-antlib module.

13.4 Starter POMs

Starter POMs 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 technology 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, just include the spring-boot-starter-data-jpa dependency in your project, and you are good to go.

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 13.1. Spring Boot application starters

NameDescription

spring-boot-starter

The core Spring Boot starter, including auto-configuration support, logging and YAML.

spring-boot-starter-actuator

Production ready features to help you monitor and manage your application.

spring-boot-starter-amqp

Support for the “Advanced Message Queuing Protocol” via spring-rabbit.

spring-boot-starter-aop

Support for aspect-oriented programming including spring-aop and AspectJ.

spring-boot-starter-artemis

Support for “Java Message Service API” via Apache Artemis.

spring-boot-starter-batch

Support for “Spring Batch” including HSQLDB database.

spring-boot-starter-cache

Support for Spring’s Cache abstraction.

spring-boot-starter-cloud-connectors

Support for “Spring Cloud Connectors” which simplifies connecting to services in cloud platforms like Cloud Foundry and Heroku.

spring-boot-starter-data-elasticsearch

Support for the Elasticsearch search and analytics engine including spring-data-elasticsearch.

spring-boot-starter-data-gemfire

Support for the GemFire distributed data store including spring-data-gemfire.

spring-boot-starter-data-jpa

Support for the “Java Persistence API” including spring-data-jpa, spring-orm and Hibernate.

spring-boot-starter-data-mongodb

Support for the MongoDB NoSQL Database, including spring-data-mongodb.

spring-boot-starter-data-rest

Support for exposing Spring Data repositories over REST via spring-data-rest-webmvc.

spring-boot-starter-data-solr

Support for the Apache Solr search platform, including spring-data-solr.

spring-boot-starter-freemarker

Support for the FreeMarker templating engine.

spring-boot-starter-groovy-templates

Support for the Groovy templating engine.

spring-boot-starter-hateoas

Support for HATEOAS-based RESTful services via spring-hateoas.

spring-boot-starter-hornetq

Support for “Java Message Service API” via HornetQ.

spring-boot-starter-integration

Support for common spring-integration modules.

spring-boot-starter-jdbc

Support for JDBC databases.

spring-boot-starter-jersey

Support for the Jersey RESTful Web Services framework.

spring-boot-starter-jta-atomikos

Support for JTA distributed transactions via Atomikos.

spring-boot-starter-jta-bitronix

Support for JTA distributed transactions via Bitronix.

spring-boot-starter-mail

Support for javax.mail.

spring-boot-starter-mobile

Support for spring-mobile.

spring-boot-starter-mustache

Support for the Mustache templating engine.

spring-boot-starter-redis

Support for the REDIS key-value data store, including spring-redis.

spring-boot-starter-security

Support for spring-security.

spring-boot-starter-social-facebook

Support for spring-social-facebook.

spring-boot-starter-social-linkedin

Support for spring-social-linkedin.

spring-boot-starter-social-twitter

Support for spring-social-twitter.

spring-boot-starter-test

Support for common test dependencies, including JUnit, Hamcrest and Mockito along with the spring-test module.

spring-boot-starter-thymeleaf

Support for the Thymeleaf templating engine, including integration with Spring.

spring-boot-starter-velocity

Support for the Velocity templating engine.

spring-boot-starter-web

Support for full-stack web development, including Tomcat and spring-webmvc.

spring-boot-starter-websocket

Support for WebSocket development.

spring-boot-starter-ws

Support for Spring Web Services.


In addition to the application starters, the following starters can be used to add production ready features.

Table 13.2. Spring Boot production ready starters

NameDescription

spring-boot-starter-actuator

Adds production ready features such as metrics and monitoring.

spring-boot-starter-remote-shell

Adds remote ssh shell support.


Finally, Spring Boot includes some starters that can be used if you want to exclude or swap specific technical facets.

Table 13.3. Spring Boot technical starters

NameDescription

spring-boot-starter-jetty

Imports the Jetty HTTP engine (to be used as an alternative to Tomcat).

spring-boot-starter-log4j

Support the Log4J logging framework.

spring-boot-starter-logging

Import Spring Boot’s default logging framework (Logback).

spring-boot-starter-tomcat

Import Spring Boot’s default HTTP engine (Tomcat).

spring-boot-starter-undertow

Imports the Undertow HTTP engine (to be used as an alternative to Tomcat).


[Tip]Tip

For a list of additional community contributed starter POMs, see the README file in the spring-boot-starters module on GitHub.

14. Structuring your code

Spring Boot does not require any specific code layout to work, however, there are some best practices that help.

14.1 Using the “default” package

When a class doesn’t 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 @ComponentScan, @EntityScan or @SpringBootApplication annotations, since every class from every jar, will be read.

[Tip]Tip

We recommend that you follow Java’s recommended package naming conventions and use a reversed domain name (for example, com.example.project).

14.2 Locating the main application class

We generally recommend that you locate your main application class in a root package above other classes. The @EnableAutoConfiguration 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 @EnableAutoConfiguration annotated class will be used to search for @Entity items.

Using a root package also allows the @ComponentScan annotation to be used without needing to specify a basePackage attribute. You can also use the @SpringBootApplication annotation if your main class is in the root package.

Here is a typical layout:

com
 +- example
     +- myproject
         +- Application.java
         |
         +- domain
         |   +- Customer.java
         |   +- CustomerRepository.java
         |
         +- service
         |   +- CustomerService.java
         |
         +- web
             +- CustomerController.java

The Application.java file would declare the main method, along with the basic @Configuration.

package com.example.myproject;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.EnableAutoConfiguration;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;

@Configuration
@EnableAutoConfiguration
@ComponentScan
public class Application {

    public static void main(String[] args) {
        SpringApplication.run(Application.class, args);
    }

}

15. Configuration classes

Spring Boot favors Java-based configuration. Although it is possible to call SpringApplication.run() with an XML source, we generally recommend that your primary source is a @Configuration class. Usually the class that defines the main method is also a good candidate as the primary @Configuration.

[Tip]Tip

Many Spring configuration examples have been published on the Internet that use XML configuration. Always try to use the equivalent Java-base configuration if possible. Searching for enable* annotations can be a good starting point.

15.1 Importing additional configuration classes

You don’t need to 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 pickup all Spring components, including @Configuration classes.

15.2 Importing XML configuration

If you absolutely must use XML based configuration, we recommend that you still start with a @Configuration class. You can then use an additional @ImportResource annotation to load XML configuration files.

16. Auto-configuration

Spring Boot auto-configuration attempts to automatically configure your Spring application based on the jar dependencies that you have added. For example, If HSQLDB is on your classpath, and you have not manually configured any database connection beans, then we will auto-configure 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]Tip

You should only ever add one @EnableAutoConfiguration annotation. We generally recommend that you add it to your primary @Configuration class.

16.1 Gradually replacing auto-configuration

Auto-configuration is noninvasive, 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 will back away.

If you need to find out what auto-configuration is currently being applied, and why, starting your application with the --debug switch. This will log an auto-configuration report to the console.

16.2 Disabling specific auto-configuration

If you find that specific auto-configure classes are being applied that you don’t want, you can use the exclude attribute of @EnableAutoConfiguration to disable them.

import org.springframework.boot.autoconfigure.*;
import org.springframework.boot.autoconfigure.jdbc.*;
import org.springframework.context.annotation.*;

@Configuration
@EnableAutoConfiguration(exclude={DataSourceAutoConfiguration.class})
public class MyConfiguration {
}

17. Spring Beans and dependency injection

You are free to use any of the standard Spring Framework techniques to define your beans and their injected dependencies. For simplicity, we often find that using @ComponentScan to find your beans, in combination with @Autowired 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.) will be automatically registered as Spring Beans.

Here is an example @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;
    }

    // ...

}
[Tip]Tip

Notice how using constructor injection allows the riskAssessor field to be marked as final, indicating that it cannot be subsequently changed.

18. Using the @SpringBootApplication annotation

Many Spring Boot developers always have their main class annotated with @Configuration, @EnableAutoConfiguration and @ComponentScan. Since these annotations are so frequently used together (especially if you follow the best practices above), Spring Boot provides a convenient @SpringBootApplication alternative.

The @SpringBootApplication annotation is equivalent to using @Configuration, @EnableAutoConfiguration and @ComponentScan with their default attributes:

package com.example.myproject;

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);
    }

}

19. Running your application

One of the biggest advantages of packaging your application as jar and using an embedded HTTP server is that you can run your application as you would any other. Debugging Spring Boot applications is also easy; you don’t need any special IDE plugins or extensions.

[Note]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.

19.1 Running from an IDE

You can run a Spring Boot application from your IDE as a simple Java application, however, first you will need to import your project. Import steps will 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 can’t directly import your project into your IDE, you may be able to generate IDE metadata using a build plugin. Maven includes plugins for Eclipse and IDEA; Gradle offers plugins for various IDEs.

[Tip]Tip

If you accidentally run a web application twice you will see a “Port already in use” error. STS users can use the Relaunch button rather than Run to ensure that any existing instance is closed.

19.2 Running as a packaged application

If you use the Spring Boot Maven or Gradle plugins to create an executable jar you can run your application using java -jar. For example:

$ java -jar target/myproject-0.0.1-SNAPSHOT.jar

It is also possible to run a packaged application with remote debugging support enabled. This allows you to attach a debugger to your packaged application:

$ java -Xdebug -Xrunjdwp:server=y,transport=dt_socket,address=8000,suspend=n \
       -jar target/myproject-0.0.1-SNAPSHOT.jar

19.3 Using the Maven plugin

The Spring Boot Maven plugin includes a run goal which can be used to quickly compile and run your application. Applications run in an exploded form, and you can edit resources for instant “hot” reload.

$ mvn spring-boot:run

You might also want to use the useful operating system environment variable:

$ export MAVEN_OPTS=-Xmx1024m -XX:MaxPermSize=128M -Djava.security.egd=file:/dev/./urandom

(The “egd” setting is to speed up Tomcat startup by giving it a faster source of entropy for session keys.)

19.4 Using the Gradle plugin

The Spring Boot Gradle plugin also includes a run goal which can be used to run your application in an exploded form. The bootRun task is added whenever you import the spring-boot-plugin

$ gradle bootRun

You might also want to use this useful operating system environment variable:

$ export JAVA_OPTS=-Xmx1024m -XX:MaxPermSize=128M -Djava.security.egd=file:/dev/./urandom

19.5 Hot swapping

Since Spring Boot applications are just plain Java applications, JVM hot-swapping should work out of the box. JVM hot swapping is somewhat limited with the bytecode that it can replace, for a more complete solution JRebel or the Spring Loaded project can be used. The spring-boot-devtools module also includes support for quick application restarts.

See the Chapter 20, Developer tools section below and the Hot swapping “How-to” for details.

20. Developer tools

Spring Boot includes an additional set of tools that can make the application development experience a little more pleasant. The spring-boot-devtools module can be included in any project to provide additional development-time features. To include devtools support, simply add the module dependency to your build:

Maven. 

<dependencies>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-devtools</artifactId>
    </dependency>
</dependencies>

Gradle. 

dependencies {
    compile("org.springframework.boot:spring-boot-devtools")
}

[Note]Note

Developer tools are automatically disabled when running a fully packaged application. If your application is launched using java -jar or if it’s started using a special classloader, then it is considered a “production application”.

20.1 Property defaults

Several of the libraries supported by Spring Boot use caches to improve performance. For example, Thymeleaf will cache templates to save repeatedly parsing XML source files. Whilst caching is very beneficial in production, it can be counter productive during development. If you make a change to a template file in your IDE, you’ll likely want to immediately see the result.

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 will automatically apply sensible development-time configuration.

[Tip]Tip

For a complete list of the properties that are applied see DevToolsPropertyDefaultsPostProcessor.

20.2 Automatic restart

Applications that use spring-boot-devtools will 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 will be monitored for changes.

[Tip]Tip

Automatic restart works very well when used with LiveReload. See below for details.

20.2.1 Excluding resources

Certain resources don’t necessarily need to trigger a restart when they are changed. For example, Thymeleaf templates can just be edited in-place. By default changing resources in /META-INF/maven, /META-INF/resources ,/resources ,/static ,/public or /templates will not trigger a restart. 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:

spring.devtools.restart.exclude=static/**,public/**

20.2.2 Disabling restart

If you don’t want to use the restart feature you can disable it using the spring.devtools.restart.enabled property. In most cases you can set this in your application.properties (this will still initialize the restart classloader but it won’t watch for file changes).

If you need to completely disable restart support, for example, because it doesn’t work with a specific library, you need to set a System property before calling SpringApplication.run(…​). For example:

public static void main(String[] args) {
    System.setProperty("spring.devtools.restart.enabled", "false");
    SpringApplication.run(MyApp.class, args);
}

20.2.3 Using a trigger file

If you work with an IDE that continuously compiles changed files, you might prefer to trigger restarts only at specific times. To do this you can use a “trigger file”, which is a special file that must be modified when you want to actually trigger a restart check. The trigger file could be updated manually, or via an IDE plugin.

To use a trigger file use the spring.devtools.restart.trigger-file property.

[Tip]Tip

You might want to set spring.devtools.restart.trigger-file as a global setting so that all your projects behave in the same way.

20.3 LiveReload

The spring-boot-devtools module includes an embedded LiveReload server that can be used to trigger a browser refresh when a resource is changed. LiveReload browser extensions are freely available for Chrome, Firefox and Safari from livereload.com.

If you don’t want to start the LiveReload server when your application runs you can set the spring.devtools.livereload.enabled property to false.

[Note]Note

You can only run one LiveReload server at a time, if you start multiple applications from your IDE only the first will have livereload support.

20.4 Global settings

You can configure global devtools settings by adding a file named .spring-boot-devtools.properties to your $HOME folder (note that the filename starts with “.”). Any properties added to this file will 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:

~/.spring-boot-devtools.properties. 

spring.devtools.reload.trigger-file=.reloadtrigger

20.5 Remote applications

The Spring Boot developer tools are not just limited to local development. You can also use several features when running applications remotely. Remote support is opt-in, to enable it you need to set a spring.devtools.remote.secret property. For example:

spring.devtools.remote.secret=mysecret
[Warning]Warning

Enabling spring-boot-devtools on a remote application is a security risk. You should never enable support on a production deployment.

Remote devtools support is provided in two parts; there is 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.

20.5.1 Running the remote client application

The remote client application is designed to be run from within you IDE. You need to run org.springframework.boot.devtools.RemoteSpringApplication using the same classpath as the remote project that you’re connecting to. The non-option argument passed to the application should be the remote URL that you are connecting to.

For example, if you are using Eclipse or STS, and you have a project named my-app that you’ve deployed to Cloud Foundry, you would do the following:

  • Select Run Configurations…​ from the Run menu.
  • Create a new Java Application “launch configuration”.
  • Browse for the my-app project.
  • Use org.springframework.boot.devtools.RemoteSpringApplication as the main class.
  • Add https://myapp.cfapps.io to the Program arguments (or whatever your remote URL is).

A running remote client will look like this:

  .   ____          _                                              __ _ _
 /\\ / ___'_ __ _ _(_)_ __  __ _          ___               _      \ \ \ \
( ( )\___ | '_ | '_| | '_ \/ _` |        | _ \___ _ __  ___| |_ ___ \ \ \ \
 \\/  ___)| |_)| | | | | || (_| []::::::[]   / -_) '  \/ _ \  _/ -_) ) ) ) )
  '  |____| .__|_| |_|_| |_\__, |        |_|_\___|_|_|_\___/\__\___|/ / / /
 =========|_|==============|___/===================================/_/_/_/
 :: Spring Boot Remote :: 1.3.0.BUILD-SNAPSHOT

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]Note

Because the remote client is using the same classpath as the real application it can directly read application properties. This is how the spring.devtools.remote.secret property is read and passed to the server for authentication.

[Tip]Tip

It’s always advisable to use https:// as the connection protocol so that traffic is encrypted and passwords cannot be intercepted.

20.5.2 Remote update

The remote client will monitor your application classpath for changes in the same way as the local restart. Any updated resource will be pushed to the remote application and (if required) trigger a restart. This can be quite helpful if you are iterating on a feature that uses a cloud service that you don’t have locally. Generally remote updates and restarts are much quicker than a full rebuild and deploy cycle.

[Note]Note

Files are only monitored when the remote client is running. If you change a file before starting the remote client, it won’t be pushed to the remote server.

20.5.3 Remote debug tunnel

Java remote debugging is useful when diagnosing issues on a remote application. Unfortunately, it’s not always possible to enable remote debugging when your application is deployed outside of your data center. Remote debugging can also be tricky to setup if you are using a container based technology such as Docker.

To help work around these limitations, devtools supports tunneling of remote debug traffic over HTTP. The remote client provides a local server on port 8000 that you can attach a remote debugger to. Once a connection is established, debug traffic is sent over HTTP to the remote application. You can use the spring.devtools.remote.debug.local-port property if you want to use a different port.

You’ll need to ensure that your remote application is started with remote debugging enabled. Often this can be achieved by configuring JAVA_OPTS. For example, with Cloud Foundry you can add the following to your manifest.yml:

---
  env:
    JAVA_OPTS: "-Xdebug -Xrunjdwp:server=y,transport=dt_socket,suspend=n"
[Tip]Tip

Notice that you don’t need to pass an address=NNNN option to -Xrunjdwp. If omitted Java will simply pick a random free port.

[Note]Note

Debugging a remote service over the Internet can be slow and you might need to increase timeouts in your IDE. For example, in Eclipse you can select JavaDebug from Preferences…​ and change the Debugger timeout (ms) to a more suitable value (60000 works well in most situations).

21. Packaging your application for production

Executable jars can be used for production deployment. As they are self-contained, they are also ideally suited for cloud-based deployment.

For additional “production ready” features, such as health, auditing and metric REST or JMX end-points; consider adding spring-boot-actuator. See Part V, “Spring Boot Actuator: Production-ready features” for details.

22. What to read next

You should now have good understanding of how you can use Spring Boot along with 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.

Part IV. Spring Boot features

This section dives into the details of Spring Boot. Here you can learn about the key features that you will want to use and customize. If you haven’t already, 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.

23. SpringApplication

The SpringApplication class provides a convenient way to bootstrap a Spring application that will be started from a main() method. In many situations you can just delegate to the static SpringApplication.run method:

public static void main(String[] args) {
    SpringApplication.run(MySpringConfiguration.class, args);
}

When your application starts you should see something similar to the following:

  .   ____          _            __ _ _
 /\\ / ___'_ __ _ _(_)_ __  __ _ \ \ \ \
( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \
 \\/  ___)| |_)| | | | | || (_| |  ) ) ) )
  '  |____| .__|_| |_|_| |_\__, | / / / /
 =========|_|==============|___/=/_/_/_/
 :: Spring Boot ::   v1.3.0.BUILD-SNAPSHOT

2013-07-31 00:08:16.117  INFO 56603 --- [           main] o.s.b.s.app.SampleApplication            : Starting SampleApplication v0.1.0 on mycomputer with PID 56603 (/apps/myapp.jar started by pwebb)
2013-07-31 00:08:16.166  INFO 56603 --- [           main] ationConfigEmbeddedWebApplicationContext : Refreshing org.springframework.boot.context.embedded.AnnotationConfigEmbeddedWebApplicationContext@6e5a8246: startup date [Wed Jul 31 00:08:16 PDT 2013]; root of context hierarchy
2014-03-04 13:09:54.912  INFO 41370 --- [           main] .t.TomcatEmbeddedServletContainerFactory : Server initialized with port: 8080
2014-03-04 13:09:56.501  INFO 41370 --- [           main] o.s.b.s.app.SampleApplication            : Started SampleApplication in 2.992 seconds (JVM running for 3.658)

By default INFO logging messages will be shown, including some relevant startup details such as the user that launched the application.

23.1 Customizing the Banner

The banner that is printed on start up can be changed by adding a banner.txt file to your classpath, or by setting banner.location to the location of such a file. If the file has an unusual encoding you can set banner.charset (default is UTF-8).

You can use the following variables inside your banner.txt file:

Table 23.1. Banner variables

VariableDescription

${application.version}

The version number of your application as declared in MANIFEST.MF. For example 1.0.

${application.formatted-version}

The version number of your application as declared in MANIFEST.MF formatted for display (surrounded with brackets and prefixed with v). For example (v1.0).

${spring-boot.version}

The Spring Boot version that you are using. For example 1.3.0.BUILD-SNAPSHOT.

${spring-boot.formatted-version}

The Spring Boot version that you are using formatted for display (surrounded with brackets and prefixed with v). For example (v1.3.0.BUILD-SNAPSHOT).

${Ansi.NAME},

Where NAME is the name of an ANSI escape code. See AnsiPropertySource for details.


[Tip]Tip

The SpringBootApplication.setBanner(…​) method can be used if you want to generate a banner programmatically. Use the org.springframework.boot.Banner interface and implement your own printBanner() method.

23.2 Customizing SpringApplication

If the SpringApplication defaults aren’t to your taste you can instead create a local instance and customize it. For example, to turn off the banner you would write:

public static void main(String[] args) {
    SpringApplication app = new SpringApplication(MySpringConfiguration.class);
    app.setShowBanner(false);
    app.run(args);
}
[Note]Note

The constructor arguments passed to SpringApplication are configuration sources for spring beans. In most cases these will be references to @Configuration classes, but they could also be references to XML configuration or to packages that should be scanned.

It is also possible to configure the SpringApplication using an application.properties file. See Chapter 24, Externalized Configuration for details.

For a complete list of the configuration options, see the SpringApplication Javadoc.

23.3 Fluent builder API

If you need to build an ApplicationContext hierarchy (multiple contexts with a parent/child relationship), or if you just prefer using a ‘fluent’ builder API, you can use the SpringApplicationBuilder.

The SpringApplicationBuilder allows you to chain together multiple method calls, and includes parent and child methods that allow you to create a hierarchy.

For example:

new SpringApplicationBuilder()
    .showBanner(false)
    .sources(Parent.class)
    .child(Application.class)
    .run(args);
[Note]Note

There are some restrictions when creating an ApplicationContext hierarchy, e.g. Web components must be contained within the child context, and the same Environment will be used for both parent and child contexts. See the SpringApplicationBuilder Javadoc for full details.

23.4 Application events and listeners

In addition to the usual Spring Framework events, such as ContextRefreshedEvent, a SpringApplication sends some additional application events. Some events are actually triggered before the ApplicationContext is created.

You can register event listeners in a number of ways, the most common being SpringApplication.addListeners(…​) method.

Application events are sent in the following order, as your application runs:

  1. An ApplicationStartedEvent is sent at the start of a run, but before any processing except the registration of listeners and initializers.
  2. An ApplicationEnvironmentPreparedEvent is sent when the Environment to be used in the context is known, but before the context is created.
  3. An ApplicationPreparedEvent is sent just before the refresh is started, but after bean definitions have been loaded.
  4. An ApplicationReadyEvent is sent after the refresh and any related callbacks have been processed to indicate the application is ready to service requests.
  5. An ApplicationFailedEvent is sent if there is an exception on startup.
[Tip]Tip

You often won’t need to use application events, but it can be handy to know that they exist. Internally, Spring Boot uses events to handle a variety of tasks.

23.5 Web environment

A SpringApplication will attempt to create the right type of ApplicationContext on your behalf. By default, an AnnotationConfigApplicationContext or AnnotationConfigEmbeddedWebApplicationContext will be used, depending on whether you are developing a web application or not.

The algorithm used to determine a ‘web environment’ is fairly simplistic (based on the presence of a few classes). You can use setWebEnvironment(boolean webEnvironment) if you need to override the default.

It is also possible to take complete control of the ApplicationContext type that will be used by calling setApplicationContextClass(…​).

[Tip]Tip

It is often desirable to call setWebEnvironment(false) when using SpringApplication within a JUnit test.

23.6 Using the CommandLineRunner

If you want access to the raw command line arguments, or you need to run some specific code once the SpringApplication has started you can implement the CommandLineRunner interface. The run(String…​ args) method will be called on all Spring beans implementing this interface.

import org.springframework.boot.*
import org.springframework.stereotype.*

@Component
public class MyBean implements CommandLineRunner {

    public void run(String... args) {
        // Do something...
    }

}

You can additionally implement the org.springframework.core.Ordered interface or use the org.springframework.core.annotation.Order annotation if several CommandLineRunner beans are defined that must be called in a specific order.

23.7 Application exit

Each SpringApplication will register a shutdown hook with the JVM to ensure that the ApplicationContext is closed 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 the application ends.

23.8 Admin features

It is possible to enable admin-related features for the application by specifying the spring.application.admin.enabled property. This exposes the SpringApplicationAdminMXBean on the platform MBeanServer. You could use this feature to administer your Spring Boot application remotely. This could also be useful for any service wrapper implementation.

[Tip]Tip

If you want to know on which HTTP port the application is running, get the property with key local.server.port.

[Note]Note

Take care when enabling this feature as the MBean exposes a method to shutdown the application.

24. Externalized Configuration

Spring Boot allows you to externalize your configuration so 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 using the @Value annotation, accessed via Spring’s Environment abstraction or bound to structured objects.

Spring Boot uses a very particular PropertySource order that is designed to allow sensible overriding of values, properties are considered in the the following order:

  1. Command line arguments.
  2. JNDI attributes from java:comp/env.
  3. Java System properties (System.getProperties()).
  4. OS environment variables.
  5. A RandomValuePropertySource that only has properties in random.*.
  6. Profile-specific application properties outside of your packaged jar (application-{profile}.properties and YAML variants)
  7. Profile-specific application properties packaged inside your jar (application-{profile}.properties and YAML variants)
  8. Application properties outside of your packaged jar (application.properties and YAML variants).
  9. Application properties packaged inside your jar (application.properties and YAML variants).
  10. @PropertySource annotations on your @Configuration classes.
  11. Default properties (specified using SpringApplication.setDefaultProperties).

To provide a concrete example, suppose you develop a @Component that uses a name property:

import org.springframework.stereotype.*
import org.springframework.beans.factory.annotation.*

@Component
public class MyBean {

    @Value("${name}")
    private String name;

    // ...

}

You can bundle an application.properties inside your jar that provides a sensible default name. When running in production, an application.properties can be provided outside of your jar that overrides name; and for one-off testing, you can launch with a specific command line switch (e.g. java -jar app.jar --name="Spring").

24.1 Configuring random values

The RandomValuePropertySource is useful for injecting random values (e.g. into secrets or test cases). It can produce integers, longs or strings, e.g.

my.secret=${random.value}
my.number=${random.int}
my.bignumber=${random.long}
my.number.less.than.ten=${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 (exclusive).

24.2 Accessing command line properties

By default SpringApplication will convert any command line option arguments (starting with ‘--’, e.g. --server.port=9000) to a property and add it to the Spring Environment. As mentioned above, command line properties always take precedence over other property sources.

If you don’t want command line properties to be added to the Environment you can disable them using SpringApplication.setAddCommandLineProperties(false).

24.3 Application property files

SpringApplication will load properties from application.properties files in the following locations and add them to the Spring Environment:

  1. A /config subdir of the current directory.
  2. The current directory
  3. A classpath /config package
  4. The classpath root

The list is ordered by precedence (locations higher in the list override lower items).

[Note]Note

You can also use YAML ('.yml') files as an alternative to '.properties'.

If you don’t like application.properties as the configuration file name you can switch to another by specifying a spring.config.name environment property. You can also refer to an explicit location using the spring.config.location environment property (comma-separated list of directory locations, or file paths).

$ java -jar myproject.jar --spring.config.name=myproject

or

$ java -jar myproject.jar --spring.config.location=classpath:/default.properties,classpath:/override.properties

If spring.config.location contains directories (as opposed to files) they should end in / (and will be appended with the names generated from spring.config.name before being loaded). The default search path classpath:,classpath:/config,file:,file:config/ is always used, irrespective of the value of spring.config.location. In that way you can set up default values for your application in application.properties (or whatever other basename you choose with spring.config.name) and override it at runtime with a different file, keeping the defaults.

[Note]Note

If you use environment variables rather than system properties, most operating systems disallow period-separated key names, but you can use underscores instead (e.g. SPRING_CONFIG_NAME instead of spring.config.name).

[Note]Note

If you are running in a container then JNDI properties (in java:comp/env) or servlet context initialization parameters can be used instead of, or as well as, environment variables or system properties.

24.4 Profile-specific properties

In addition to application.properties files, profile-specific properties can also be defined using the naming convention application-{profile}.properties. The Environment has a set of default profiles (by default [default]) which are used if no active profiels are set (i.e. 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 irrespective of whether the profile-specific files are inside or outside your packaged jar.

24.5 Placeholders in properties

The values in application.properties are filtered through the existing Environment when they are used so you can refer back to previously defined values (e.g. from System properties).

app.name=MyApp
app.description=${app.name} is a Spring Boot application
[Tip]Tip

You can also use this technique to create ‘short’ variants of existing Spring Boot properties. See the Section 67.3, “Use ‘short’ command line arguments” how-to for details.

24.6 Using YAML instead of Properties

YAML is a superset of JSON, and as such is a very convenient format for specifying hierarchical configuration data. The SpringApplication class will automatically support YAML as an alternative to properties whenever you have the SnakeYAML library on your classpath.

[Note]Note

If you use ‘starter POMs’ SnakeYAML will be automatically provided via spring-boot-starter.

24.6.1 Loading YAML

Spring Framework provides two convenient classes that can be used to load YAML documents. The YamlPropertiesFactoryBean will load YAML as Properties and the YamlMapFactoryBean will load YAML as a Map.

For example, the following YAML document:

environments:
    dev:
        url: http://dev.bar.com
        name: Developer Setup
    prod:
        url: http://foo.bar.com
        name: My Cool App

Would be transformed into these properties:

environments.dev.url=http://dev.bar.com
environments.dev.name=Developer Setup
environments.prod.url=http://foo.bar.com
environments.prod.name=My Cool App

YAML lists are represented as property keys with [index] dereferencers, for example this YAML:

my:
   servers:
       - dev.bar.com
       - foo.bar.com

Would be transformed into these properties:

my.servers[0]=dev.bar.com
my.servers[1]=foo.bar.com

To bind to properties like that using the Spring DataBinder 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, e.g. this will bind to the properties above

@ConfigurationProperties(prefix="my")
public class Config {

    private List<String> servers = new ArrayList<String>();

    public List<String> getServers() {
        return this.servers;
    }
}

24.6.2 Exposing YAML as properties in the Spring Environment

The YamlPropertySourceLoader class can be used to expose YAML as a PropertySource in the Spring Environment. This allows you to use the familiar @Value annotation with placeholders syntax to access YAML properties.

24.6.3 Multi-profile YAML documents

You can specify multiple profile-specific YAML documents in a single file by using a spring.profiles key to indicate when the document applies. For example:

server:
    address: 192.168.1.100
---
spring:
    profiles: development
server:
    address: 127.0.0.1
---
spring:
    profiles: production
server:
    address: 192.168.1.120

In the example above, the server.address property will be 127.0.0.1 if the development profile is active. If the development and production profiles are not enabled, then the value for the property will be 192.168.1.100.

The default profiles are activated if none are explicitly active when the application context starts. So in this YAML we set a value for security.user.password that is only available in the "default" profile:

server:
  port: 80000
---
spring:
  profiles: default
security:
  user:
    password: weak

whereas in this example, the password is always set because it isn’t attached to any profile, and it would have to be explicitly reset in all other profiles as necessary:

server:
  port: 80000
security:
  user:
    password: weak

24.6.4 YAML shortcomings

YAML files can’t be loaded via the @PropertySource annotation. So in the case that you need to load values that way, you need to use a properties file.

24.7 Typesafe Configuration Properties

Using the @Value("${property}") annotation to inject configuration properties can sometimes be cumbersome, especially if you are working with multiple properties or your data is hierarchical in nature. Spring Boot provides an alternative method of working with properties that allows strongly typed beans to govern and validate the configuration of your application. For example:

@Component
@ConfigurationProperties(prefix="connection")
public class ConnectionSettings {

    private String username;

    private InetAddress remoteAddress;

    // ... getters and setters

}
[Note]Note

The getters and setters are advisable, since binding is via standard Java Beans property descriptors, just like in Spring MVC. They are mandatory for immutable types or those that are directly coercible from String. As long as they are initialized, maps, collections, and arrays need a getter but not necessarily a setter since they can be mutated by the binder. If there is a setter, Maps, collections, and arrays can be created. Maps and collections can be expanded with only a getter, whereas arrays require a setter. Nested POJO properties can also be created (so a setter is not mandatory) if they have a default constructor, or a constructor accepting a single value that can be coerced from String. Some people use Project Lombok to add getters and setters automatically.

When the @EnableConfigurationProperties annotation is applied to your @Configuration, any beans annotated with @ConfigurationProperties will be automatically configured from the Environment properties. This style of configuration works particularly well with the SpringApplication external YAML configuration:

# application.yml

connection:
    username: admin
    remoteAddress: 192.168.1.1

# additional configuration as required

To work with @ConfigurationProperties beans you can just inject them in the same way as any other bean.

@Service
public class MyService {

    @Autowired
    private ConnectionSettings connection;

     //...

    @PostConstruct
    public void openConnection() {
        Server server = new Server();
        this.connection.configure(server);
    }

}

It is also possible to shortcut the registration of @ConfigurationProperties bean definitions by simply listing the properties classes directly in the @EnableConfigurationProperties annotation:

@Configuration
@EnableConfigurationProperties(ConnectionSettings.class)
public class MyConfiguration {
}
[Tip]Tip

Using @ConfigurationProperties also allows you to generate meta-data files that can be used by IDEs. See the Appendix B, Configuration meta-data appendix for details.

24.7.1 Third-party configuration

As well as using @ConfigurationProperties to annotate a class, you can also use it on @Bean methods. This 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:

@ConfigurationProperties(prefix = "foo")
@Bean
public FooComponent fooComponent() {
    ...
}

Any property defined with the foo prefix will be mapped onto that FooComponent bean in a similar manner as the ConnectionSettings example above.

24.7.2 Relaxed binding

Spring Boot uses some relaxed rules for binding Environment properties to @ConfigurationProperties beans, so there doesn’t need to be an exact match between the Environment property name and the bean property name. Common examples where this is useful include dashed separated (e.g. context-path binds to contextPath), and capitalized (e.g. PORT binds to port) environment properties.

For example, given the following @ConfigurationProperties class:

@Component
@ConfigurationProperties(prefix="person")
public class ConnectionSettings {

    private String firstName;

    public String getFirstName() {
        return this.firstName;
    }

    public void setFirstName(String firstName) {
        this.firstName = firstName;
    }

}

The following properties names can all be used:

Table 24.1. relaxed binding

PropertyNote

person.firstName

Standard camel case syntax.

person.first-name

Dashed notation, recommended for use in .properties and .yml files.

PERSON_FIRST_NAME

Upper case format. Recommended when using a system environment variables.


Spring will attempt 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 bean id conversionService) or custom property editors (via a CustomEditorConfigurer bean).

24.7.3 @ConfigurationProperties Validation

Spring Boot will attempt to validate external configuration, by default using JSR-303 (if it is on the classpath). You can simply add JSR-303 javax.validation constraint annotations to your @ConfigurationProperties class:

@Component
@ConfigurationProperties(prefix="connection")
public class ConnectionSettings {

    @NotNull
    private InetAddress remoteAddress;

    // ... getters and setters

}

You can also add a custom Spring Validator by creating a bean definition called configurationPropertiesValidator.

[Tip]Tip

The spring-boot-actuator module includes an endpoint that exposes all @ConfigurationProperties beans. Simply point your web browser to /configprops or use the equivalent JMX endpoint. See the Production ready features. section for details.

25. Profiles

Spring Profiles provide a way to segregate parts of your application configuration and make it only available in certain environments. Any @Component or @Configuration can be marked with @Profile to limit when it is loaded:

@Configuration
@Profile("production")
public class ProductionConfiguration {

    // ...

}

In the normal Spring way, you can use a spring.profiles.active Environment property to specify which profiles are active. You can specify the property in any of the usual ways, for example you could include it in your application.properties:

spring.profiles.active=dev,hsqldb

or specify on the command line using the switch --spring.profiles.active=dev,hsqldb.

25.1 Adding active profiles

The spring.profiles.active property follows the same ordering rules as other properties, the highest PropertySource will win. This means that you can specify active profiles in application.properties then replace them 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 (i.e. on top of those activated by the spring.profiles.active property): see the setAdditionalProfiles() method.

For example, when an application with following properties is run using the switch --spring.profiles.active=prod the proddb and prodmq profiles will also be activated:

---
my.property: fromyamlfile
---
spring.profiles: prod
spring.profiles.include: proddb,prodmq
[Note]Note

Remember that the spring.profiles property can be defined in a YAML document to determine when this particular document is included in the configuration. See Section 67.6, “Change configuration depending on the environment” for more details.

25.2 Programmatically setting profiles

You can programmatically set active profiles by calling SpringApplication.setAdditionalProfiles(…​) before your application runs. It is also possible to activate profiles using Spring’s ConfigurableEnvironment interface.

25.3 Profile specific configuration files

Profile specific variants of both application.properties (or application.yml) and files referenced via @ConfigurationProperties are considered as files are loaded. See Section 24.4, “Profile-specific properties” for details.

26. Logging

Spring Boot uses Commons Logging for all internal logging, but leaves the underlying log implementation open. Default configurations are provided for Java Util Logging, Log4J, 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 ‘Starter POMs’, Logback will be used for logging. Appropriate Logback routing is also included to ensure that dependent libraries that use Java Util Logging, Commons Logging, Log4J or SLF4J will all work correctly.

[Tip]Tip

There are a lot of logging frameworks available for Java. Don’t worry if the above list seems confusing. Generally you won’t need to change your logging dependencies and the Spring Boot defaults will work just fine.

26.1 Log format

The default log output from Spring Boot looks like this:

2014-03-05 10:57:51.112  INFO 45469 --- [           main] org.apache.catalina.core.StandardEngine  : Starting Servlet Engine: Apache Tomcat/7.0.52
2014-03-05 10:57:51.253  INFO 45469 --- [ost-startStop-1] o.a.c.c.C.[Tomcat].[localhost].[/]       : Initializing Spring embedded WebApplicationContext
2014-03-05 10:57:51.253  INFO 45469 --- [ost-startStop-1] o.s.web.context.ContextLoader            : Root WebApplicationContext: initialization completed in 1358 ms
2014-03-05 10:57:51.698  INFO 45469 --- [ost-startStop-1] o.s.b.c.e.ServletRegistrationBean        : Mapping servlet: 'dispatcherServlet' to [/]
2014-03-05 10:57:51.702  INFO 45469 --- [ost-startStop-1] o.s.b.c.embedded.FilterRegistrationBean  : Mapping filter: 'hiddenHttpMethodFilter' to: [/*]

The following items are output:

  • Date and Time — Millisecond precision and easily sortable.
  • Log Level — ERROR, WARN, INFO, DEBUG or TRACE.
  • Process ID.
  • A --- separator to distinguish the start of actual log messages.
  • Thread name — Enclosed in square brackets (may be truncated for console output).
  • Logger name — This is usually the source class name (often abbreviated).
  • The log message.

26.2 Console output

The default log configuration will echo messages to the console as they are written. By default ERROR, WARN and INFO level messages are logged. To also log DEBUG level messages to the console you can start your application with a --debug flag.

$ java -jar myapp.jar --debug
[Note]Note

you can also specify debug=true in your application.properties.

If your terminal supports ANSI, color output will be used to aid readability. You can set spring.output.ansi.enabled to a supported value to override the auto detection.

26.3 File output

By default, Spring Boot will only log to the console and will 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 26.1. Logging properties

logging.file

logging.path

Example

Description

(none)

(none)

 

Console only logging.

Specific file

(none)

my.log

Writes to the specified log file. Names can be an exact location or relative to the current directory.

(none)

Specific directory

/var/log

Writes spring.log to the specified directory. Names can be an exact location or relative to the current directory.


Log files will rotate when they reach 10 Mb and as with console output, ERROR, WARN and INFO level messages are logged by default.

[Note]Note

The logging system is initialized early in the application lifecycle and as such logging properties will not be found in property files loaded via @PropertySource annotations.

26.4 Log Levels

All the supported logging systems can have the logger levels set in the Spring Environment (so for example in application.properties) using ‘logging.level.*=LEVEL’ where ‘LEVEL’ is one of TRACE, DEBUG, INFO, WARN, ERROR, FATAL, OFF. Example application.properties:

logging.level.org.springframework.web=DEBUG
logging.level.org.hibernate=ERROR
[Note]Note

By default Spring Boot remaps Thymeleaf INFO messages so that they are logged at DEBUG level. This helps to reduce noise in the standard log output. See LevelRemappingAppender for details of how you can apply remapping in your own configuration.

26.5 Custom log configuration

The various logging systems can be activated by including the appropriate libraries on the classpath, and further customized by providing a suitable configuration file in the root of the classpath, or in a location specified by the Spring Environment property logging.config.

[Note]Note

Since logging is initialized before the ApplicationContext is created, it isn’t possible to control logging from @PropertySources in Spring @Configuration files. System properties and the conventional Spring Boot external configuration files work just fine.)

Depending on your logging system, the following files will be loaded:

Logging SystemCustomization

Logback

logback-spring.xml, logback-spring.groovy, logback.xml or logback.groovy

Log4j

log4j-spring.properties, log4j-spring.xml, log4j.properties or log4j.xml

Log4j2

log4j2-spring.xml or log4j2.xml

JDK (Java Util Logging)

logging.properties

[Note]Note

When possible we recommend that you use the -spring variants for your logging configuration (for example logback-spring.xml rather than logback.xml). If you use standard configuration locations, Spring cannot completely control log initialization.

[Warning]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 if at all possible.

To help with the customization some other properties are transferred from the Spring Environment to System properties:

Spring EnvironmentSystem PropertyComments

logging.file

LOG_FILE

Used in default log configuration if defined.

logging.path

LOG_PATH

Used in default log configuration if defined.

PID

PID

The current process ID (discovered if possible and when not already defined as an OS environment variable).

All the logging systems supported can consult System properties when parsing their configuration files. See the default configurations in spring-boot.jar for examples.

26.6 Logback extensions

Spring Boot includes a number of extensions to Logback which can help with advanced configuration. You can use these extensions in your logback-spring.xml configuration file.

[Note]Note

You cannot use extensions in the standard logback.xml configuration file since it’s loaded too early. You need to either use logback-spring.xml or define a logging.config property.

26.6.1 Profile specific configuration

The <springProfile> tag allows you to 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.

<springProfile name="staging">
    <!-- configuration to be enabled when the "staging" profile is active -->
</springProfile>

<springProfile name="!production">
    <!-- configuration to be enabled when the "production" profile is not active -->
</springProfile>

26.6.2 Environment properties

The <springProperty> tag allows you to surface properties from the Spring Environment for use within Logback. This 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, but rather than specifying a direct value you specify the source of the property (from the Environment). You can use the scope attribute if you need to store the property somewhere other than in local scope.

<springProperty scope="context" name="fluentHost" source="myapp.fulentd.host"/>
<appender name="FLUENT" class="ch.qos.logback.more.appenders.DataFluentAppender">
    <remoteHost>${fluentHost}</remoteHost>
    ...
</appender>
[Tip]Tip

The RelaxedPropertyResolver is used to access Environment properties. If specify the source in dashed notation (my-property-name) all the relaxed variations will be tried (myPropertyName, MY_PROPERTY_NAME etc).

27. Developing web applications

Spring Boot is well suited for web application development. You can easily create a self-contained HTTP server using embedded Tomcat, Jetty, or Undertow. Most web applications will use the spring-boot-starter-web module to get up and running quickly.

If you haven’t yet developed a Spring Boot web application you can follow the "Hello World!" example in the Getting started section.

27.1 The ‘Spring Web MVC framework’

The Spring Web MVC framework (often referred to as simply ‘Spring MVC’) is a rich ‘model view controller’ web framework. Spring MVC lets you create special @Controller or @RestController beans to handle incoming HTTP requests. Methods in your controller are mapped to HTTP using @RequestMapping annotations.

Here is a typical example @RestController to serve 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 available at spring.io/guides that cover Spring MVC.

27.1.1 Spring MVC auto-configuration

Spring Boot provides auto-configuration for Spring MVC that works well with most applications.

The auto-configuration adds the following features on top of Spring’s defaults:

  • Inclusion of ContentNegotiatingViewResolver and BeanNameViewResolver beans.
  • Support for serving static resources, including support for WebJars (see below).
  • Automatic registration of Converter, GenericConverter, Formatter beans.
  • Support for HttpMessageConverters (see below).
  • Automatic registration of MessageCodesResolver (see below).
  • Static index.html support.
  • Custom Favicon support.

If you want to take complete control of Spring MVC, you can add your own @Configuration annotated with @EnableWebMvc. If you want to keep Spring Boot MVC features, and you just want to add additional MVC configuration (interceptors, formatters, view controllers etc.) you can add your own @Bean of type WebMvcConfigurerAdapter, but without @EnableWebMvc.

27.1.2 HttpMessageConverters

Spring MVC uses the HttpMessageConverter interface to convert HTTP requests and responses. Sensible defaults are included out of the box, for example Objects can be automatically converted to JSON (using the Jackson library) or XML (using the Jackson XML extension if available, else using JAXB). Strings are encoded using UTF-8 by default.

If you need to add or customize converters you can use Spring Boot’s HttpMessageConverters class:

import org.springframework.boot.autoconfigure.web.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 will be added to the list of converters. You can also override default converters that way.

27.1.3 MessageCodesResolver

Spring MVC has a strategy for generating error codes for rendering error messages from binding errors: MessageCodesResolver. Spring Boot will create one for you if you set the spring.mvc.message-codes-resolver.format property PREFIX_ERROR_CODE or POSTFIX_ERROR_CODE (see the enumeration in DefaultMessageCodesResolver.Format).

27.1.4 Static Content

By default Spring Boot will serve 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 you can modify that behavior by adding your own WebMvcConfigurerAdapter 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 will not happen (unless you modify the default MVC configuration) because Spring will always be able to handle requests through the DispatcherServlet.

You can customize the static resource locations using spring.resources.staticLocations (replacing the default values with a list of directory locations). If you do this the default welcome page detection will switch to your custom locations, so if there is an index.html in any of your locations on startup, it will be the home page of the application.

In addition to the ‘standard’ static resource locations above, a special case is made for Webjars content. Any resources with a path in /webjars/** will be served from jar files if they are packaged in the Webjars format.

[Tip]Tip

Do not use the src/main/webapp directory if your application will be packaged as a jar. Although this directory is a common standard, it will only work with war packaging and it will be silently ignored by most build tools if you generate a jar.

Spring Boot also supports advanced resource handling features provided by Spring MVC, allowing use cases such as cache busting static resources or using version agnostic URLs for Webjars.

For example, the following configuration will configure a cache busting solution for all static resources, effectively adding a content hash in URLs, such as <link href="/css/spring-2a2d595e6ed9a0b24f027f2b63b134d6.css"/>:

spring.resources.chain.strategy.content.enabled=true
spring.resources.chain.strategy.content.paths=/**
[Note]Note

Links to resources are rewritten at runtime in template, thanks to a ResourceUrlEncodingFilter, auto-configured for Thymeleaf and Velocity. You should manually declare this filter when using JSPs. Other template engines aren’t automatically supported right now, but can be with custom template macros/helpers and the use of the ResourceUrlProvider.

When loading resources dynamically with, for example, a JavaScript module loader, renaming files is not an option. That’s why other strategies are also supported and can be combined. A "fixed" strategy will add a static version string in the URL, without changing the file name:

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/" will use a fixed versioning strategy "/v12/js/lib/mymodule.js" while other resources will still use the content one <link href="/css/spring-2a2d595e6ed9a0b24f027f2b63b134d6.css"/>.

See ResourceProperties for more of the supported options.

[Tip]Tip

This feature has been thoroughly described in a dedicated blog post and in Spring Framework’s reference documentation.

27.1.5 Template engines

As well as REST web services, you can also use Spring MVC to serve dynamic HTML content. Spring MVC supports a variety of templating technologies including Velocity, FreeMarker and JSPs. Many other templating engines also ship their own Spring MVC integrations.

Spring Boot includes auto-configuration support for the following templating engines:

[Tip]Tip

JSPs should be avoided if possible, there are several known limitations when using them with embedded servlet containers.

When you’re using one of these templating engines with the default configuration, your templates will be picked up automatically from src/main/resources/templates.

[Tip]Tip

IntelliJ IDEA orders the classpath differently depending on how you run your application. Running your application in the IDE via its main method will result in a different ordering to when you run your application using Maven or Gradle or from its pacakaged jar. This can cause Spring Boot to fail to find the templates on the classpath. If you’re affected by this problem you can reorder the classpath in the IDE to place the module’s classes and resources first. Alternatively, you can configure the template prefix to search every templates directory on the classpath: classpath*:/templates/.

27.1.6 Error Handling

Spring Boot provides an /error mapping by default 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 will produce 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 just add a View that resolves to ‘error’). To replace the default behaviour completely you can implement ErrorController and register a bean definition of that type, or simply add a bean of type ErrorAttributes to use the existing mechanism but replace the contents.

If you want more specific error pages for some conditions, the embedded servlet containers support a uniform Java DSL for customizing the error handling. For example:

@Bean
public EmbeddedServletContainerCustomizer containerCustomizer(){
    return new MyCustomizer();
}

// ...

private static class MyCustomizer implements EmbeddedServletContainerCustomizer {

    @Override
    public void customize(ConfigurableEmbeddedServletContainer container) {
        container.addErrorPages(new ErrorPage(HttpStatus.BAD_REQUEST, "/400"));
    }

}

You can also use regular Spring MVC features like @ExceptionHandler methods and @ControllerAdvice. The ErrorController will then pick up any unhandled exceptions.

N.B. if you register an ErrorPage with a path that will end up being handled by a Filter (e.g. as is common with some non-Spring web frameworks, like Jersey and Wicket), then the Filter has to be explicitly registered as an ERROR dispatcher, e.g.

@Bean
public FilterRegistrationBean myFilter() {
    FilterRegistrationBean registration = new FilterRegistrationBean();
    registration.setFilter(new MyFilter());
    ...
    registration.setDispatcherTypes(EnumSet.allOf(DispatcherType.class));
    return registration;
}

(the default FilterRegistrationBean does not include the ERROR dispatcher type).

Error Handling on WebSphere Application Server

When deployed to a servlet container, a Spring Boot uses its error page filter to forward a request with an error status to the appropriate error page. The request can only be forwarded to the correct error page if the response has not already been committed. By default, WebSphere Application Server 8.0 and later commits the response upon successful completion of a servlet’s service method. You should disable this behaviour by setting com.ibm.ws.webcontainer.invokeFlushAfterService to false

27.1.7 Spring HATEOAS

If you’re developing 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 will be customized based on the spring.jackson.* properties or a Jackson2ObjectMapperBuilder bean if one exists.

You can take control of Spring HATEOAS’s configuration by using @EnableHypermediaSupport. Note that this will disable the ObjectMapper customization described above.

27.2 JAX-RS and Jersey

If you prefer the JAX-RS programming model for REST endpoints you can use one of the available implementations instead of Spring MVC. Jersey 1.x and Apache Celtix work quite well out of the box if you just register their Servlet or Filter as a @Bean in your application context. Jersey 2.x 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 2.x just 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:

@Component
public class JerseyConfig extends ResourceConfig {

    public JerseyConfig() {
        register(Endpoint.class);
    }

}

All the registered endpoints should be @Components with HTTP resource annotations (@GET etc.), e.g.

@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 @Autowired dependencies and inject external configuration with @Value. The Jersey servlet will be registered and mapped to /* by default. You can change the mapping by adding @ApplicationPath to your ResourceConfig.

By default Jersey will be set up as a Servlet in a @Bean of type ServletRegistrationBean named jerseyServletRegistration. 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 servlet has an @Order which you can set with spring.jersey.filter.order. Both the Servlet and the Filter registrations can be given init parameters using spring.jersey.init.* to specify a map of properties.

There is a Jersey sample so you can see how to set things up. There is also a Jersey 1.x sample. Note that in the Jersey 1.x sample that the spring-boot maven plugin has been configured to unpack some Jersey jars so they can be scanned by the JAX-RS implementation (because the sample asks for them to be scanned in its Filter registration). You may need to do the same if any of your JAX-RS resources are packages as nested jars.

27.3 Embedded servlet container support

Spring Boot includes support for embedded Tomcat, Jetty, and Undertow servers. Most developers will simply use the appropriate ‘Starter POM’ to obtain a fully configured instance. By default the embedded server will listen for HTTP requests on port 8080.

27.3.1 Servlets and Filters

When using an embedded servlet container you can register Servlets, Filters and all the listeners from the Servlet spec (e.g. HttpSessionListener) directly as Spring beans. 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 will be mapped to /. In the case of multiple Servlet beans the bean name will be used as a path prefix. Filters will map to /*.

If convention-based mapping is not flexible enough you can use the ServletRegistrationBean, FilterRegistrationBean and ServletListenerRegistrationBean classes for complete control. You can also register items directly if your bean implements the ServletContextInitializer interface.

27.3.2 The EmbeddedWebApplicationContext

Under the hood Spring Boot uses a new type of ApplicationContext for embedded servlet container support. The EmbeddedWebApplicationContext is a special type of WebApplicationContext that bootstraps itself by searching for a single EmbeddedServletContainerFactory bean. Usually a TomcatEmbeddedServletContainerFactory, JettyEmbeddedServletContainerFactory, or UndertowEmbeddedServletContainerFactory will have been auto-configured.

[Note]Note

You usually won’t need to be aware of these implementation classes. Most applications will be auto-configured and the appropriate ApplicationContext and EmbeddedServletContainerFactory will be created on your behalf.

27.3.3 Customizing embedded servlet containers

Common servlet container settings can be configured using Spring Environment properties. Usually you would define the properties in your application.properties file.

Common server settings include:

  • server.port — The listen port for incoming HTTP requests.
  • server.address — The interface address to bind to.
  • server.sessionTimeout — A session timeout.

See the ServerProperties class for a complete list.

Programmatic customization

If you need to configure your embdedded servlet container programmatically you can register a Spring bean that implements the EmbeddedServletContainerCustomizer interface. EmbeddedServletContainerCustomizer provides access to the ConfigurableEmbeddedServletContainer which includes numerous customization setter methods.

import org.springframework.boot.context.embedded.*;
import org.springframework.stereotype.Component;

@Component
public class CustomizationBean implements EmbeddedServletContainerCustomizer {

    @Override
    public void customize(ConfigurableEmbeddedServletContainer container) {
        container.setPort(9000);
    }

}

Customizing ConfigurableEmbeddedServletContainer directly

If the above customization techniques are too limited, you can register the TomcatEmbeddedServletContainerFactory, JettyEmbeddedServletContainerFactory or UndertowEmbeddedServletContainerFactory bean yourself.

@Bean
public EmbeddedServletContainerFactory servletContainer() {
    TomcatEmbeddedServletContainerFactory factory = new TomcatEmbeddedServletContainerFactory();
    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.

27.3.4 JSP limitations

When running a Spring Boot application that uses an embedded servlet container (and is packaged as an executable archive), there are some limitations in the JSP support.

  • With Tomcat it should work if you use war packaging, i.e. an executable war will work, and will also be deployable to a standard container (not limited to, but including Tomcat). An executable jar will not work because of a hard coded file pattern in Tomcat.
  • Jetty does not currently work as an embedded container with JSPs.
  • Undertow does not support JSPs.

There is a JSP sample so you can see how to set things up.

28. Security

If Spring Security is on the classpath then web applications will be secure by default with ‘basic’ authentication on all HTTP endpoints. 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.

The default AuthenticationManager has a single user (‘user’ username and random password, printed at INFO level when the application starts up)

Using default security password: 78fa095d-3f4c-48b1-ad50-e24c31d5cf35
[Note]Note

If you fine tune your logging configuration, ensure that the org.springframework.boot.autoconfigure.security category is set to log INFO messages, otherwise the default password will not be printed.

You can change the password by providing a security.user.password. This and other useful properties are externalized via SecurityProperties (properties prefix "security").

The default security configuration is implemented in SecurityAutoConfiguration and in the classes imported from there (SpringBootWebSecurityConfiguration for web security and AuthenticationManagerConfiguration for authentication configuration which is also relevant in non-web applications). To switch off the Boot default configuration completely in a web application you can add a bean with @EnableWebSecurity. To customize it you normally use external properties and beans of type WebSecurityConfigurerAdapter (e.g. to add form-based login). There are several secure applications in the Spring Boot samples to get you started with common use cases.

The basic features you get out of the box in a web application are:

  • An AuthenticationManager bean with in-memory store and a single user (see SecurityProperties.User for the properties of the user).
  • Ignored (unsecure) paths for common static resource locations (/css/**, /js/**, /images/** and **/favicon.ico).
  • HTTP Basic security for all other endpoints.
  • Security events published to Spring’s ApplicationEventPublisher (successful and unsuccessful authentication and access denied).
  • Common low-level features (HSTS, XSS, CSRF, caching) provided by Spring Security are on by default.

All of the above can be switched on and off or modified using external properties (security.*). To override the access rules without changing any other autoconfigured features add a @Bean of type WebSecurityConfigurerAdapter with @Order(SecurityProperties.ACCESS_OVERRIDE_ORDER).

28.1 OAuth2

If you have spring-security-oauth2 on your classpath you can take advantage of some auto-configuration to make it easy to set up Authorization or Resource Server.

28.1.1 Authorization Server

To create an Authorization Server and grant access tokens you need to use @EnableAuthorizationServer and provide spring.oauth2.client.client-id and spring.oauth2.client.client-secret] properties. The client will be registered for you in an in-memory repository.

Having done that you will be able to use the client credentials to create an access token, for example:

$ curl client:secret@localhost:8080/oauth/token -d grant_type=password -d username=user -d password=pwd

The basic auth credentials for the /token endpoint are the client-id and client-secret. The user credentials are the normal Spring Security user details (which default in Spring Boot to “user” and a random password).

To switch off the auto-configuration and configure the Authorization Server features yourself just add a @Bean of type AuthorizationServerConfigurer.

28.1.2 Resource Server

To use the access token you need a Resource Server (which can be the same as the Authorization Server). Creating a Resource Server is easy, just add @EnableResourceServer and provide some configuration to allow the server to decode access tokens. If your appplication is also an Authorization Server it already knows how to decode tokens, so there is nothing else to do. If your app is a standalone service then you need to give it some more configuration, one of the following options:

If you specify both the user-info-uri and the token-info-uri then you can set a flag to say that one is preferred over the other (prefer-token-info=true is the default).

Alternatively (instead of user-info-uri or token-info-uri) if the tokens are JWTs you can configure a spring.oauth2.resource.jwt.key-value to decode them locally (where the key is a verification key). The verification key value is either a symmetric secret or PEM-encoded RSA public key. If you don’t have the key and it’s public you can provide a URI where it can be downloaded (as a JSON object with a “value” field) with spring.oauth2.resource.jwt.key-uri. E.g. on PWS:

$ curl https://uaa.run.pivotal.io/token_key
{"alg":"SHA256withRSA","value":"-----BEGIN PUBLIC KEY-----\nMIIBI...\n-----END PUBLIC KEY-----\n"}
[Warning]Warning

If you use the spring.oauth2.resource.jwt.key-uri the authorization server needs to be running when your application starts up. It will log a warning if it can’t find the key, and tell you what to do to fix it.

28.2 Token Type in User Info

Google, and certain other 3rd party identity providers, are more strict about the token type name that is sent in the headers to the user info endpoint. The default is “Bearer” which suits most providers and matches the spec, but if you need to change it you can set spring.oauth2.resource.token-type.

28.3 Customizing the User Info RestTemplate

If you have a user-info-uri, the resource server features use an OAuth2RestTemplate internally to fetch user details for authentication. This is provided as a qualified @Bean with id userInfoRestTemplate, but you shouldn’t need to know that to just use it. The default should be fine for most providers, but occasionally you might need to add additional interceptors, or change the request authenticator (which is how the token gets attached to outgoing requests). To add a customization just create a bean of type UserInfoRestTemplateCustomizer - it has a single method that will be called after the bean is created but before it is initialized. The rest template that is being customized here is only used internally to carry out authentication.

[Tip]Tip

To set an RSA key value in YAML use the “pipe” continuation marker to split it over multiple lines (“|”) and remember to indent the key value (it’s a standard YAML language feature). Example:

oauth2:
    resource:
        jwt:
            keyValue: |
                -----BEGIN PUBLIC KEY-----
                MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKC...
                -----END PUBLIC KEY-----

28.3.1 Client

To make your webapp into an OAuth2 client you can simply add @EnableOAuth2Client and Spring Boot will create an OAuth2RestTemplate for you to @Autowire. It uses the spring.oauth2.client.* as credentials (the same as you might be using in the Authorization Server), but in addition it will need to know the authorization and token URIs in the Authorization Server. For example:

application.yml. 

spring:
	oauth2:
		client:
			clientId: bd1c0a783ccdd1c9b9e4
			clientSecret: 1a9030fbca47a5b2c28e92f19050bb77824b5ad1
			accessTokenUri: https://github.com/login/oauth/access_token
			userAuthorizationUri: https://github.com/login/oauth/authorize
			clientAuthenticationScheme: form

An application with this configuration will redirect to Github for authorization when you attempt to use the OAuth2RestTemplate. If you are already signed into Github you won’t even notice that it has authenticated. These specific credentials will only work if your application is running on port 8080 (register your own client app in Github or other provider for more flexibility).

To limit the scope that the client asks for when it obtains an access token you can set spring.oauth2.client.scope (comma separated or an array in YAML). By default the scope is empty and it is up to to Authorization Server to decide what the defaults should be, usually depending on the settings in the client registration that it holds.

[Note]Note

There is also a setting for spring.oauth2.client.client-authentication-scheme which defaults to “header” (but you might need to set it to “form” if, like Github for instance, your OAuth2 provider doesn’t like header authentication). In fact, the spring.oauth2.client.* properties are bound to an instance of AuthorizationCodeResourceDetails so all its properties can be specified.

[Tip]Tip

In a non-web application you can still @Autowire an OAuth2RestOperations and it is still wired into the spring.oauth2.client.* configuration. In this case it is a “client credentials token grant” you will be asking for if you use it (and there is no need to use @EnableOAuth2Client or @EnableOAuth2Sso). To switch it off, just remove the spring.oauth2.client.client-id from your configuration (or make it the empty string).

28.3.2 Single Sign On

An OAuth2 Client can be used to fetch user details from the provider (if such features are available) and then convert them into an Authentication token for Spring Security. The Resource Server above support this via the user-info-uri property This is the basis for a Single Sign On (SSO) protocol based on OAuth2, and Spring Boot makes it easy to participate by providing an annotation @EnableOAuth2Sso. The Github client above can protect all its resources and authenticate using the Github /user/ endpoint, by adding that annotation and declaring where to find the endpoint (in addition to the spring.oauth2.client.* configuration already listed above):

application.yml. 

spring:
    oauth2:
...
    resource:
        userInfoUri: https://api.github.com/user
        preferTokenInfo: false

Since all paths are secure by default, there is no “home” page that you can show to unauthenticated users and invite them to login (by visiting the /login path, or the path specified by spring.oauth2.sso.login-path).

To customize the access rules or paths to protect, so you can add a “home” page for instance, @EnableOAuth2Sso can be added to a WebSecurityConfigurerAdapter and the annotation will cause it to be decorated and enhanced with the necessary pieces to get the /login path working. For example, here we simply allow unauthenticated access to the home page at "/" and keep the default for everything else:

@Configuration
public class WebSecurityConfiguration extends WebSecurityConfigurerAdapter {

    @Override
    public void init(WebSecurity web) {
        web.ignore("/");
    }

    @Override
    protected void configure(HttpSecurity http) throws Exception {
        http.antMatcher("/**").authorizeRequests().anyRequest().authenticated();
    }

}

28.4 Actuator Security

If the Actuator is also in use, you will find:

  • The management endpoints are secure even if the application endpoints are unsecure.
  • Security events are transformed into AuditEvents and published to the AuditService.
  • The default user will have the ADMIN role as well as the USER role.

The Actuator security features can be modified using external properties (management.security.*). To override the application access rules add a @Bean of type WebSecurityConfigurerAdapter and use @Order(SecurityProperties.ACCESS_OVERRIDE_ORDER) if you don’t want to override the actuator access rules, or @Order(ManagementServerProperties.ACCESS_OVERRIDE_ORDER) if you do want to override the actuator access rules.

29. Working with SQL databases

The Spring Framework provides extensive support for working with SQL databases. From direct JDBC access using JdbcTemplate to complete ‘object relational mapping’ technologies such as Hibernate. Spring Data provides an additional level of functionality, creating Repository implementations directly from interfaces and using conventions to generate queries from your method names.

29.1 Configure a DataSource

Java’s javax.sql.DataSource interface provides a standard method of working with database connections. Traditionally a DataSource uses a URL along with some credentials to establish a database connection.

29.1.1 Embedded Database Support

It’s often convenient to develop applications using an in-memory embedded database. Obviously, in-memory databases do not provide persistent storage; you will need to populate your database when your application starts and be prepared to throw away data when your application ends.

[Tip]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 don’t need to provide any connection URLs, simply include a build dependency to the embedded database that you want to use.

For example, typical POM dependencies would be:

<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]Note

You need a dependency on spring-jdbc for an embedded database to be auto-configured. In this example it’s pulled in transitively via spring-boot-starter-data-jpa.

29.1.2 Connection to a production database

Production database connections can also be auto-configured using a pooling DataSource. Here’s the algorithm for choosing a specific implementation:

  • We prefer the Tomcat pooling DataSource for its performance and concurrency, so if that is available we always choose it.
  • If HikariCP is available we will use it.
  • If Commons DBCP is available we will use it, but we don’t recommend it in production.
  • Lastly, if Commons DBCP2 is available we will use it.

If you use the spring-boot-starter-jdbc or spring-boot-starter-data-jpa ‘starter POMs’ you will automatically get a dependency to tomcat-jdbc.

[Note]Note

Additional connection pools can always be configured manually. If you define your own DataSource bean, auto-configuration will not occur.

DataSource configuration is controlled by external configuration properties in spring.datasource.*. For example, you might declare the following section in application.properties:

spring.datasource.url=jdbc:mysql://localhost/test
spring.datasource.username=dbuser
spring.datasource.password=dbpass
spring.datasource.driver-class-name=com.mysql.jdbc.Driver

See DataSourceProperties for more of the supported options. Note also that you can configure any of the DataSource implementation specific properties via spring.datasource.*: refer to the documentation of the connection pool implementation you are using for more details.

[Tip]Tip

You often won’t need to specify the driver-class-name since Spring boot can deduce it for most databases from the url.

[Note]Note

For a pooling DataSource to be created we need to be able to verify that a valid Driver class is available, so we check for that before doing anything. I.e. if you set spring.datasource.driverClassName=com.mysql.jdbc.Driver then that class has to be loadable.

29.1.3 Connection to a JNDI DataSource

If you are deploying your Spring Boot application to an Application Server you might want to configure and manage your DataSource using your Application Servers built-in features and access it 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

29.2 Using JdbcTemplate

Spring’s JdbcTemplate and NamedParameterJdbcTemplate classes are auto-configured and you can @Autowire them directly into your own beans:

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;
    }

    // ...

}

29.3 JPA and ‘Spring Data’

The Java Persistence API is a standard technology that allows you to ‘map’ objects to relational databases. The spring-boot-starter-data-jpa POM provides a quick way to get started. It provides the following key dependencies:

  • Hibernate — One of the most popular JPA implementations.
  • Spring Data JPA — Makes it easy to implement JPA-based repositories.
  • Spring ORMs — Core ORM support from the Spring Framework.
[Tip]Tip

We won’t 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.

29.3.1 Entity Classes

Traditionally, JPA ‘Entity’ classes are specified in a persistence.xml file. With Spring Boot this file is not necessary and instead ‘Entity Scanning’ is used. By default all packages below your main configuration class (the one annotated with @EnableAutoConfiguration or @SpringBootApplication) will be searched.

Any classes annotated with @Entity, @Embeddable or @MappedSuperclass will be considered. A typical entity class would look something like this:

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.country = country;
    }

    public String getName() {
        return this.name;
    }

    public String getState() {
        return this.state;
    }

    // ... etc

}
[Tip]Tip

You can customize entity scanning locations using the @EntityScan annotation. See the Section 71.4, “Separate @Entity definitions from Spring configuration” how-to.

29.3.2 Spring Data JPA Repositories

Spring Data JPA repositories are interfaces that you can define to access data. JPA queries are created automatically from your method names. For example, a CityRepository interface might declare a findAllByState(String state) method to find all cities in a given state.

For more complex queries you can annotate your method using Spring Data’s Query annotation.

Spring Data repositories usually extend from the Repository or CrudRepository interfaces. If you are using auto-configuration, repositories will be searched from the package containing your main configuration class (the one annotated with @EnableAutoConfiguration or @SpringBootApplication) down.

Here is a typical Spring Data repository:

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 findByNameAndCountryAllIgnoringCase(String name, String country);

}
[Tip]Tip

We have barely scratched the surface of Spring Data JPA. For complete details check their reference documentation.

29.3.3 Creating and dropping JPA databases

By default, JPA databases will be automatically created only if you use an embedded database (H2, HSQL or Derby). You can explicitly configure JPA settings using spring.jpa.* properties. For example, to create and drop tables you can add the following to your application.properties.

spring.jpa.hibernate.ddl-auto=create-drop
[Note]Note

Hibernate’s own internal property name for this (if you happen to remember it better) is hibernate.hbm2ddl.auto. You can set it, along with other Hibernate native properties, using spring.jpa.properties.* (the prefix is stripped before adding them to the entity manager). Example:

spring.jpa.properties.hibernate.globally_quoted_identifiers=true

passes hibernate.globally_quoted_identifiers 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 autoconfig is active because the ddl-auto settings are more fine-grained.

30. Using jOOQ

Java 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.

30.1 Code Generation

In oder 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 are using 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 (e.g. h2.version) to declare the plugin’s database dependency. Here’s 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>

30.2 Using DSLContext

The fluent API offered by jOOQ is initiated via the org.jooq.DSLContext interface. Spring Boot will auto-configure a DSLContext as a Spring Bean and connect it to your application DataSource. To use the DSLContext you can just @Autowire it:

@Component
public class JooqExample implements CommandLineRunner {

    private final DSLContext create;

    @Autowired
    public JooqExample(DSLContext dlsContext) {
        this.create = dlsContext;
    }

}
[Tip]Tip

The jOOQ manual tends to use a variable named create to hold the DSLContext, we’ve done the same for this example.

You can then use the DSLContext to construct your queries:

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);
}

30.3 Customizing jOOQ

You can customize the SQL dialect used by jOOQ by setting spring.jooq.sql-dialect in your application.properties. For example, to specify Postgres you would add:

spring.jooq.sql-dialect=Postgres

More advanced customizations can be achieved by defining your own @Bean definitions which will be used when the jOOQ Configuration is created. You can define beans for the following jOOQ Types:

  • ConnectionProvider
  • TransactionProvider
  • RecordMapperProvider
  • RecordListenerProvider
  • ExecuteListenerProvider
  • VisitListenerProvider

You can also create your own org.jooq.Configuration @Bean if you want to take complete control of the jOOQ configuration.

31. Working with NoSQL technologies

Spring Data provides additional projects that help you access a variety of NoSQL technologies including MongoDB, Neo4J, Elasticsearch, Solr, Redis, Gemfire, Couchbase and Cassandra. Spring Boot provides auto-configuration for Redis, MongoDB, Elasticsearch, and Solr; you can make use of the other projects, but you will need to configure them yourself. Refer to the appropriate reference documentation at projects.spring.io/spring-data.

31.1 Redis

Redis is a cache, message broker and richly-featured key-value store. Spring Boot offers basic auto-configuration for the Jedis client library and abstractions on top of it provided by Spring Data Redis. There is a spring-boot-starter-redis ‘Starter POM’ for collecting the dependencies in a convenient way.

31.1.1 Connecting to Redis

You can inject an auto-configured RedisConnectionFactory, StringRedisTemplate or vanilla RedisTemplate instance as you would any other Spring Bean. By default the instance will attempt to connect to a Redis server using localhost:6379:

@Component
public class MyBean {

    private StringRedisTemplate template;

    @Autowired
    public MyBean(StringRedisTemplate template) {
        this.template = template;
    }

    // ...

}

If you add a @Bean of your own of any of the auto-configured types it will replace the default (except in the case of RedisTemplate the exclusion is based on the bean name ‘redisTemplate’ not its type). If commons-pool2 is on the classpath you will get a pooled connection factory by default.

31.2 MongoDB

MongoDB is an open-source NoSQL document database that uses a JSON-like schema instead of traditional table-based relational data. Spring Boot offers several conveniences for working with MongoDB, including the spring-boot-starter-data-mongodb ‘Starter POM’.

31.2.1 Connecting to a MongoDB database

You can inject an auto-configured org.springframework.data.mongodb.MongoDbFactory to access Mongo databases. By default the instance will attempt to connect to a MongoDB server using the URL mongodb://localhost/test:

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 spring.data.mongodb.uri property to change the url, or alternatively specify a host/port. For example, you might declare the following in your application.properties:

spring.data.mongodb.host=mongoserver
spring.data.mongodb.port=27017
[Tip]Tip

If spring.data.mongodb.port is not specified the default of 27017 is used. You could simply delete this line from the sample above.

[Tip]Tip

If you aren’t using Spring Data Mongo you can inject com.mongodb.Mongo beans instead of using MongoDbFactory.

You can also declare your own MongoDbFactory or Mongo bean if you want to take complete control of establishing the MongoDB connection.

31.2.2 MongoTemplate

Spring Data Mongo 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 simply inject:

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.

31.2.3 Spring Data MongoDB repositories

Spring Data includes repository support for MongoDB. As with the JPA repositories discussed earlier, the basic principle is that queries are constructed for you automatically based on method names.

In fact, both Spring Data JPA and Spring Data MongoDB share the same common infrastructure; so you could take the JPA example from earlier and, assuming that City is now a Mongo data class rather than a JPA @Entity, it will work in the same way.

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 findByNameAndCountryAllIgnoringCase(String name, String country);

}
[Tip]Tip

For complete details of Spring Data MongoDB, including its rich object mapping technologies, refer to their reference documentation.

31.3 Gemfire

Spring Data Gemfire provides convenient Spring-friendly tools for accessing the Pivotal Gemfire data management platform. There is a spring-boot-starter-data-gemfire ‘Starter POM’ for collecting the dependencies in a convenient way. There is currently no auto-configuration support for Gemfire, but you can enable Spring Data Repositories with a single annotation (@EnableGemfireRepositories).

31.4 Solr

Apache Solr is a search engine. Spring Boot offers basic auto-configuration for the Solr client library and abstractions on top of it provided by Spring Data Solr. There is a spring-boot-starter-data-solr ‘Starter POM’ for collecting the dependencies in a convenient way.

31.4.1 Connecting to Solr

You can inject an auto-configured SolrServer instance as you would any other Spring bean. By default the instance will attempt to connect to a server using localhost:8983/solr:

@Component
public class MyBean {

    private SolrServer solr;

    @Autowired
    public MyBean(SolrServer solr) {
        this.solr = solr;
    }

    // ...

}

If you add a @Bean of your own of type SolrServer it will replace the default.

31.4.2 Spring Data Solr repositories

Spring Data includes repository support for Apache Solr. As with the JPA repositories discussed earlier, the basic principle is that queries are constructed for you automatically based on method names.

In fact, both Spring Data JPA and Spring Data Solr share the same common infrastructure; so you could take the JPA example from earlier and, assuming that City is now a @SolrDocument class rather than a JPA @Entity, it will work in the same way.

[Tip]Tip

For complete details of Spring Data Solr, refer to their reference documentation.

31.5 Elasticsearch

Elasticsearch is an open source, distributed, real-time search and analytics engine. Spring Boot offers basic auto-configuration for the Elasticsearch and abstractions on top of it provided by Spring Data Elasticsearch. There is a spring-boot-starter-data-elasticsearch ‘Starter POM’ for collecting the dependencies in a convenient way.

31.5.1 Connecting to Elasticsearch

You can inject an auto-configured ElasticsearchTemplate or Elasticsearch Client instance as you would any other Spring Bean. By default the instance will attempt to connect to a local in-memory server (a NodeClient in Elasticsearch terms), but you can switch to a remote server (i.e. a TransportClient) by setting spring.data.elasticsearch.cluster-nodes to a comma-separated ‘host:port’ list.

@Component
public class MyBean {

    private ElasticsearchTemplate template;

    @Autowired
    public MyBean(ElasticsearchTemplate template) {
        this.template = template;
    }

    // ...

}

If you add a @Bean of your own of type ElasticsearchTemplate it will replace the default.

31.5.2 Spring Data Elasticsearch repositories

Spring Data includes repository support for Elasticsearch. As with the JPA repositories discussed earlier, the basic principle is that queries are constructed for you automatically based on method names.

In fact, both Spring Data JPA and Spring Data Elasticsearch share the same common infrastructure; so you could take the JPA example from earlier and, assuming that City is now an Elasticsearch @Document class rather than a JPA @Entity, it will work in the same way.

[Tip]Tip

For complete details of Spring Data Elasticsearch, refer to their reference documentation.

32. Caching

The Spring Framework provides support for transparently adding caching to an application. At its core, the abstraction applies caching to methods, reducing thus the number of executions based on the information available in the cache. The caching logic is applied transparently, without any interference to the invoker.

[Note]Note

Check the relevant section of the Spring Framework reference for more details.

In a nutshell, adding caching to an operation of your service is as easy as adding the relevant annotation to its method:

import javax.cache.annotation.CacheResult;

import org.springframework.stereotype.Component;

@Component
public class MathService {

    @CacheResult
    public int computePiDecimal(int i) {
        // ...
    }

}
[Note]Note

You can either use the standard JSR-107 (JCache) annotations or Spring’s own caching annotations transparently. We strongly advise you however to not mix and match them.

[Tip]Tip

It is also possible to update or evict data from the cache transparently.

32.1 Supported cache providers

The cache abstraction does not provide an actual store and relies on a abstraction materialized by the org.springframework.cache.Cache and org.springframework.cache.CacheManager interfaces. Spring Boot auto-configures a suitable CacheManager according to the implementation as long as the caching support is enabled via the @EnableCaching annotation.

[Tip]Tip

Use the spring-boot-starter-cache “Starter POM” to quickly add required caching dependencies. If you are adding dependencies manually you should note that certain implementations are only provided by the spring-context-support jar.

Spring Boot tries to detect the following providers (in this order):

It is also possible to force the cache provider to use via the spring.cache.type property.

32.1.1 Generic

Generic caching is used if the context defines at least one org.springframework.cache.Cache bean, a CacheManager wrapping them is configured.

32.1.2 EhCache 2.x

EhCache 2.x is used if a file named ehcache.xml can be found at the root of the classpath. If EhCache 2.x and such file is present it is used to bootstrap the cache manager. An alternate configuration file can be provide a well using:

spring.cache.ehcache.config=classpath:config/another-config.xml

32.1.3 Hazelcast

Hazelcast is used if a hazelcast.xml file can be found in the current working directory, at the root of the classpath or a location specified via the hazelcast.config system property. Spring Boot detects all of these and also allows for explicit location using:

spring.cache.hazelcast.config=classpath:config/my-hazelcast.xml

32.1.4 Infinispan

Infinispan has no default configuration file location so it must be specified explicitly (or the default bootstrap is used).

spring.cache.infinispan.config=infinispan.xml

Caches can be created on startup via the spring.cache.cache-names property. If a custom ConfigurationBuilder bean is defined, it is used to customize them.

32.1.5 JCache

JCache is bootstrapped via the presence of a javax.cache.spi.CachingProvider on the classpath (i.e. a JSR-107 compliant caching library). It might happen than more that 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 with implementation details.

# Only necessary if more than one provider is present
spring.cache.jcache.provider=com.acme.MyCachingProvider
spring.cache.jcache.config=classpath:acme.xml
[Note]Note

Since a cache library may offer both a native implementation and JSR-107 support it is advised to set the spring.cache.type to jcache to force that mode if that’s what you want.

There are several ways to customize the underlying javax.cache.cacheManager:

  • Caches can be created on startup via the 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]Tip

If a standard javax.cache.CacheManager bean is defined, it is wrapped automatically in a org.springframework.cache.CacheManager implementation that the abstraction expects. No further customization is applied on it.

32.1.6 Redis

If Redis is available and configured, the RedisCacheManager is auto-configured. It is also possible to create additional caches on startup using the spring.cache.cache-names property.

32.1.7 Guava

If Guava is present, a GuavaCacheManager is auto-configured. Caches can be created on startup using the spring.cache.cache-names property and customized by one of the following (in this order):

  1. A cache spec defined by spring.cache.guava.spec
  2. A com.google.common.cache.CacheBuilderSpec bean is defined
  3. A com.google.common.cache.CacheBuilder bean is defined

For instance, the following configuration creates a foo and bar caches with a maximum size of 500 and a time to live of 10 minutes

spring.cache.cache-names=foo,bar
spring.cache.guava.spec=maximumSize=500,expireAfterAccess=600s

Besides, if a com.google.common.cache.CacheLoader bean is defined, it is automatically associated to the GuavaCacheManager.

32.1.8 Simple

If none of these options worked out, a simple implementation using ConcurrentHashMap as cache store is configured. This is the default if no caching library is present in your application.

33. Messaging

The Spring Framework provides extensive support for integrating with messaging systems: from simplified use of the JMS API using JmsTemplate to a complete infrastructure to receive messages asynchronously. Spring AMQP provides a similar feature set for the ‘Advanced Message Queuing Protocol’ and Spring Boot also provides auto-configuration options for RabbitTemplate and RabbitMQ. There is also support for STOMP messaging natively in Spring WebSocket and Spring Boot has support for that through starters and a small amount of auto-configuration.

33.1 JMS

The javax.jms.ConnectionFactory interface provides a standard method of creating a javax.jms.Connection for interacting with a JMS broker. Although Spring needs a ConnectionFactory to work with JMS, you generally won’t need to use it directly yourself and you 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.

33.1.1 ActiveMQ support

Spring Boot can also configure a ConnectionFactory when it detects that ActiveMQ is available on the classpath. If the broker is present, an embedded broker is started and configured automatically (as long as no broker URL is specified through configuration).

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

See ActiveMQProperties for more of the supported options.

By default, ActiveMQ creates a destination if it does not exist yet, so destinations are resolved against their provided names.

33.1.2 Artemis support

Apache Artemis was formed in 2015 when HornetQ was donated to the Apache Foundation. All the features listed in the Section 33.1.3, “HornetQ support” section below can be applied to Artemis. Simply replace spring.hornetq.* properties with spring.artemis.* and use spring-boot-starter-artemis instead of spring-boot-starter-hornetq.

[Note]Note

You should not try and use Artemis and HornetQ and the same time.

33.1.3 HornetQ support

Spring Boot can auto-configure a ConnectionFactory when it detects that HornetQ is available on the classpath. If the broker is present, an embedded broker is started and configured automatically (unless the mode property has been explicitly set). The supported modes are: embedded (to make explicit that an embedded broker is required and should lead to an error if the broker is not available in the classpath), and native to connect to a broker using the netty transport protocol. When the latter is configured, Spring Boot configures a ConnectionFactory connecting to a broker running on the local machine with the default settings.

[Note]Note

If you are using spring-boot-starter-hornetq the necessary dependencies to connect to an existing HornetQ instance are provided, as well as the Spring infrastructure to integrate with JMS. Adding org.hornetq:hornetq-jms-server to your application allows you to use the embedded mode.

HornetQ configuration is controlled by external configuration properties in spring.hornetq.*. For example, you might declare the following section in application.properties:

spring.hornetq.mode=native
spring.hornetq.host=192.168.1.210
spring.hornetq.port=9876

When embedding the broker, you can choose if you want to enable persistence, and the list of 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.hornetq.jms.server.config.JMSQueueConfiguration or org.hornetq.jms.server.config.TopicConfiguration, for advanced queue and topic configurations respectively.

See HornetQProperties for more of the supported options.

No JNDI lookup is involved at all and destinations are resolved against their names, either using the ‘name’ attribute in the HornetQ configuration or the names provided through configuration.

33.1.4 Using a JNDI ConnectionFactory

If you are running your application in an Application Server Spring Boot will attempt to locate a JMS ConnectionFactory using JNDI. By default the locations java:/JmsXA and java:/XAConnectionFactory will be checked. You can use the spring.jms.jndi-name property if you need to specify an alternative location:

spring.jms.jndi-name=java:/MyConnectionFactory

33.1.5 Sending a message

Spring’s JmsTemplate is auto-configured and you can autowire it directly into your own beans:

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]Note

JmsMessagingTemplate (new in Spring 4.1) can be injected in a similar manner.

33.1.6 Receiving a message

When the JMS infrastructure is present, any bean can be annotated with @JmsListener to create a listener endpoint. If no JmsListenerContainerFactory has been defined, a default one is configured automatically.

The following component creates a listener endpoint on the someQueue destination:

@Component
public class MyBean {

    @JmsListener(destination = "someQueue")
    public void processMessage(String content) {
        // ...
    }

}

Check the Javadoc of @EnableJms for more details.

34. Sending email

The Spring Framework provides an easy abstraction for sending email using the JavaMailSender interface and Spring Boot provides auto-configuration for it as well as a starter module.

[Tip]Tip

Check the reference documentation for a detailed explanation of how you can use JavaMailSender.

If spring.mail.host and the relevant libraries (as defined by spring-boot-starter-mail) are available, a default JavaMailSender is created if none exists. The sender can be further customized by configuration items from the spring.mail namespace, see the MailProperties for more details.

35. Distributed Transactions with JTA

Spring Boot supports distributed JTA transactions across multiple XA resources 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 will be used to manage transactions. Auto-configured JMS, DataSource and JPA beans will be 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.

35.1 Using an Atomikos transaction manager

Atomikos is a popular open source transaction manager which can be embedded into your Spring Boot application. You can use the spring-boot-starter-jta-atomikos Starter POM to pull in the appropriate Atomikos libraries. Spring Boot will auto-configure Atomikos and ensure that appropriate depends-on settings are applied to your Spring beans for correct startup and shutdown ordering.

By default Atomikos transaction logs will be written to a transaction-logs directory in your application home directory (the directory in which your application jar file resides). You can customize this directory by setting a spring.jta.log-dir property in your application.properties file. Properties starting spring.jta. can also be used to customize the Atomikos UserTransactionServiceImp. See the AtomikosProperties Javadoc for complete details.

[Note]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 spring.jta.transaction-manager-id property with a different value for each instance of your application.

35.2 Using a Bitronix transaction manager

Bitronix is another popular open source JTA transaction manager implementation. You can use the spring-boot-starter-jta-bitronix starter POM to add the appropriate Birtronix dependencies to your project. As with Atomikos, Spring Boot will automatically configure Bitronix and post-process your beans to ensure that startup and shutdown ordering is correct.

By default Bitronix transaction log files (part1.btm and part2.btm) will be written to a transaction-logs directory in your application home directory. You can customize this directory by using the spring.jta.log-dir property. Properties starting spring.jta. are also bound to the bitronix.tm.Configuration bean, allowing for complete customization. See the Bitronix documentation for details.

[Note]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 spring.jta.transaction-manager-id property with a different value for each instance of your application.

35.3 Using a Java EE managed transaction manager

If you are packaging your Spring Boot application as a war or ear file and deploying it to a Java EE application server, you can use your application servers built-in transaction manager. Spring Boot will attempt to auto-configure a transaction manager by looking at common JNDI locations (java:comp/UserTransaction, java:comp/TransactionManager etc). If you are using a transaction service provided by your application server, you will generally also want to ensure that all resources are managed by the server and exposed over JNDI. Spring Boot will attempt 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.

35.4 Mixing XA and non-XA JMS connections

When using JTA, the primary JMS ConnectionFactory bean will be XA aware and participate in distributed transactions. In some situations you might want to process certain JMS messages 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 using the bean alias xaJmsConnectionFactory.

For example:

// 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;

35.5 Supporting an alternative embedded transaction manager

The XAConnectionFactoryWrapper and XADataSourceWrapper interfaces can be used to support alternative embedded transaction managers. The interfaces are responsible for wrapping XAConnectionFactory and XADataSource beans and exposing them as regular ConnectionFactory and DataSource beans which will transparently enroll in the distributed transaction. DataSource and JMS auto-configuration will use JTA variants as long as 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.

36. Spring Integration

Spring Integration provides abstractions over messaging and also other transports such as HTTP, TCP etc. If Spring Integration is available on your classpath it will be initialized through the @EnableIntegration annotation. Message processing statistics will be published over JMX if 'spring-integration-jmx' is also on the classpath. See the IntegrationAutoConfiguration class for more details.

37. Spring Session

Spring Session provides support for managing a user’s session information. If you are writing a web application and Spring Session and Spring Data Redis are both on the classpath, Spring Boot will auto-configure Spring Session through its @EnableRedisHttpSession. Session data will be stored in Redis and the session timeout can be configured using the server.session-timeout property.

38. Monitoring and management over JMX

Java Management Extensions (JMX) provide a standard mechanism to monitor and manage applications. By default Spring Boot will create an MBeanServer with bean id ‘mbeanServer’ and expose any of your beans that are annotated with Spring JMX annotations (@ManagedResource, @ManagedAttribute, @ManagedOperation).

See the JmxAutoConfiguration class for more details.

39. Testing

Spring Boot provides a number of useful tools for testing your application. The spring-boot-starter-test POM provides Spring Test, JUnit, Hamcrest and Mockito dependencies. There are also useful test utilities in the core spring-boot module under the org.springframework.boot.test package.

39.1 Test scope dependencies

If you use the spring-boot-starter-test ‘Starter POM’ (in the test scope), you will find the following provided libraries:

  • Spring Test — integration test support for Spring applications.
  • JUnit — The de-facto standard for unit testing Java applications.
  • Hamcrest — A library of matcher objects (also known as constraints or predicates) allowing assertThat style JUnit assertions.
  • Mockito — A Java mocking framework.

These are common libraries that we generally find useful when writing tests. You are free to add additional test dependencies of your own if these don’t suit your needs.

39.2 Testing Spring applications

One of the major advantages of dependency injection is that it should make your code easier to unit test. You can simply instantiate objects 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 actually involved in the process). It’s 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 just such integration testing. You can declare a dependency directly to org.springframework:spring-test or use the spring-boot-starter-test ‘Starter POM’ 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.

39.3 Testing Spring Boot applications

A Spring Boot application is just 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. One thing to watch out for though is that the external properties, logging and other features of Spring Boot are only installed in the context by default if you use SpringApplication to create it.

Spring Boot provides a @SpringApplicationConfiguration annotation as an alternative to the standard spring-test @ContextConfiguration annotation. If you use @SpringApplicationConfiguration to configure the ApplicationContext used in your tests, it will be created via SpringApplication and you will get the additional Spring Boot features.

For example:

@RunWith(SpringJUnit4ClassRunner.class)
@SpringApplicationConfiguration(classes = SampleDataJpaApplication.class)
public class CityRepositoryIntegrationTests {

    @Autowired
    CityRepository repository;

    // ...

}
[Tip]Tip

The context loader guesses whether you want to test a web application or not (e.g. with MockMVC) by looking for the @WebIntegrationTest or @WebAppConfiguration annotations. (MockMVC and @WebAppConfiguration are part of spring-test).

If you want a web application to start up and listen on its normal port, so you can test it with HTTP (e.g. using RestTemplate), annotate your test class (or one of its superclasses) with @WebIntegrationTest. This can be very useful because it means you can test the full stack of your application, but also inject its components into the test class and use them to assert the internal state of the application after an HTTP interaction. For example:

@RunWith(SpringJUnit4ClassRunner.class)
@SpringApplicationConfiguration(classes = SampleDataJpaApplication.class)
@WebIntegrationTest
public class CityRepositoryIntegrationTests {

    @Autowired
    CityRepository repository;

    RestTemplate restTemplate = new TestRestTemplate();

    // ... interact with the running server

}
[Note]Note

Spring’s test framework will cache application contexts between tests. Therefore, as long as your tests share the same configuration, the time consuming process of starting and stopping the server will only happen once, regardless of the number of tests that actually run.

To change the port you can add environment properties to @WebIntegrationTest as colon- or equals-separated name-value pairs, e.g. @WebIntegrationTest("server.port:9000"). Additionally you can set the server.port and management.port properties to 0 in order to run your integration tests using random ports. For example:

@RunWith(SpringJUnit4ClassRunner.class)
@SpringApplicationConfiguration(classes = MyApplication.class)
@WebIntegrationTest({"server.port=0", "management.port=0"})
public class SomeIntegrationTests {

    // ...

}

See Section 68.5, “Discover the HTTP port at runtime” for a description of how you can discover the actual port that was allocated for the duration of the tests.

39.3.1 Using Spock to test Spring Boot applications

If you wish to use Spock to test a Spring Boot application you should add a dependency on Spock’s spock-spring module to your application’s build. spock-spring integrates Spring’s test framework into Spock.

[Note]Note

The annotations described above can be used with Spock, i.e. you can annotate your Specification with @WebIntegrationTest to suit the needs of your tests.

39.4 Test utilities

A few test utility classes are packaged as part of spring-boot that are generally useful when testing your application.

39.4.1 ConfigFileApplicationContextInitializer

ConfigFileApplicationContextInitializer is an ApplicationContextInitializer that can apply to your tests to load Spring Boot application.properties files. You can use this when you don’t need the full features provided by @SpringApplicationConfiguration.

@ContextConfiguration(classes = Config.class,
    initializers = ConfigFileApplicationContextInitializer.class)

39.4.2 EnvironmentTestUtils

EnvironmentTestUtils allows you to quickly add properties to a ConfigurableEnvironment or ConfigurableApplicationContext. Simply call it with key=value strings:

EnvironmentTestUtils.addEnvironment(env, "org=Spring", "name=Boot");

39.4.3 OutputCapture

OutputCapture is a JUnit Rule that you can use to capture System.out and System.err output. Simply declare the capture as a @Rule then use toString() for assertions:

import org.junit.Rule;
import org.junit.Test;
import org.springframework.boot.test.OutputCapture;

import static org.hamcrest.Matchers.*;
import static org.junit.Assert.*;

public class MyTest {

	@Rule
	public OutputCapture capture = new OutputCapture();

	@Test
	public void testName() throws Exception {
		System.out.println("Hello World!");
		assertThat(capture.toString(), containsString("World"));
	}

}

39.4.4 TestRestTemplate

TestRestTemplate is a convenience subclass of 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 will behave in a test-friendly way: not following redirects (so you can assert the response location), ignoring cookies (so the template is stateless), and not throwing exceptions on server-side errors. It is recommended, but not mandatory, to use Apache HTTP Client (version 4.3.2 or better), and if you have that on your classpath the TestRestTemplate will respond by configuring the client appropriately.

public class MyTest {

	RestTemplate template = new TestRestTemplate();

	@Test
	public void testRequest() throws Exception {
		HttpHeaders headers = template.getForEntity("http://myhost.com", String.class).getHeaders();
		assertThat(headers.getLocation().toString(), containsString("myotherhost"));
	}

}

40. Developing auto-configuration and using conditions

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.

40.1 Understanding auto-configured beans

Under the hood, auto-configuration is implemented with standard @Configuration classes. Additional @Conditional annotations are used to constrain when the auto-configuration should apply. Usually auto-configuration classes use @ConditionalOnClass and @ConditionalOnMissingBean annotations. This ensures that auto-configuration only applies 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 we provide (see the META-INF/spring.factories file).

40.2 Locating auto-configuration candidates

Spring Boot checks for the presence of a META-INF/spring.factories file within your published jar. The file should list your configuration classes under the EnableAutoConfiguration key.

org.springframework.boot.autoconfigure.EnableAutoConfiguration=\
com.mycorp.libx.autoconfigure.LibXAutoConfiguration,\
com.mycorp.libx.autoconfigure.LibXWebAutoConfiguration

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.

40.3 Condition annotations

You almost always want to include one or more @Conditional annotations on your auto-configuration class. The @ConditionalOnMissingBean 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.

40.3.1 Class conditions

The @ConditionalOnClass and @ConditionalOnMissingClass annotations allows configuration to be included based on the presence or absence of specific classes. Due to the fact that annotation metadata is parsed using ASM you can actually 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 using a String value.

40.3.2 Bean conditions

The @ConditionalOnBean and @ConditionalOnMissingBean annotations allow configurations to 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 allows you to limit the ApplicationContext hierarchy that should be considered when searching for beans.

[Note]Note

@Conditional annotations are processed when @Configuration classes are parsed. Auto-configured @Configuration is always parsed last (after any user defined beans), however, if you are using these annotations on regular @Configuration classes, care must be taken not to refer to bean definitions that have not yet been created.

40.3.3 Property conditions

The @ConditionalOnProperty annotation allows configuration to 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 will be matched. You can also create more advanced checks using the havingValue and matchIfMissing attributes.

40.3.4 Resource conditions

The @ConditionalOnResource annotation allows configuration to be included only when a specific resource is present. Resources can be specified using the usual Spring conventions, for example, file:/home/user/test.dat.

40.3.5 Web application conditions

The @ConditionalOnWebApplication and @ConditionalOnNotWebApplication annotations allow configuration to be included depending on whether the application is a 'web application'. A web application is any application that is using a Spring WebApplicationContext, defines a session scope or has a StandardServletEnvironment.

40.3.6 SpEL expression conditions

The @ConditionalOnExpression annotation allows configuration to be included based on the result of a SpEL expression.

41. WebSockets

Spring Boot provides WebSockets auto-configuration for embedded Tomcat (8 and 7), Jetty 9 and Undertow. If you’re deploying a war file to a standalone container, Spring Boot assumes that the container will be responsible for the configuration of its WebSocket support.

Spring Framework provides rich WebSocket support that can be easily accessed via the spring-boot-starter-websocket module.

42. What to read next

If you want to learn more about any of the classes discussed in this section you can check out the Spring Boot API documentation or you can browse the source code directly. If you have specific questions, take a look at the how-to section.

If you are comfortable with Spring Boot’s core features, you can carry on and read about production-ready features.

Part V. Spring Boot Actuator: Production-ready features

Spring Boot includes a number of additional features to help you monitor and manage your application when it’s pushed to production. You can choose to manage and monitor your application using HTTP endpoints, with JMX or even by remote shell (SSH or Telnet). Auditing, health and metrics gathering can be automatically applied to your application.

43. Enabling production-ready features

The spring-boot-actuator module provides all of Spring Boot’s production-ready features. The simplest way to enable the features is to add a dependency to the spring-boot-starter-actuator ‘Starter POM’.

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 declaration:

dependencies {
    compile("org.springframework.boot:spring-boot-starter-actuator")
}

44. Endpoints

Actuator endpoints allow you to monitor and interact with your application. Spring Boot includes a number of built-in endpoints and you can also add your own. For example the health endpoint provides basic application health information.

The way that endpoints are exposed will depend on the type of technology that you choose. Most applications choose HTTP monitoring, where the ID of the endpoint is mapped to a URL. For example, by default, the health endpoint will be mapped to /health.

The following endpoints are available:

IDDescriptionSensitive

autoconfig

Displays an auto-configuration report showing all auto-configuration candidates and the reason why they ‘were’ or ‘were not’ applied.

true

beans

Displays a complete list of all the Spring beans in your application.

true

configprops

Displays a collated list of all @ConfigurationProperties.

true

dump

Performs a thread dump.

true

env

Exposes properties from Spring’s ConfigurableEnvironment.

true

health

Shows application health information (when the application is secure, a simple ‘status’ when accessed over an unauthenticated connection or full message details when authenticated).

false

info

Displays arbitrary application info.

false

logfile

Returns the contents of the logfile (if logging.file or logging.path properties have been set). Only available via MVC.

true

metrics

Shows ‘metrics’ information for the current application.

true

mappings

Displays a collated list of all @RequestMapping paths.

true

shutdown

Allows the application to be gracefully shutdown (not enabled by default).

true

trace

Displays trace information (by default the last few HTTP requests).

true

[Note]Note

Depending on how an endpoint is exposed, the sensitive property may be used as a security hint. For example, sensitive endpoints will require a username/password when they are accessed over HTTP (or simply disabled if web security is not enabled).

44.1 Customizing endpoints

Endpoints can be customized using Spring properties. You can change if an endpoint is enabled, if it is considered sensitive and even its id.

For example, here is an application.properties that changes the sensitivity and id of the beans endpoint and also enables shutdown.

endpoints.beans.id=springbeans
endpoints.beans.sensitive=false
endpoints.shutdown.enabled=true
[Note]Note

The prefix ‟endpoints + . + name” is used to uniquely identify the endpoint that is being configured.

By default, all endpoints except for shutdown are enabled. If you prefer to specifically “opt-in” endpoint enablement you can use the endpoints.enabled property. For example, the following will disable all endpoints except for info:

endpoints.enabled=false
endpoints.info.enabled=true

44.2 Hypermedia for MVC Endpoints

If Spring HATEOAS is on the classpath (e.g. through the spring-boot-starter-hateoas or if you are using Spring Data REST) then the HTTP endpoints from the Actuator are enhanced with hypermedia links, and a "discovery page" is added with links to all the endpoints. The "discovery page" is actually an endpoint itself, so it can be disabled along with the rest of the hypermedia by setting endpoints.links.enabled=false. If it is not explicitly disabled the links endpoint renders a JSON object with a link for each other endpoint, and the default path is the same as the management.contentPath (so "/" by default).

[Note]Note

if there is a static home page ("index.html") in your application and the links endpoint is registered with its default path ("/") then content negotiation will kick in to determine which content is shown to a client that requests the home page (the links will show only if the client accepts application/json).

If the HAL Browser is on the classpath via its webjar (org.webjars:hal-browser), or via the spring-data-hal-browser then the default home page for HTML clients will be the HAL Browser. This is also exposed via an endpoint ("hal") so it can be disabled and have its path explicitly configured like the other endpoints.

44.3 Adding Custom Endpoints

If you add a @Bean of type Endpoint then it will automatically be exposed over JMX and HTTP (if there is an server available). An HTTP endpoints can be customized further by creating a bean of type MvcEndpoint. Your MvcEndpoint is not a @Controller but it can use @RequestMapping (and @Managed*) to expose resources.

[Tip]Tip

If you are doing this as a library feature consider adding a configuration class to /META-INF/spring.factories under the key org.springframework.boot.actuate.autoconfigure.EndpointWebMvcConfiguration. If you do that then the endpoint will move to a child context with all the other MVC endpoints if your users ask for a separate management port or address. A configuration declared this way can be a WebConfigurerAdapter if it wants to add static resources (for instance) to the management endpoints.

44.4 Health information

Health information can be used to check the status of your running application. It is often used by monitoring software to alert someone if a production system goes down. The default information exposed by the health endpoint depends on how it is accessed. For an unauthenticated connection in a secure application a simple ‘status’ message is returned, and for an authenticated connection additional details are also displayed (see Section 45.6, “HTTP health endpoint access restrictions” for HTTP details).

Health information is collected from all HealthIndicator beans defined in your ApplicationContext. Spring Boot includes a number of auto-configured HealthIndicators and you can also write your own.

44.5 Security with HealthIndicators

Information returned by HealthIndicators is often somewhat sensitive in nature. For example, you probably don’t want to publish details of your database server to the world. For this reason, by default, only the health status is exposed over an unauthenticated HTTP connection. If you are happy for complete health information to always be exposed you can set endpoints.health.sensitive to false.

Health responses are also cached to prevent “denial of service” attacks. Use the endpoints.health.time-to-live property if you want to change the default cache period of 1000 milliseconds.

44.5.1 Auto-configured HealthIndicators

The following HealthIndicators are auto-configured by Spring Boot when appropriate:

NameDescription

DiskSpaceHealthIndicator

Checks for low disk space.

DataSourceHealthIndicator

Checks that a connection to DataSource can be obtained.

MongoHealthIndicator

Checks that a Mongo database is up.

RabbitHealthIndicator

Checks that a Rabbit server is up.

RedisHealthIndicator

Checks that a Redis server is up.

SolrHealthIndicator

Checks that a Solr server is up.

44.5.2 Writing custom HealthIndicators

To provide custom health information you can register Spring beans that implement the HealthIndicator interface. You need to provide an implementation of the health() method and return a Health response. The Health response should include a status and can optionally include additional details to be displayed.

import org.springframework.boot.actuate.health.HealthIndicator;
import org.springframework.stereotype.Component;

@Component
public class MyHealth implements HealthIndicator {

    @Override
    public Health health() {
        int errorCode = check(); // perform some specific health check
        if (errorCode != 0) {
            return Health.down().withDetail("Error Code", errorCode).build();
        }
        return Health.up().build();
    }

}

In addition to Spring Boot’s predefined Status types, it is also possible for Health to return a custom Status that represents a new system state. In such cases a custom implementation of the HealthAggregator interface also needs to be provided, or the default implementation has to be configured using the management.health.status.order configuration property.

For example, assuming a new Status with code FATAL is being used in one of your HealthIndicator implementations. To configure the severity order add the following to your application properties:

management.health.status.order=DOWN, OUT_OF_SERVICE, UNKNOWN, UP

You might also want to register custom status mappings with the HealthMvcEndpoint if you access the health endpoint over HTTP. For example you could map FATAL to HttpStatus.SERVICE_UNAVAILABLE.

44.6 Custom application info information

You can customize the data exposed by the info endpoint by setting info.* Spring properties. All Environment properties under the info key will be automatically exposed. For example, you could add the following to your application.properties:

info.app.name=MyService
info.app.description=My awesome service
info.app.version=1.0.0

44.6.1 Automatically expand info properties at build time

Rather than hardcoding some properties that are also specified in your project’s build configuration, you can automatically expand info properties using the existing build configuration instead. This is possible in both Maven and Gradle.

Automatic property expansion using Maven

You can automatically expand info properties from the Maven project using resource filtering. If you use the spring-boot-starter-parent you can then refer to your Maven ‘project properties’ via @..@ placeholders, e.g.

project.artifactId=myproject
project.name=Demo
project.version=X.X.X.X
project.description=Demo project for info endpoint
info.build.artifact=@project.artifactId@
info.build.name=@project.name@
info.build.description=@project.description@
info.build.version=@project.version@
[Note]Note

In the above example we used project.* to set some values to be used as fallbacks if the Maven resource filtering has not been switched on for some reason.

[Tip]Tip

The spring-boot:run maven goal adds src/main/resources directly to the classpath (for hot reloading purposes). This circumvents the resource filtering and this feature. You can use the exec:java goal instead or customize the plugin’s configuration, see the plugin usage page for more details.

If you don’t use the starter parent, in your pom.xml you need (inside the <build/> element):

<resources>
    <resource>
        <directory>src/main/resources</directory>
        <filtering>true</filtering>
    </resource>
</resources>

and (inside <plugins/>):

<plugin>
    <groupId>org.apache.maven.plugins</groupId>
    <artifactId>maven-resources-plugin</artifactId>
    <version>2.6</version>
    <configuration>
        <delimiters>
            <delimiter>@</delimiter>
        </delimiters>
    </configuration>
</plugin>

Automatic property expansion using Gradle

You can automatically expand info properties from the Gradle project by configuring the Java plugin’s processResources task to do so:

processResources {
    expand(project.properties)
}

You can then refer to your Gradle project’s properties via placeholders, e.g.

info.build.name=${name}
info.build.description=${description}
info.build.version=${version}
[Note]Note

Gradle’s expand method uses Groovy’s SimpleTemplateEngine which transforms ${..} tokens. The ${..} style conflicts with Spring’s own property placeholder mechanism. To use Spring property placeholders together with automatic expansion the Spring property placeholders need to be escaped like \${..}.

44.6.2 Git commit information

Another useful feature of the info endpoint is its ability to publish information about the state of your git source code repository when the project was built. If a git.properties file is contained in your jar the git.branch and git.commit properties will be loaded.

For Maven users the spring-boot-starter-parent POM includes a pre-configured plugin to generate a git.properties file. Simply add the following declaration to your POM:

<build>
    <plugins>
        <plugin>
            <groupId>pl.project13.maven</groupId>
            <artifactId>git-commit-id-plugin</artifactId>
        </plugin>
    </plugins>
</build>

A similar gradle-git plugin is also available for Gradle users, although a little more work is required to generate the properties file.

45. Monitoring and management over HTTP

If you are developing a Spring MVC application, Spring Boot Actuator will auto-configure all enabled endpoints to be exposed over HTTP. The default convention is to use the id of the endpoint as the URL path. For example, health is exposed as /health.

45.1 Securing sensitive endpoints

If you add ‘Spring Security’ to your project, all sensitive endpoints exposed over HTTP will be protected. By default ‘basic’ authentication will be used with the username user and a generated password (which is printed on the console when the application starts).

[Tip]Tip

Generated passwords are logged as the application starts. Search for ‘Using default security password’.

You can use Spring properties to change the username and password and to change the security role required to access the endpoints. For example, you might set the following in your application.properties:

security.user.name=admin
security.user.password=secret
management.security.role=SUPERUSER
[Tip]Tip

If you don’t use Spring Security and your HTTP endpoints are exposed publicly, you should carefully consider which endpoints you enable. See Section 44.1, “Customizing endpoints” for details of how you can set endpoints.enabled to false then “opt-in” only specific endpoints.

45.2 Customizing the management server context path

Sometimes it is useful to group all management endpoints under a single path. For example, your application might already use /info for another purpose. You can use the management.context-path property to set a prefix for your management endpoint:

management.context-path=/manage

The application.properties example above will change the endpoint from /{id} to /manage/{id} (e.g. /manage/info).

45.3 Customizing the management server port

Exposing management endpoints using the default HTTP port is a sensible choice for cloud based deployments. If, however, your application runs inside your own data center you may prefer to expose endpoints using a different HTTP port.

The management.port property can be used to change the HTTP port.

management.port=8081

Since your management port is often protected by a firewall, and not exposed to the public you might not need security on the management endpoints, even if your main application is secure. In that case you will have Spring Security on the classpath, and you can disable management security like this:

management.security.enabled=false

(If you don’t have Spring Security on the classpath then there is no need to explicitly disable the management security in this way, and it might even break the application.)

45.4 Customizing the management server address

You can customize the address that the management endpoints are available on by setting the management.address property. This can be useful if you want to listen only on an internal or ops-facing network, or to only listen for connections from localhost.

[Note]Note

You can only listen on a different address if the port is different to the main server port.

Here is an example application.properties that will not allow remote management connections:

management.port=8081
management.address=127.0.0.1

45.5 Disabling HTTP endpoints

If you don’t want to expose endpoints over HTTP you can set the management port to -1:

management.port=-1

45.6 HTTP health endpoint access restrictions

The information exposed by the health endpoint varies depending on whether or not it’s accessed anonymously, and whether or not the enclosing application is secure. By default, when accessed anonymously in a secure application, any details about the server’s health are hidden and the endpoint will simply indicate whether or not the server is up or down. Furthermore, when accessed anonymously, the response is cached for a configurable period to prevent the endpoint being used in a denial of service attack. The endpoints.health.time-to-live property is used to configure the caching period in milliseconds. It defaults to 1000, i.e. one second.

The above-described restrictions can be enhanced, thereby allowing only authenticated users full access to the health endpoint in a secure application. To do so, set endpoints.health.sensitive to true. Here’s a summary of behavior (with default sensitive flag value “false” indicated in bold):

SecureSensitiveUnauthenticatedAuthenticated

false

false

Full content

Full content

false

true

Status only

Full content

true

false

Status only

Full content

true

true

No content

Full content

46. Monitoring and management over JMX

Java Management Extensions (JMX) provide a standard mechanism to monitor and manage applications. By default Spring Boot will expose management endpoints as JMX MBeans under the org.springframework.boot domain.

46.1 Customizing MBean names

The name of the MBean is usually generated from the id of the endpoint. For example the health endpoint is exposed as org.springframework.boot/Endpoint/healthEndpoint.

If your application contains more than one Spring ApplicationContext you may find that names clash. To solve this problem you can set the endpoints.jmx.unique-names property to true so that MBean names are always unique.

You can also customize the JMX domain under which endpoints are exposed. Here is an example application.properties:

endpoints.jmx.domain=myapp
endpoints.jmx.unique-names=true

46.2 Disabling JMX endpoints

If you don’t want to expose endpoints over JMX you can set the endpoints.jmx.enabled property to false:

endpoints.jmx.enabled=false

46.3 Using Jolokia for JMX over HTTP

Jolokia is a JMX-HTTP bridge giving an alternative method of accessing JMX beans. To use Jolokia, simply include a dependency to org.jolokia:jolokia-core. For example, using Maven you would add the following:

<dependency>
    <groupId>org.jolokia</groupId>
    <artifactId>jolokia-core</artifactId>
 </dependency>

Jolokia can then be accessed using /jolokia on your management HTTP server.

46.3.1 Customizing Jolokia

Jolokia has a number of settings that you would traditionally configure using servlet parameters. With Spring Boot you can use your application.properties, simply prefix the parameter with jolokia.config.:

jolokia.config.debug=true

46.3.2 Disabling Jolokia

If you are using Jolokia but you don’t want Spring Boot to configure it, simply set the endpoints.jolokia.enabled property to false:

endpoints.jolokia.enabled=false

47. Monitoring and management using a remote shell

Spring Boot supports an integrated Java shell called ‘CRaSH’. You can use CRaSH to ssh or telnet into your running application. To enable remote shell support, add the following dependency to your project:

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-remote-shell</artifactId>
 </dependency>
[Tip]Tip

If you want to also enable telnet access you will additionally need a dependency on org.crsh:crsh.shell.telnet.

47.1 Connecting to the remote shell

By default the remote shell will listen for connections on port 2000. The default user is user and the default password will be randomly generated and displayed in the log output. If your application is using Spring Security, the shell will use the same configuration by default. If not, a simple authentication will be applied and you should see a message like this:

Using default password for shell access: ec03e16c-4cf4-49ee-b745-7c8255c1dd7e

Linux and OSX users can use ssh to connect to the remote shell, Windows users can download and install PuTTY.

$ ssh -p 2000 user@localhost

user@localhost's password:
  .   ____          _            __ _ _
 /\\ / ___'_ __ _ _(_)_ __  __ _ \ \ \ \
( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \
 \\/  ___)| |_)| | | | | || (_| |  ) ) ) )
  '  |____| .__|_| |_|_| |_\__, | / / / /
 =========|_|==============|___/=/_/_/_/
 :: Spring Boot ::  (v1.3.0.BUILD-SNAPSHOT) on myhost

Type help for a list of commands. Spring Boot provides metrics, beans, autoconfig and endpoint commands.

47.1.1 Remote shell credentials

You can use the shell.auth.simple.user.name and shell.auth.simple.user.password properties to configure custom connection credentials. It is also possible to use a ‘Spring Security’ AuthenticationManager to handle login duties. See the CrshAutoConfiguration and ShellProperties Javadoc for full details.

47.2 Extending the remote shell

The remote shell can be extended in a number of interesting ways.

47.2.1 Remote shell commands

You can write additional shell commands using Groovy or Java (see the CRaSH documentation for details). By default Spring Boot will search for commands in the following locations:

  • classpath*:/commands/**
  • classpath*:/crash/commands/**
[Tip]Tip

You can change the search path by settings a shell.command-path-patterns property.

Here is a simple ‘hello’ command that could be loaded from src/main/resources/commands/hello.groovy

package commands

import org.crsh.cli.Command
import org.crsh.cli.Usage
import org.crsh.command.InvocationContext

class hello {

    @Usage("Say Hello")
    @Command
    def main(InvocationContext context) {
        return "Hello"
    }

}

Spring Boot adds some additional attributes to InvocationContext that you can access from your command:

Attribute NameDescription

spring.boot.version

The version of Spring Boot

spring.version

The version of the core Spring Framework

spring.beanfactory

Access to the Spring BeanFactory

spring.environment

Access to the Spring Environment

47.2.2 Remote shell plugins

In addition to new commands, it is also possible to extend other CRaSH shell features. All Spring Beans that extend org.crsh.plugin.CRaSHPlugin will be automatically registered with the shell.

For more information please refer to the CRaSH reference documentation.

48. Metrics

Spring Boot Actuator includes a metrics service with ‘gauge’ and ‘counter’ support. A ‘gauge’ records a single value; and a ‘counter’ records a delta (an increment or decrement). Spring Boot Actuator also provides a PublicMetrics interface that you can implement to expose metrics that you cannot record via one of those two mechanisms. Look at SystemPublicMetrics for an example.

Metrics for all HTTP requests are automatically recorded, so if you hit the metrics endpoint you should see a response similar to this:

{
    "counter.status.200.root": 20,
    "counter.status.200.metrics": 3,
    "counter.status.200.star-star": 5,
    "counter.status.401.root": 4,
    "gauge.response.star-star": 6,
    "gauge.response.root": 2,
    "gauge.response.metrics": 3,
    "classes": 5808,
    "classes.loaded": 5808,
    "classes.unloaded": 0,
    "heap": 3728384,
    "heap.committed": 986624,
    "heap.init": 262144,
    "heap.used": 52765,
    "mem": 986624,
    "mem.free": 933858,
    "processors": 8,
    "threads": 15,
    "threads.daemon": 11,
    "threads.peak": 15,
    "uptime": 494836,
    "instance.uptime": 489782,
    "datasource.primary.active": 5,
    "datasource.primary.usage": 0.25
}

Here we can see basic memory, heap, class loading, processor and thread pool information along with some HTTP metrics. In this instance the root (‘/’) and /metrics URLs have returned HTTP 200 responses 20 and 3 times respectively. It also appears that the root URL returned HTTP 401 (unauthorized) 4 times. The double asterix (star-star) comes from a request matched by Spring MVC as /** (normally a static resource).

The gauge shows the last response time for a request. So the last request to root took 2ms to respond and the last to /metrics took 3ms.

[Note]Note

In this example we are actually accessing the endpoint over HTTP using the /metrics URL, this explains why metrics appears in the response.

48.1 System metrics

The following system metrics are exposed by Spring Boot:

  • The total system memory in KB (mem)
  • The amount of free memory in KB (mem.free)
  • The number of processors (processors)
  • The system uptime in milliseconds (uptime)
  • The application context uptime in milliseconds (instance.uptime)
  • The average system load (systemload.average)
  • Heap information in KB (heap, heap.committed, heap.init, heap.used)
  • Thread information (threads, thread.peak, thread.daemon)
  • Class load information (classes, classes.loaded, classes.unloaded)
  • Garbage collection information (gc.xxx.count, gc.xxx.time)

48.2 DataSource metrics

The following metrics are exposed for each supported DataSource defined in your application:

  • The number of active connections (datasource.xxx.active)
  • The current usage of the connection pool (datasource.xxx.usage).

All data source metrics share the datasource. prefix. The prefix is further qualified for each data source:

  • If the data source is the primary data source (that is either the only available data source or the one flagged @Primary amongst the existing ones), the prefix is datasource.primary.
  • If the data source bean name ends with DataSource, the prefix is the name of the bean without DataSource (i.e. datasource.batch for batchDataSource).
  • In all other cases, the name of the bean is used.

It is possible to override part or all of those defaults by registering a bean with a customized version of DataSourcePublicMetrics. By default, Spring Boot provides metadata for all supported data sources; you can add additional DataSourcePoolMetadataProvider beans if your favorite data source isn’t supported out of the box. See DataSourcePoolMetadataProvidersConfiguration for examples.

48.3 Cache metrics

The following metrics are exposed for each supported cache defined in your application:

  • The current size of the cache (cache.xxx.size)
  • Hit ratio (cache.xxx.hit.ratio)
  • Miss ratio (cache.xxx.miss.ratio)
[Note]Note

Cache providers do not expose the hit/miss ratio in a consistent way. While some expose an aggregated value (i.e. the hit ratio since the last time the stats were cleared), others expose a temporal value (i.e. the hit ratio of the last second). Check your caching provider documentation for more details.

If two different cache managers happen to define the same cache, the name of the cache is prefixed by the name of the CacheManager bean.

It is possible to override part or all of those defaults by registering a bean with a customized version of CachePublicMetrics. By default, Spring Boot provides cache statistics for EhCache, Hazelcast, Infinispan, JCache and Guava. You can add additional CacheStatisticsProvider beans if your favorite caching library isn’t supported out of the box. See CacheStatisticsAutoConfiguration for examples.

48.4 Tomcat session metrics

If you are using Tomcat as your embedded servlet container, session metrics will automatically be exposed. The httpsessions.active and httpsessions.max keys provide the number of active and maximum sessions.

48.5 Recording your own metrics

To record your own metrics inject a CounterService and/or GaugeService into your bean. The CounterService exposes increment, decrement and reset methods; the GaugeService provides a submit method.

Here is a simple example that counts the number of times that a method is invoked:

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.actuate.metrics.CounterService;
import org.springframework.stereotype.Service;

@Service
public class MyService {

    private final CounterService counterService;

    @Autowired
    public MyService(CounterService counterService) {
        this.counterService = counterService;
    }

    public void exampleMethod() {
        this.counterService.increment("services.system.myservice.invoked");
    }

}
[Tip]Tip

You can use any string as a metric name but you should follow guidelines of your chosen store/graphing technology. Some good guidelines for Graphite are available on Matt Aimonetti’s Blog.

48.6 Adding your own public metrics

To add additional metrics that are computed every time the metrics endpoint is invoked, simply register additional PublicMetrics implementation bean(s). By default, all such beans are gathered by the endpoint. You can easily change that by defining your own MetricsEndpoint.

48.7 Special features with Java 8

The default implementation of GaugeService and CounterService provided by Spring Boot depends on the version of Java that you are using. With Java 8 (or better) the implementation switches to a high-performance version optimized for fast writes, backed by atomic in-memory buffers, rather than by the immutable but relatively expensive Metric<?> type (counters are approximately 5 times faster and gauges approximately twice as fast as the repository-based implementations). The Dropwizard metrics services (see below) are also very efficient even for Java 7 (they have backports of some of the Java 8 concurrency libraries), but they do not record timestamps for metric values. If performance of metric gathering is a concern then it is always advisable to use one of the high-performance options, and also to only read metrics infrequently, so that the writes are buffered locally and only read when needed.

[Note]Note

The old MetricRepository and its InMemoryMetricRepository implementation are not used by default if you are on Java 8 or if you are using Dropwizard metrics.

48.8 Metric writers, exporters and aggregation

Spring Boot provides a couple of implementations of a marker interface called Exporter which can be used to copy metric readings from the in-memory buffers to a place where they can be analyzed and displayed. Indeed, if you provide a @Bean that implements the MetricWriter interface and mark it @ExportMetricWriter, then it will automatically be hooked up to an Exporter and fed metric updates every 5 seconds (configured via spring.metrics.export.delay-millis). In addition, any MetricReader that you define and mark as @ExportMetricReader will have its values exported by the default exporter.

The default exporter is a MetricCopyExporter which tries to optimize itself by not copying values that haven’t changed since it was last called (the optimization can be switched off using a flag spring.metrics.export.send-latest). Note also that the Dropwizard MetricRegistry has no support for timestamps, so the optimization is not available if you are using Dropwizard metrics (all metrics will be copied on every tick).

The default values for the export trigger (delay-millis, includes, excludes and send-latest) can be set as spring.metrics.export.*. Individual values for specific MetricWriters can be set as spring.metrics.export.triggers.<name>.* where <name> is a bean name (or pattern for matching bean names).

48.8.1 Example: Export to Redis

If you provide a @Bean of type RedisMetricRepository and mark it @ExportMetricWriter the metrics are exported to a Redis cache for aggregation. The RedisMetricRepository has two important parameters to configure it for this purpose: prefix and key (passed into its constructor). It is best to use a prefix that is unique to the application instance (e.g. using a random value and maybe the logical name of the application to make it possible to correlate with other instances of the same application). The “key” is used to keep a global index of all metric names, so it should be unique “globally”, whatever that means for your system (e.g. two instances of the same system could share a Redis cache if they have distinct keys).

Example:

@Bean
@ExportMetricWriter
MetricWriter metricWriter(MetricExportProperties export) {
	return new RedisMetricRepository(connectionFactory,
      export.getRedis().getPrefix(), export.getRedis().getKey());
}

application.properties. 

spring.metrics.export.redis.prefix: metrics.mysystem.${spring.application.name:application}.${random.value:0000}
spring.metrics.export.redis.key: keys.metrics.mysystem

The prefix is constructed with the application name and id at the end, so it can easily be used to identify a group of processes with the same logical name later.

[Note]Note

It’s important to set both the key and the prefix. The key is used for all repository operations, and can be shared by multiple repositories. If multiple repositories share a key (like in the case where you need to aggregate across them), then you normally have a read-only “master” repository that has a short, but identifiable, prefix (like “metrics.mysystem”), and many write-only repositories with prefixes that start with the master prefix (like metrics.mysystem.* in the example above). It is efficient to read all the keys from a “master” repository like that, but inefficient to read a subset with a longer prefix (e.g. using one of the writing repositories).

[Tip]Tip

The example above uses MetricExportProperties to inject and extract the key and prefix. This is provided to you as a convenience by Spring Boot, configured with sensible defaults. There is nothing to stop you using your own values as long as they follow the recommendations.

48.8.2 Example: Export to Open TSDB

If you provide a @Bean of type OpenTsdbHttpMetricWriter and mark it @ExportMetricWriter metrics are exported to Open TSDB for aggregation. The OpenTsdbHttpMetricWriter has a url property that you need to set to the Open TSDB “/put” endpoint, e.g. localhost:4242/api/put). It also has a namingStrategy that you can customize or configure to make the metrics match the data structure you need on the server. By default it just passes through the metric name as an Open TSDB metric name, and adds the tags “domain” (with value “org.springframework.metrics”) and “process” (with the value equal to the object hash of the naming strategy). Thus, after running the application and generating some metrics you can inspect the metrics in the TDB UI (localhost:4242 by default).

Example:

curl localhost:4242/api/query?start=1h-ago&m=max:counter.status.200.root
[
	{
		"metric": "counter.status.200.root",
		"tags": {
			"domain": "org.springframework.metrics",
			"process": "b968a76"
		},
		"aggregateTags": [],
		"dps": {
			"1430492872": 2,
			"1430492875": 6
		}
	}
]

48.8.3 Example: Export to Statsd

If you provide a @Bean of type StatsdMetricWriter and mark it @ExportMetricWriter the metrics are exported to a statsd server:

@Value("${spring.application.name:application}.${random.value:0000}")
private String prefix = "metrics";

@Value("${statsd.host:localhost}")
private String host = "localhost";

@Value("${statsd.port:8125}")
private int port;

@Bean
@ExportMetricWriter
MetricWriter metricWriter() {
	return new StatsdMetricWriter(prefix, host, port);
}

48.8.4 Example: Export to JMX

If you provide a @Bean of type JmxMetricWriter marked @ExportMetricWriter the metrics are exported as MBeans to the local server (the MBeanExporter is provided by Spring Boot JMX autoconfiguration as long as it is switched on). Metrics can then be inspected, graphed, alerted etc. using any tool that understands JMX (e.g. JConsole or JVisualVM).

Example:

@Bean
@ExportMetricWriter
MetricWriter metricWriter(MBeanExporter exporter) {
	return new JmxMetricWriter(exporter);
}

Each metric is exported as an individual MBean. The format for the ObjectNames is given by an ObjectNamingStrategy which can be injected into the JmxMetricWriter (the default breaks up the metric name and tags the first two period-separated sections in a way that should make the metrics group nicely in JVisualVM or JConsole).

48.9 Aggregating metrics from multiple sources

There is an AggregateMetricReader that you can use to consolidate metrics from different physical sources. Sources for the same logical metric just need to publish them with a period-separated prefix, and the reader will aggregate (by truncating the metric names, and dropping the prefix). Counters are summed and everything else (i.e. gauges) take their most recent value.

This is very useful if multiple application instances are feeding to a central (e.g. Redis) repository and you want to display the results. Particularly recommended in conjunction with a MetricReaderPublicMetrics for hooking up to the results to the “/metrics” endpoint.

Example:

@Autowired
private MetricExportProperties export;

@Bean
public PublicMetrics metricsAggregate() {
  return new MetricReaderPublicMetrics(aggregatesMetricReader());
}

private MetricReader globalMetricsForAggregation() {
  return new RedisMetricRepository(this.connectionFactory,
      this.export.getRedis().getAggregatePrefix(), this.export.getRedis().getKey());
}

private MetricReader aggregatesMetricReader() {
  AggregateMetricReader repository = new AggregateMetricReader(
      globalMetricsForAggregation());
  return repository;
}
[Note]Note

The example above uses MetricExportProperties to inject and extract the key and prefix. This is provided to you as a convenience by Spring Boot, and the defaults will be sensible. They are set up in MetricExportAutoConfiguration.

[Note]Note

The MetricReaders above are not @Beans and are not marked as @ExportMetricReader because they are just collecting and analyzing data from other repositories, and don’t want to export their values.

48.10 Dropwizard Metrics

A default MetricRegistry Spring bean will be created when you declare a dependency to the io.dropwizard.metrics:metric-core library; you can also register you own @Bean instance if you need customizations. Users of the Dropwizard ‘Metrics’ library will find that Spring Boot metrics are automatically published to com.codahale.metrics.MetricRegistry. Metrics from the MetricRegistry are also automatically exposed via the /metrics endpoint

When Dropwizard metrics are in use, the default CounterService and GaugeService are replaced with a DropwizardMetricServices, which is a wrapper around the MetricRegistry (so you can @Autowired one of those services and use it as normal). You can also create “special” Dropwizard metrics by prefixing your metric names with the appropriate type (i.e. timer.*, histogram.* for gauges, and meter.* for counters).

48.11 Message channel integration

If a MessageChannel bean called metricsChannel exists, then a MetricWriter will be created that writes metrics to that channel. The writer is automatically hooked up to an exporter (as for all writers), so all metric values will appear on the channel, and additional analysis or actions can be taken by subscribers (it’s up to you to provide the channel and any subscribers you need).

49. Auditing

Spring Boot Actuator has a flexible audit framework that will publish events once Spring Security is in play (‘authentication success’, ‘failure’ and ‘access denied’ exceptions by default). This can be very useful for reporting, and also to implement a lock-out policy based on authentication failures.

You can also choose to use the audit services for your own business events. To do that you can either inject the existing AuditEventRepository into your own components and use that directly, or you can simply publish AuditApplicationEvent via the Spring ApplicationEventPublisher (using ApplicationEventPublisherAware).

50. Tracing

Tracing is automatically enabled for all HTTP requests. You can view the trace endpoint and obtain basic information about the last few requests:

[{
    "timestamp": 1394343677415,
    "info": {
      "method": "GET",
      "path": "/trace",
      "headers": {
        "request": {
          "Accept": "text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8",
          "Connection": "keep-alive",
          "Accept-Encoding": "gzip, deflate",
          "User-Agent": "Mozilla/5.0 Gecko/Firefox",
          "Accept-Language": "en-US,en;q=0.5",
          "Cookie": "_ga=GA1.1.827067509.1390890128; ..."
          "Authorization": "Basic ...",
          "Host": "localhost:8080"
        },
        "response": {
          "Strict-Transport-Security": "max-age=31536000 ; includeSubDomains",
          "X-Application-Context": "application:8080",
          "Content-Type": "application/json;charset=UTF-8",
          "status": "200"
        }
      }
    }
  },{
    "timestamp": 1394343684465,
    ...
    }]

50.1 Custom tracing

If you need to trace additional events you can inject a TraceRepository into your Spring beans. The add method accepts a single Map structure that will be converted to JSON and logged.

By default an InMemoryTraceRepository will be used that stores the last 100 events. You can define your own instance of the InMemoryTraceRepository bean if you need to expand the capacity. You can also create your own alternative TraceRepository implementation if needed.

51. Process monitoring

In Spring Boot Actuator you can find a couple of classes to create files that are useful for process monitoring:

  • ApplicationPidFileWriter creates a file containing the application PID (by default in the application directory with the file name application.pid).
  • EmbeddedServerPortFileWriter creates a file (or files) containing the ports of the embedded server (by default in the application directory with the file name application.port).

These writers are not activated by default, but you can enable them in one of the ways described below.

51.1 Extend configuration

In META-INF/spring.factories file you can activate the listener(s) that writes a PID file. Example:

org.springframework.context.ApplicationListener=\
org.springframework.boot.actuate.system.ApplicationPidFileWriter,
org.springframework.boot.actuate.system.EmbeddedServerPortFileWriter

51.2 Programmatically

You can also activate a listener by invoking the SpringApplication.addListeners(…​) method and passing the appropriate Writer object. This method also allows you to customize the file name and path via the Writer constructor.

52. What to read next

If you want to explore some of the concepts discussed in this chapter, you can take a look at the actuator sample applications. You also might want to read about graphing tools such as Graphite.

Otherwise, you can continue on, to read about ‘deployment options’ or jump ahead for some in-depth information about Spring Boot’s build tool plugins.

53. Deploying Spring Boot applications

54. Deploying to the cloud

Spring Boot’s executable jars are ready-made for most popular cloud PaaS (platform-as-a-service) providers. These providers tend to require that you “bring your own container”; they manage application processes (not Java applications specifically), so they need some intermediary layer that adapts your application to the cloud’s notion of a running process.

Two popular cloud providers, Heroku and Cloud Foundry, employ a “buildpack” approach. The buildpack wraps your deployed code in whatever is needed to start your application: it might be a JDK and a call to java, it might be an embedded webserver, or it might be a full-fledged application server. A buildpack is pluggable, but ideally you should be able to get by with as few customizations to it as possible. This reduces the footprint of functionality that is not under your control. It minimizes divergence between development and production environments.

Ideally, your application, like a Spring Boot executable jar, has everything that it needs to run packaged within it.

In this section we’ll look at what it takes to get the simple application that we developed in the “Getting Started” section up and running in the Cloud.

54.1 Cloud Foundry

Cloud Foundry provides default buildpacks that come into play if no other buildpack is specified. The Cloud Foundry Java buildpack has excellent support for Spring applications, including Spring Boot. You can deploy stand-alone executable jar applications, as well as traditional .war packaged applications.

Once you’ve built your application (using, for example, mvn clean package) and installed the cf command line tool, simply deploy your application using the cf push command as follows, substituting the path to your compiled .jar. Be sure to have logged in with your cf command line client before pushing an application.

$ cf push acloudyspringtime -p target/demo-0.0.1-SNAPSHOT.jar

See the cf push documentation for more options. If there is a Cloud Foundry manifest.yml file present in the same directory, it will be consulted.

[Note]Note

Here we are substituting acloudyspringtime for whatever value you give cf as the name of your application.

At this point cf will start uploading your application:

Uploading acloudyspringtime... OK
Preparing to start acloudyspringtime... OK
-----> Downloaded app package (8.9M)
-----> Java Buildpack source: system
-----> Downloading Open JDK 1.7.0_51 from .../x86_64/openjdk-1.7.0_51.tar.gz (1.8s)
       Expanding Open JDK to .java-buildpack/open_jdk (1.2s)
-----> Downloading Spring Auto Reconfiguration from  0.8.7 .../auto-reconfiguration-0.8.7.jar (0.1s)
-----> Uploading droplet (44M)
Checking status of app 'acloudyspringtime'...
  0 of 1 instances running (1 starting)
  ...
  0 of 1 instances running (1 down)
  ...
  0 of 1 instances running (1 starting)
  ...
  1 of 1 instances running (1 running)

App started

Congratulations! The application is now live!

It’s easy to then verify the status of the deployed application:

$ cf apps
Getting applications in ...
OK

name                 requested state   instances   memory   disk   urls
...
acloudyspringtime    started           1/1         512M     1G     acloudyspringtime.cfapps.io
...

Once Cloud Foundry acknowledges that your application has been deployed, you should be able to hit the application at the URI given, in this case acloudyspringtime.cfapps.io/.

54.1.1 Binding to services

By default, metadata about the running application as well as service connection information is exposed to the application as environment variables (for example: $VCAP_SERVICES). This architecture decision is due to Cloud Foundry’s polyglot (any language and platform can be supported as a buildpack) nature; process-scoped environment variables are language agnostic.

Environment variables don’t always make for the easiest API so Spring Boot automatically extracts them and flattens the data into properties that can be accessed through Spring’s Environment abstraction:

@Component
class MyBean implements EnvironmentAware {

    private String instanceId;

    @Override
    public void setEnvironment(Environment environment) {
        this.instanceId = environment.getProperty("vcap.application.instance_id");
    }

    // ...

}

All Cloud Foundry properties are prefixed with vcap. You can use vcap properties to access application information (such as the public URL of the application) and service information (such as database credentials). See VcapApplicationListener Javadoc for complete details.

[Tip]Tip

The Spring Cloud Connectors project is a better fit for tasks such as configuring a DataSource. Spring Boot includes auto-configuration support and a spring-boot-starter-cloud-connectors starter POM.

54.2 Heroku

Heroku is another popular PaaS platform. To customize Heroku builds, you provide a Procfile, which provides the incantation required to deploy an application. Heroku assigns a port for the Java application to use and then ensures that routing to the external URI works.

You must configure your application to listen on the correct port. Here’s the Procfile for our starter REST application:

web: java -Dserver.port=$PORT -jar target/demo-0.0.1-SNAPSHOT.jar

Spring Boot makes -D arguments available as properties accessible from a Spring Environment instance. The server.port configuration property is fed to the embedded Tomcat, Jetty or Undertow instance which then uses it when it starts up. The $PORT environment variable is assigned to us by the Heroku PaaS.

Heroku by default will use Java 1.8. This is fine as long as your Maven or Gradle build is set to use the same version (Maven users can use the java.version property). If you want to use JDK 1.7, create a new file adjacent to your pom.xml and Procfile, called system.properties. In this file add the following:

java.runtime.version=1.7

This should be everything you need. The most common workflow for Heroku deployments is to git push the code to production.

$ git push heroku master

Initializing repository, done.
Counting objects: 95, done.
Delta compression using up to 8 threads.
Compressing objects: 100% (78/78), done.
Writing objects: 100% (95/95), 8.66 MiB | 606.00 KiB/s, done.
Total 95 (delta 31), reused 0 (delta 0)

-----> Java app detected
-----> Installing OpenJDK 1.8... done
-----> Installing Maven 3.3.1... done
-----> Installing settings.xml... done
-----> Executing: mvn -B -DskipTests=true clean install

       [INFO] Scanning for projects...
       Downloading: http://repo.spring.io/...
       Downloaded: http://repo.spring.io/... (818 B at 1.8 KB/sec)
        ....
       Downloaded: http://s3pository.heroku.com/jvm/... (152 KB at 595.3 KB/sec)
       [INFO] Installing /tmp/build_0c35a5d2-a067-4abc-a232-14b1fb7a8229/target/...
       [INFO] Installing /tmp/build_0c35a5d2-a067-4abc-a232-14b1fb7a8229/pom.xml ...
       [INFO] ------------------------------------------------------------------------
       [INFO] BUILD SUCCESS
       [INFO] ------------------------------------------------------------------------
       [INFO] Total time: 59.358s
       [INFO] Finished at: Fri Mar 07 07:28:25 UTC 2014
       [INFO] Final Memory: 20M/493M
       [INFO] ------------------------------------------------------------------------

-----> Discovering process types
       Procfile declares types -> web

-----> Compressing... done, 70.4MB
-----> Launching... done, v6
       http://agile-sierra-1405.herokuapp.com/ deployed to Heroku

To [email protected]:agile-sierra-1405.git
 * [new branch]      master -> master

Your application should now be up and running on Heroku.

54.3 Openshift

Openshift is the RedHat public (and enterprise) PaaS solution. Like Heroku, it works by running scripts triggered by git commits, so you can script the launching of a Spring Boot application in pretty much any way you like as long as the Java runtime is available (which is a standard feature you can ask for at Openshift). To do this you can use the DIY Cartridge and hooks in your repository under .openshift/action_scripts:

The basic model is to:

  1. Ensure Java and your build tool are installed remotely, e.g. using a pre_build hook (Java and Maven are installed by default, Gradle is not)
  2. Use a build hook to build your jar (using Maven or Gradle), e.g.

    #!/bin/bash
    cd $OPENSHIFT_REPO_DIR
    mvn package -s .openshift/settings.xml -DskipTests=true
  3. Add a start hook that calls java -jar …​

    #!/bin/bash
    cd $OPENSHIFT_REPO_DIR
    nohup java -jar target/*.jar --server.port=${OPENSHIFT_DIY_PORT} --server.address=${OPENSHIFT_DIY_IP} &
  4. Use a stop hook (since the start is supposed to return cleanly), e.g.

    #!/bin/bash
    source $OPENSHIFT_CARTRIDGE_SDK_BASH
    PID=$(ps -ef | grep java.*\.jar | grep -v grep | awk '{ print $2 }')
    if [ -z "$PID" ]
    then
        client_result "Application is already stopped"
    else
        kill $PID
    fi
  5. Embed service bindings from environment variables provided by the platform in your application.properties, e.g.

    spring.datasource.url: jdbc:mysql://${OPENSHIFT_MYSQL_DB_HOST}:${OPENSHIFT_MYSQL_DB_PORT}/${OPENSHIFT_APP_NAME}
    spring.datasource.username: ${OPENSHIFT_MYSQL_DB_USERNAME}
    spring.datasource.password: ${OPENSHIFT_MYSQL_DB_PASSWORD}

There’s a blog on running Gradle in Openshift on their website that will get you started with a gradle build to run the app.

54.4 Google App Engine

Google App Engine is tied to the Servlet 2.5 API, so you can’t deploy a Spring Application there without some modifications. See the Servlet 2.5 section of this guide.

55. Installing Spring Boot applications

In additional to running Spring Boot applications using java -jar it is also possible to make fully executable applications for Unix systems (Linux, OSX, FreeBSD etc). This makes it very easy to install and manage Spring Boot applications in common production environments. As long as you are generating ‘fully executable’ jars from your build, and you are not using a custom embeddedLaunchScript, the following techniques can be used.

To create a ‘fully executable’ jar with Maven use the following plugin configuration:

<plugin>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-maven-plugin</artifactId>
    <configuration>
        <executable>true</executable>
    </configuration>
</plugin>

With Gradle, the equivalent configuration would be:

apply plugin: 'spring-boot'

springBoot {
    executable = true
}
[Note]Note

Fully executable jars work by embedding an extra script at the front of the file. Not all tools currently accept this format so you may not always be able to use this technique.

55.1 Unix/Linux services

Spring Boot application can be easily started as Unix/Linux services using either init.d or systemd.

55.1.1 Installation as a init.d service (System V)

The default executable script that can be embedded into Spring Boot jars will act as an init.d script when it is symlinked to /etc/init.d. The standard start, stop, restart and status commands can be used. The script supports the following features:

  • Starts the services as the user that owns the jar file
  • Tracks application PIDs using /var/run/<appname>/<appname>.pid
  • Writes console logs to /var/log/<appname>.log

Assuming that you have a Spring Boot application installed in /var/myapp, to install a Spring Boot application as an init.d service simply create a symlink:

$ sudo ln -s /var/myapp/myapp.jar /etc/init.d/myapp
[Tip]Tip

It is advisable to create a specific user account to run you application. Ensure that you have set the owner of the jar file using chown before installing your service.

Once installed, you can start and stop the service in the usual way. You can also flag the application to start automatically using your standard operating system tools. For example, if you use Debian:

$ update-rc.d myapp defaults <priority>

55.1.2 Installation as a systemd service

Systemd is the successor to init.d scripts, and now being used by many many modern Linux distributions. Although you can continue to use init.d script with systemd, it is also possible to launch Spring Boot applications using systemd ‘service’ scripts.

For example, to run a Spring Boot application installed in var/myapp you can add the following script in /etc/systemd/system/myapp.service:

[Unit]
Description=myapp
After=syslog.target

[Service]
ExecStart=/var/myapp/myapp.jar

[Install]
WantedBy=multi-user.target
[Tip]Tip

Remember to change the Description and ExecStart fields for your application.

55.1.3 Customizing the startup script

The script accepts the following parameters as environment variables, so you can change the default behavior in a script or on the command line:

VariableDescription

MODE

The “mode” of operation. The default depends on the way the jar was built, but will usually be auto (meaning it tries to guess if it is an init script by checking if it is a symlink in a directory called init.d). You can explicitly set it to service so that the stop|start|status|restart commands work, or to run if you just want to run the script in the foreground.

PID_FOLDER

The root name of the pid folder (/var/run by default).

LOG_FOLDER

The name of the folder to put log files in (/var/log by default).

APP_NAME

The name of the app. If the jar is run from a symlink the script guesses the app name, but if it is not a symlink, or you want to explicitly set the app name this can be useful.

JAVA_HOME

The location of the java executable is discovered by using the PATH by default, but you can set it explicitly if there is an executable file at $JAVA_HOME/bin/java.

JARFILE

The explicit location of the jar file, in case the script is being used to launch a jar that it is not actually embedded in.

DEBUG

if not empty will set the -x flag on the shell process, making it easy to see the logic in the script.

[Tip]Tip

With the exception of JARFILE and APP_NAME, the above settings can be placed in a .conf next to the jar. For example the jar /var/myapp/myapp.jar would attempt to source the configuration file /var/myapp/myapp.conf.

56. What to read next

Check out the Cloud Foundry, Heroku and Openshift web sites for more information about the kinds of features that a PaaS can offer. These are just three of the most popular Java PaaS providers, since Spring Boot is so amenable to cloud-based deployment you’re free to consider other providers as well.

The next section goes on to cover the Spring Boot CLI; or you can jump ahead to read about build tool plugins.

Part VI. Spring Boot CLI

The Spring Boot CLI is a command line tool that can be used if you want to quickly develop with Spring. It allows you to run Groovy scripts, which means that you have a familiar Java-like syntax, without so much boilerplate code. You can also bootstrap a new project or write your own command for it.

57. Installing the CLI

The Spring Boot CLI can be installed manually; using GVM (the Groovy Environment Manually) or using Homebrew or MacPorts if you are an OSX user. See Section 10.2, “Installing the Spring Boot CLI” in the “Getting started” section for comprehensive installation instructions.

58. Using the CLI

Once you have installed the CLI you can run it by typing spring. If you run spring without any arguments, a simple help screen is displayed:

$ spring
usage: spring [--help] [--version]
       <command> [<args>]

Available commands are:

  run [options] <files> [--] [args]
    Run a spring groovy script

  ... more command help is shown here

You can use help to get more details about any of the supported commands. For example:

$ spring help run
spring run - Run a spring groovy script

usage: spring run [options] <files> [--] [args]

Option                     Description
------                     -----------
--autoconfigure [Boolean]  Add autoconfigure compiler
                             transformations (default: true)
--classpath, -cp           Additional classpath entries
-e, --edit                 Open the file with the default system
                             editor
--no-guess-dependencies    Do not attempt to guess dependencies
--no-guess-imports         Do not attempt to guess imports
-q, --quiet                Quiet logging
-v, --verbose              Verbose logging of dependency
                             resolution
--watch                    Watch the specified file for changes

The version command provides a quick way to check which version of Spring Boot you are using.

$ spring version
Spring CLI v1.3.0.BUILD-SNAPSHOT

58.1 Running applications using the CLI

You can compile and run Groovy source code using the run command. The Spring Boot CLI is completely self-contained so you don’t need any external Groovy installation.

Here is an example “hello world” web application written in Groovy:

hello.groovy. 

@RestController
class WebApplication {

    @RequestMapping("/")
    String home() {
        "Hello World!"
    }

}

To compile and run the application type:

$ spring run hello.groovy

To pass command line arguments to the application, you need to use a -- to separate them from the “spring” command arguments, e.g.

$ spring run hello.groovy -- --server.port=9000

To set JVM command line arguments you can use the JAVA_OPTS environment variable, e.g.

$ JAVA_OPTS=-Xmx1024m spring run hello.groovy

58.1.1 Deduced “grab” dependencies

Standard Groovy includes a @Grab annotation which allows you to declare dependencies on a third-party libraries. This useful technique allows Groovy to download jars in the same way as Maven or Gradle would, but without requiring you to use a build tool.

Spring Boot extends this technique further, and will attempt to deduce which libraries to “grab” based on your code. For example, since the WebApplication code above uses @RestController annotations, “Tomcat” and “Spring MVC” will be grabbed.

The following items are used as “grab hints”:

ItemsGrabs

JdbcTemplate, NamedParameterJdbcTemplate, DataSource

JDBC Application.

@EnableJms

JMS Application.

@EnableCaching

Caching abstraction.

@Test

JUnit.

@EnableRabbit

RabbitMQ.

@EnableReactor

Project Reactor.

extends Specification

Spock test.

@EnableBatchProcessing

Spring Batch.

@MessageEndpoint @EnableIntegrationPatterns

Spring Integration.

@EnableDeviceResolver

Spring Mobile.

@Controller @RestController @EnableWebMvc

Spring MVC + Embedded Tomcat.

@EnableWebSecurity

Spring Security.

@EnableTransactionManagement

Spring Transaction Management.

[Tip]Tip

See subclasses of CompilerAutoConfiguration in the Spring Boot CLI source code to understand exactly how customizations are applied.

58.1.2 Deduced “grab” coordinates

Spring Boot extends Groovy’s standard @Grab support by allowing you to specify a dependency without a group or version, for example @Grab('freemarker'). This will consult Spring Boot’s default dependency metadata to deduce the artifact’s group and version. Note that the default metadata is tied to the version of the CLI that you’re using – it will only change when you move to a new version of the CLI, putting you in control of when the versions of your dependencies may change. A table showing the dependencies and their versions that are included in the default metadata can be found in the appendix.

58.1.3 Default import statements

To help reduce the size of your Groovy code, several import statements are automatically included. Notice how the example above refers to @Component, @RestController and @RequestMapping without needing to use fully-qualified names or import statements.

[Tip]Tip

Many Spring annotations will work without using import statements. Try running your application to see what fails before adding imports.

58.1.4 Automatic main method

Unlike the equivalent Java application, you do not need to include a public static void main(String[] args) method with your Groovy scripts. A SpringApplication is automatically created, with your compiled code acting as the source.

58.1.5 Custom dependency management

By default, the CLI uses the dependency management declared in spring-boot-dependencies when resolving @Grab dependencies. Additional dependency management, that will override the default dependency management, can be configured using the @DependencyManagementBom annotation. The annotation’s value should specify the coordinates (groupId:artifactId:version) of one or more Maven boms.

For example, the following declaration:

`@DependencyManagementBom("com.example.custom-bom:1.0.0")`

Will pick up custom-bom-1.0.0.pom in a Maven repository under com/example/custom-versions/1.0.0/.

When multiple boms are specified they are applied in the order that they’re declared. For example:

`@DependencyManagementBom(["com.example.custom-bom:1.0.0",
        "com.example.another-bom:1.0.0"])`

indicates that dependency management in another-bom will override the dependency management in custom-bom.

You can use @DependencyManagementBom anywhere that you can use @Grab, however, to ensure consistent ordering of the dependency management, you can only use @DependencyManagementBom at most once in your application. A useful source of dependency management (that is a superset of Spring Boot’s dependency management) is the Spring IO Platform, e.g. @DepenedencyManagementBom('io.spring.platform:platform-bom:1.1.2.RELEASE').

58.2 Testing your code

The test command allows you to compile and run tests for your application. Typical usage looks like this:

$ spring test app.groovy tests.groovy
Total: 1, Success: 1, : Failures: 0
Passed? true

In this example, tests.groovy contains JUnit @Test methods or Spock Specification classes. All the common framework annotations and static methods should be available to you without having to import them.

Here is the tests.groovy file that we used above (with a JUnit test):

class ApplicationTests {

    @Test
    void homeSaysHello() {
        assertEquals("Hello World!", new WebApplication().home())
    }

}
[Tip]Tip

If you have more than one test source files, you might prefer to organize them into a test directory.

58.3 Applications with multiple source files

You can use “shell globbing” with all commands that accept file input. This allows you to easily use multiple files from a single directory, e.g.

$ spring run *.groovy

This technique can also be useful if you want to segregate your “test” or “spec” code from the main application code:

$ spring test app/*.groovy test/*.groovy

58.4 Packaging your application

You can use the jar command to package your application into a self-contained executable jar file. For example:

$ spring jar my-app.jar *.groovy

The resulting jar will contain the classes produced by compiling the application and all of the application’s dependencies so that it can then be run using java -jar. The jar file will also contain entries from the application’s classpath. You can add explicit paths to the jar using --include and --exclude (both are comma-separated, and both accept prefixes to the values “+” and “-” to signify that they should be removed from the defaults). The default includes are

public/**, resources/**, static/**, templates/**, META-INF/**, *

and the default excludes are

.*, repository/**, build/**, target/**, **/*.jar, **/*.groovy

See the output of spring help jar for more information.

58.5 Initialize a new project

The init command allows you to create a new project using start.spring.io without leaving the shell. For example:

$ spring init --dependencies=web,data-jpa my-project
Using service at https://start.spring.io
Project extracted to '/Users/developer/example/my-project'

This creates a my-project directory with a Maven-based project using spring-boot-starter-web and spring-boot-starter-data-jpa. You can list the capabilities of the service using the --list flag

$ spring init --list
=======================================
Capabilities of https://start.spring.io
=======================================

Available dependencies:
-----------------------
actuator - Actuator: Production ready features to help you monitor and manage your application
...
web - Web: Support for full-stack web development, including Tomcat and spring-webmvc
websocket - Websocket: Support for WebSocket development
ws - WS: Support for Spring Web Services

Available project types:
------------------------
gradle-build -  Gradle Config [format:build, build:gradle]
gradle-project -  Gradle Project [format:project, build:gradle]
maven-build -  Maven POM [format:build, build:maven]
maven-project -  Maven Project [format:project, build:maven] (default)

...

The init command supports many options, check the help output for more details. For instance, the following command creates a gradle project using Java 8 and war packaging:

$ spring init --build=gradle --java-version=1.8 --dependencies=websocket --packaging=war sample-app.zip
Using service at https://start.spring.io
Content saved to 'sample-app.zip'

58.6 Using the embedded shell

Spring Boot includes command-line completion scripts for BASH and zsh shells. If you don’t use either of these shells (perhaps you are a Windows user) then you can use the shell command to launch an integrated shell.

$ spring shell
Spring Boot (v1.3.0.BUILD-SNAPSHOT)
Hit TAB to complete. Type \'help' and hit RETURN for help, and \'exit' to quit.

From inside the embedded shell you can run other commands directly:

$ version
Spring CLI v1.3.0.BUILD-SNAPSHOT

The embedded shell supports ANSI color output as well as tab completion. If you need to run a native command you can use the $ prefix. Hitting ctrl-c will exit the embedded shell.

58.7 Adding extensions to the CLI

You can add extensions to the CLI using the install command. The command takes one or more sets of artifact coordinates in the format group:artifact:version. For example:

$ spring install com.example:spring-boot-cli-extension:1.0.0.RELEASE

In addition to installing the artifacts identified by the coordinates you supply, all of the artifacts' dependencies will also be installed.

To uninstall a dependency use the uninstall command. As with the install command, it takes one or more sets of artifact coordinates in the format group:artifact:version. For example:

$ spring uninstall com.example:spring-boot-cli-extension:1.0.0.RELEASE

It will uninstall the artifacts identified by the coordinates you supply and their dependencies.

To uninstall all additional dependencies you can use the --all option. For example:

$ spring uninstall --all

59. Developing application with the Groovy beans DSL

Spring Framework 4.0 has native support for a beans{} “DSL” (borrowed from Grails), and you can embed bean definitions in your Groovy application scripts using the same format. This is sometimes a good way to include external features like middleware declarations. For example:

@Configuration
class Application implements CommandLineRunner {

    @Autowired
    SharedService service

    @Override
    void run(String... args) {
        println service.message
    }

}

import my.company.SharedService

beans {
    service(SharedService) {
        message = "Hello World"
    }
}

You can mix class declarations with beans{} in the same file as long as they stay at the top level, or you can put the beans DSL in a separate file if you prefer.

60. What to read next

There are some sample groovy scripts available from the GitHub repository that you can use to try out the Spring Boot CLI. There is also extensive javadoc throughout the source code.

If you find that you reach the limit of the CLI tool, you will probably want to look at converting your application to full Gradle or Maven built “groovy project”. The next section covers Spring Boot’s Build tool plugins that you can use with Gradle or Maven.

Part VII. Build tool plugins

Spring Boot provides build tool plugins for Maven and Gradle. The plugins offer a variety of features, including the packaging of executable jars. This section provides more details on both plugins, as well as some help should you need to extend an unsupported build system. If you are just getting started, you might want to read “Chapter 13, Build systems” from the Part III, “Using Spring Boot” section first.

61. Spring Boot Maven plugin

The Spring Boot Maven Plugin provides Spring Boot support in Maven, allowing you to package executable jar or war archives and run an application “in-place”. To use it you must be using Maven 3.2 (or better).

[Note]Note

Refer to the Spring Boot Maven Plugin Site for complete plugin documentation.

61.1 Including the plugin

To use the Spring Boot Maven Plugin simply include the appropriate XML in the plugins section of your pom.xml

<?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 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <!-- ... -->
    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
                <version>1.3.0.BUILD-SNAPSHOT</version>
                <executions>
                    <execution>
                        <goals>
                            <goal>repackage</goal>
                        </goals>
                    </execution>
                </executions>
            </plugin>
        </plugins>
    </build>
</project>

This configuration will repackage a jar or war that is built during the package phase of the Maven lifecycle. The following example shows both the repackaged jar, as well as the original jar, in the target directory:

$ mvn package
$ ls target/*.jar
target/myproject-1.0.0.jar target/myproject-1.0.0.jar.original

If you don’t include the <execution/> configuration as above, you can run the plugin on its own (but only if the package goal is used as well). For example:

$ mvn package spring-boot:repackage
$ ls target/*.jar
target/myproject-1.0.0.jar target/myproject-1.0.0.jar.original

If you are using a milestone or snapshot release you will also need to add appropriate pluginRepository elements:

<pluginRepositories>
    <pluginRepository>
        <id>spring-snapshots</id>
        <url>http://repo.spring.io/snapshot</url>
    </pluginRepository>
    <pluginRepository>
        <id>spring-milestones</id>
        <url>http://repo.spring.io/milestone</url>
    </pluginRepository>
</pluginRepositories>

61.2 Packaging executable jar and war files

Once spring-boot-maven-plugin has been included in your pom.xml it will automatically attempt to rewrite archives to make them executable using the spring-boot:repackage goal. You should configure your project to build a jar or war (as appropriate) using the usual packaging element:

<?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 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <!-- ... -->
    <packaging>jar</packaging>
    <!-- ... -->
</project>

Your existing archive will be enhanced by Spring Boot during the package phase. The main class that you want to launch can either be specified using a configuration option, or by adding a Main-Class attribute to the manifest in the usual way. If you don’t specify a main class the plugin will search for a class with a public static void main(String[] args) method.

To build and run a project artifact, you can type the following:

$ mvn package
$ java -jar target/mymodule-0.0.1-SNAPSHOT.jar

To build a war file that is both executable and deployable into an external container you need to mark the embedded container dependencies as “provided”, e.g:

<?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 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <!-- ... -->
    <packaging>war</packaging>
    <!-- ... -->
    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-tomcat</artifactId>
            <scope>provided</scope>
        </dependency>
        <!-- ... -->
    </dependencies>
</project>
[Tip]Tip

See the “Section 78.1, “Create a deployable war file”” section for more details on how to create a deployable war file.

Advanced configuration options and examples are available in the plugin info page.

62. Spring Boot Gradle plugin

The Spring Boot Gradle Plugin provides Spring Boot support in Gradle, allowing you to package executable jar or war archives, run Spring Boot applications and use the dependency management provided by spring-boot-dependencies.

62.1 Including the plugin

To use the Spring Boot Gradle Plugin simply include a buildscript dependency and apply the spring-boot plugin:

buildscript {
    dependencies {
        classpath("org.springframework.boot:spring-boot-gradle-plugin:1.3.0.BUILD-SNAPSHOT")
    }
}
apply plugin: 'spring-boot'

If you are using a milestone or snapshot release you will also need to add appropriate repositories reference:

buildscript {
    repositories {
        maven.url "http://repo.spring.io/snapshot"
        maven.url "http://repo.spring.io/milestone"
    }
    // ...
}

62.2 Dependency management

The spring-boot plugin automatically applies the Dependency Management Plugin and configures in to import the spring-boot-starter-parent bom. This provides a similar dependency management experience to the one that is enjoyed by Maven users. For example, it allows you to omit version numbers when declaring dependencies that are managed in the bom. To make use of this functionality, simply declare dependencies in the usual way, but leave the version number empty:

dependencies {
    compile("org.springframework.boot:spring-boot-starter-web")
    compile("org.thymeleaf:thymeleaf-spring4")
    compile("nz.net.ultraq.thymeleaf:thymeleaf-layout-dialect")
}
[Note]Note

The version of the spring-boot gradle plugin that you declare determines the version of the spring-boot-starter-parent bom that is imported (this ensures that builds are always repeatable). You should always set the version of the spring-boot gradle plugin to the actual Spring Boot version that you wish to use. Details of the versions that are provided can be found in the appendix.

The dependency management plugin will only supply a version where one is not specified. To use a version of an artifact that differs from the one that the plugin would provide, simply specify the version when you declare the dependency as you usually would. For example:

dependencies {
    compile("org.thymeleaf:thymeleaf-spring4:2.1.1.RELEASE")
}

To learn more about the capabilities of the Dependency Management Plugin, please refer to its documentation.

62.3 Packaging executable jar and war files

Once the spring-boot plugin has been applied to your project it will automatically attempt to rewrite archives to make them executable using the bootRepackage task. You should configure your project to build a jar or war (as appropriate) in the usual way.

The main class that you want to launch can either be specified using a configuration option, or by adding a Main-Class attribute to the manifest. If you don’t specify a main class the plugin will search for a class with a public static void main(String[] args) method.

To build and run a project artifact, you can type the following:

$ gradle build
$ java -jar build/libs/mymodule-0.0.1-SNAPSHOT.jar

To build a war file that is both executable and deployable into an external container, you need to mark the embedded container dependencies as belonging to a configuration named “providedRuntime”, e.g:

...
apply plugin: 'war'

war {
    baseName = 'myapp'
    version =  '0.5.0'
}

repositories {
    jcenter()
    maven { url "http://repo.spring.io/libs-snapshot" }
}

configurations {
    providedRuntime
}

dependencies {
    compile("org.springframework.boot:spring-boot-starter-web")
    providedRuntime("org.springframework.boot:spring-boot-starter-tomcat")
    ...
}
[Tip]Tip

See the “Section 78.1, “Create a deployable war file”” section for more details on how to create a deployable war file.

62.4 Running a project in-place

To run a project in place without building a jar first you can use the “bootRun” task:

$ gradle bootRun

By default, running this way makes your static classpath resources (i.e. in src/main/resources by default) reloadable in the live application, which can be helpful at development time. Making static classpath resources reloadable means that bootRun does not use the output of the processResources task, i.e., when invoked using bootRun, your application will use the resources in their unprocessed form.

You can disable the direct use of your static classpath resources. This will mean that the resources are no longer reloadable but the output of the processResources task will be used. To do so, set addResources on the bootRun task to false:

bootRun {
    addResources = false
}

62.5 Spring Boot plugin configuration

The gradle plugin automatically extends your build script DSL with a springBoot element for global configuration of the Boot plugin. Set the appropriate properties as you would with any other Gradle extension (see below for a list of configuration options):

springBoot {
    backupSource = false
}

62.6 Repackage configuration

The plugin adds a bootRepackage task which you can also configure directly, e.g.:

bootRepackage {
    mainClass = 'demo.Application'
}

The following configuration options are available:

NameDescription

enabled

Boolean flag to switch the repackager off (sometimes useful if you want the other Boot features but not this one)

mainClass

The main class that should be run. If not specified the mainClassName project property will be used or, if the no mainClassName id defined the archive will be searched for a suitable class. "Suitable" means a unique class with a well-formed main() method (if more than one is found the build will fail). You should also be able to specify the main class name via the "run" task (main property) and/or the "startScripts" (mainClassName property) as an alternative to using the "springBoot" configuration.

classifier

A file name segment (before the extension) to add to the archive, so that the original is preserved in its original location. Defaults to null in which case the archive is repackaged in place. The default is convenient for many purposes, but if you want to use the original jar as a dependency in another project, it’s best to use an extension to define the executable archive.

withJarTask

The name or value of the Jar task (defaults to all tasks of type Jar) which is used to locate the archive to repackage.

customConfiguration

The name of the custom configuration which is used to populate the nested lib directory (without specifying this you get all compile and runtime dependencies).

executable

Boolean flag to indicate if jar files are fully executable on Unix like operating systems. Defaults to true.

embeddedLaunchScript

The embedded launch script to prepend to the front of the jar if it is fully executable. If not specified the 'Spring Boot' default script will be used.

embeddedLaunchScriptProperties

Additional properties that to be expanded in the launch script. The default script supports a mode property which can contain the values auto, service or run.

62.7 Repackage with custom Gradle configuration

Sometimes it may be more appropriate to not package default dependencies resolved from compile, runtime and provided scopes. If the created executable jar file is intended to be run as it is, you need to have all dependencies nested inside it; however, if the plan is to explode a jar file and run the main class manually, you may already have some of the libraries available via CLASSPATH. This is a situation where you can repackage your jar with a different set of dependencies.

Using a custom configuration will automatically disable dependency resolving from compile, runtime and provided scopes. Custom configuration can be either defined globally (inside the springBoot section) or per task.

task clientJar(type: Jar) {
    appendix = 'client'
    from sourceSets.main.output
    exclude('**/*Something*')
}

task clientBoot(type: BootRepackage, dependsOn: clientJar) {
    withJarTask = clientJar
    customConfiguration = "mycustomconfiguration"
}

In above example, we created a new clientJar Jar task to package a customized file set from your compiled sources. Then we created a new clientBoot BootRepackage task and instructed it to work with only clientJar task and mycustomconfiguration.

configurations {
    mycustomconfiguration.exclude group: 'log4j'
}

dependencies {
    mycustomconfiguration configurations.runtime
}

The configuration that we are referring to in BootRepackage is a normal Gradle configuration. In the above example we created a new configuration named mycustomconfiguration instructing it to derive from a runtime and exclude the log4j group. If the clientBoot task is executed, the repackaged boot jar will have all dependencies from runtime but no log4j jars.

62.7.1 Configuration options

The following configuration options are available:

NameDescription

mainClass

The main class that should be run by the executable archive.

providedConfiguration

The name of the provided configuration (defaults to providedRuntime).

backupSource

If the original source archive should be backed-up before being repackaged (defaults to true).

customConfiguration

The name of the custom configuration.

layout

The type of archive, corresponding to how the dependencies are laid out inside (defaults to a guess based on the archive type).

requiresUnpack

A list of dependencies (in the form “groupId:artifactId” that must be unpacked from fat jars in order to run. Items are still packaged into the fat jar, but they will be automatically unpacked when it runs.

62.8 Understanding how the Gradle plugin works

When spring-boot is applied to your Gradle project a default task named bootRepackage is created automatically. The bootRepackage task depends on Gradle assemble task, and when executed, it tries to find all jar artifacts whose qualifier is empty (i.e. tests and sources jars are automatically skipped).

Due to the fact that bootRepackage finds 'all' created jar artifacts, the order of Gradle task execution is important. Most projects only create a single jar file, so usually this is not an issue; however, if you are planning to create a more complex project setup, with custom Jar and BootRepackage tasks, there are few tweaks to consider.

If you are 'just' creating custom jar files from your project you can simply disable default jar and bootRepackage tasks:

jar.enabled = false
bootRepackage.enabled = false

Another option is to instruct the default bootRepackage task to only work with a default jar task.

bootRepackage.withJarTask = jar

If you have a default project setup where the main jar file is created and repackaged, 'and' you still want to create additional custom jars, you can combine your custom repackage tasks together and use dependsOn so that the bootJars task will run after the default bootRepackage task is executed:

task bootJars
bootJars.dependsOn = [clientBoot1,clientBoot2,clientBoot3]
build.dependsOn(bootJars)

All the above tweaks are usually used to avoid situations where an already created boot jar is repackaged again. Repackaging an existing boot jar will not break anything, but you may find that it includes unnecessary dependencies.

62.9 Publishing artifacts to a Maven repository using Gradle

If you are declaring dependencies without versions and you want to publish artifacts to a Maven repository you will need to configure the Maven publication with details of Spring Boot’s dependency management. This can be achieved by configuring it to publish poms that inherit from spring-boot-starter-parent or that import dependency management from spring-boot-dependencies. The exact details of this configuration depend on how you’re using Gradle and how you’re trying to publish the artifacts.

62.9.1 Configuring Gradle to produce a pom that inherits dependency management

The following is an example of configuring Gradle to generate a pom that inherits from spring-boot-starter-parent. Please refer to the Gradle User Guide for further information.

uploadArchives {
    repositories {
        mavenDeployer {
            pom {
                project {
                    parent {
                        groupId "org.springframework.boot"
                        artifactId "spring-boot-starter-parent"
                        version "1.3.0.BUILD-SNAPSHOT"
                    }
                }
            }
        }
    }
}

62.9.2 Configuring Gradle to produce a pom that imports dependency management

The following is an example of configuring Gradle to generate a pom that imports the dependency management provided by spring-boot-dependencies. Please refer to the Gradle User Guide for further information.

uploadArchives {
    repositories {
        mavenDeployer {
            pom {
                project {
                    dependencyManagement {
                        dependencies {
                            dependency {
                                groupId "org.springframework.boot"
                                artifactId "spring-boot-dependencies"
                                version "1.3.0.BUILD-SNAPSHOT"
                                type "pom"
                                scope "import"
                            }
                        }
                    }
                }
            }
        }
    }
}

63. Spring Boot AntLib module

The Spring Boot AntLib module provides basic Spring Boot support for Apache Ant. You can use the module to create executable jars. To use the module you need to declare an additional spring-boot namespace in your build.xml:

<project xmlns:ivy="antlib:org.apache.ivy.ant"
    xmlns:spring-boot="antlib:org.springframework.boot.ant"
    name="myapp" default="build">
    ...
</project>

You’ll need to remember to start Ant using the -lib option, for example:

$ ant -lib <folder containing spring-boot-antlib-1.3.0.BUILD-SNAPSHOT.jar>
[Tip]Tip

The “Using Spring Boot” section includes a more complete example of using Apache Ant with spring-boot-antlib

63.1 Spring Boot Ant tasks

Once the spring-boot-antlib namespace has been declared, the following additional tasks are available.

63.1.1 spring-boot:exejar

The exejar task can be used to creates a Spring Boot executable jar. The following attributes are supported by the task:

AttributeDescriptionRequired

destfile

The destination jar file to create

Yes

classes

The root directory of Java classfiles

Yes

start-class

The main application class to run

No (default is first class found declaring a main method)

The following nested elements can be used with the task:

ElementDescription

resources

One or more Resource Collections describing a set of Resources that should be added to the content of the created jar file.

lib

One or more Resource Collections that should be added to the set of jar libraries that make up the runtime dependency classpath of the application.

Examples

Specify start-class. 

<spring-boot:exejar destfile="target/my-application.jar"
        classes="target/classes" start-class="com.foo.MyApplication">
    <resources>
        <fileset dir="src/main/resources" />
    </resources>
    <lib>
        <fileset dir="lib" />
    </lib>
</spring-boot:exejar>

Detect start-class. 

<exejar destfile="target/my-application.jar" classes="target/classes">
    <lib>
        <fileset dir="lib" />
    </lib>
</exejar>

63.2 spring-boot:findmainclass

The findmainclass task is used internally by exejar to locate a class declaring a main. You can also use this task directly in your build if needed. The following attributes are supported

AttributeDescriptionRequired

classesroot

The root directory of Java classfiles

Yes (unless mainclass is specified)

mainclass

Can be used to short-circuit the main class search

No

property

The Ant property that should be set with the result

No (result will be logged if unspecified)

63.2.1 Examples

Find and log. 

<findmainclass classesroot="target/classes" />

Find and set. 

<findmainclass classesroot="target/classes" property="main-class" />

Override and set. 

<findmainclass mainclass="com.foo.MainClass" property="main-class" />

64. Supporting other build systems

If you want to use a build tool other than Maven, Gradle or Ant, you will likely need to develop your own plugin. Executable jars need to follow a specific format and certain entries need to be written in an uncompressed form (see the executable jar format section in the appendix for details).

The Spring Boot Maven and Gradle plugins both make use of spring-boot-loader-tools to actually generate jars. You are also free to use this library directly yourself if you need to.

64.1 Repackaging archives

To repackage an existing archive so that it becomes a self-contained executable archive use org.springframework.boot.loader.tools.Repackager. The Repackager class takes a single constructor argument that refers to an existing jar or war archive. Use one of the two available repackage() methods to either replace the original file or write to a new destination. Various settings can also be configured on the repackager before it is run.

64.2 Nested libraries

When repackaging an archive you can include references to dependency files using the org.springframework.boot.loader.tools.Libraries interface. We don’t provide any concrete implementations of Libraries here as they are usually build system specific.

If your archive already includes libraries you can use Libraries.NONE.

64.3 Finding a main class

If you don’t use Repackager.setMainClass() to specify a main class, the repackager will use ASM to read class files and attempt to find a suitable class with a public static void main(String[] args) method. An exception is thrown if more than one candidate is found.

64.4 Example repackage implementation

Here is a typical example repackage:

Repackager repackager = new Repackager(sourceJarFile);
repackager.setBackupSource(false);
repackager.repackage(new Libraries() {
            @Override
            public void doWithLibraries(LibraryCallback callback) throws IOException {
                // Build system specific implementation, callback for each dependency
                // callback.library(new Library(nestedFile, LibraryScope.COMPILE));
            }
        });

65. What to read next

If you’re interested in how the build tool plugins work you can look at the spring-boot-tools module on GitHub. More technical details of the executable jar format are covered in the appendix.

If you have specific build-related questions you can check out the “how-to” guides.

Part VIII. ‘How-to’ guides

This section provides answers to some common ‘how do I do that…​’ type of questions that often arise when using Spring Boot. This is by no means an exhaustive list, but it does cover quite a lot.

If you are having a specific problem that we don’t cover here, you might want to check out stackoverflow.com to see if someone has already provided an answer; this is also a great place to ask new questions (please use the spring-boot tag).

We’re also more than happy to extend this section; If you want to add a ‘how-to’ you can send us a pull request.

66. Spring Boot application

66.1 Troubleshoot auto-configuration

The Spring Boot auto-configuration tries its best to ‘do the right thing’, but sometimes things fail and it can be hard to tell why.

There is a really useful ConditionEvaluationReport available in any Spring Boot ApplicationContext. You will see it if you enable DEBUG logging output. If you use the spring-boot-actuator there is also an autoconfig endpoint that renders the report in JSON. Use that to debug the application and see what features have been added (and which not) by Spring Boot at runtime.

Many more questions can be answered by looking at the source code and the javadoc. Some rules of thumb:

  • Look for classes called *AutoConfiguration and read their sources, in particular the @Conditional* annotations to find out what features they enable and when. Add --debug to the command line or a System property -Ddebug to get a log on the console of all the autoconfiguration decisions that were made in your app. In a running Actuator app look at the autoconfig endpoint (‘/autoconfig’ or the JMX equivalent) for the same information.
  • Look for classes that are @ConfigurationProperties (e.g. ServerProperties) and read from there the available external configuration options. The @ConfigurationProperties has a name attribute which acts as a prefix to external properties, thus ServerProperties has prefix="server" and its configuration properties are server.port, server.address etc. In a running Actuator app look at the configprops endpoint.
  • Look for use of RelaxedEnvironment to pull configuration values explicitly out of the Environment. It often is used with a prefix.
  • Look for @Value annotations that bind directly to the Environment. This is less flexible than the RelaxedEnvironment approach, but does allow some relaxed binding, specifically for OS environment variables (so CAPITALS_AND_UNDERSCORES are synonyms for period.separated).
  • Look for @ConditionalOnExpression annotations that switch features on and off in response to SpEL expressions, normally evaluated with place-holders resolved from the Environment.

66.2 Customize the Environment or ApplicationContext before it starts

A SpringApplication has ApplicationListeners and ApplicationContextInitializers that are used to apply customizations to the context or environment. Spring Boot loads a number of such customizations for use internally from META-INF/spring.factories. There is more than one way to register additional ones:

  • Programmatically per application by calling the addListeners and addInitializers methods on SpringApplication before you run it.
  • Declaratively per application by setting context.initializer.classes or context.listener.classes.
  • Declaratively for all applications by adding a META-INF/spring.factories and packaging a jar file that the applications all use as a library.

The SpringApplication sends some special ApplicationEvents to the listeners (even some before the context is created), and then registers the listeners for events published by the ApplicationContext as well. See Section 23.4, “Application events and listeners” in the ‘Spring Boot features’ section for a complete list.

66.3 Build an ApplicationContext hierarchy (adding a parent or root context)

You can use the ApplicationBuilder class to create parent/child ApplicationContext hierarchies. See Section 23.3, “Fluent builder API” in the ‘Spring Boot features’ section for more information.

66.4 Create a non-web application

Not all Spring applications have to be web applications (or web services). If you want to execute some code in a main method, but also bootstrap a Spring application to set up the infrastructure to use, then it’s easy with the SpringApplication features of Spring Boot. A SpringApplication changes its ApplicationContext class depending on whether it thinks it needs a web application or not. The first thing you can do to help it is to just leave the servlet API dependencies off the classpath. If you can’t do that (e.g. you are running 2 applications from the same code base) then you can explicitly call SpringApplication.setWebEnvironment(false), or set the applicationContextClass property (through the Java API or with external properties). Application code that you want to run as your business logic can be implemented as a CommandLineRunner and dropped into the context as a @Bean definition.

67. Properties & configuration

67.1 Externalize the configuration of SpringApplication

A SpringApplication has bean properties (mainly setters) so you can use its Java API as you create the application to modify its behavior. Or you can externalize the configuration using properties in spring.main.*. E.g. in application.properties you might have.

spring.main.web_environment=false
spring.main.show_banner=false

and then the Spring Boot banner will not be printed on startup, and the application will not be a web application.

[Note]Note

The example above also demonstrates how flexible binding allows the use of underscores (_) as well as dashes (-) in property names.

Properties defined in external configuration overrides the values specified via the Java API with the notable exception of the sources used to create the ApplicationContext. Let’s consider this application

new SpringApplicationBuilder()
    .showBanner(false)
    .sources(demo.MyApp.class)
    .run(args);

used with the following configuration:

spring.main.sources=com.acme.Config,com.acme.ExtraConfig
spring.main.show-banner=true

The actual application will now show the banner (as overridden by configuration) and use three sources for the ApplicationContext (in that order): demo.MyApp, com.acme.Config, com.acme.ExtraConfig.

67.2 Change the location of external properties of an application

By default properties from different sources are added to the Spring Environment in a defined order (see Chapter 24, Externalized Configuration in the ‘Spring Boot features’ section for the exact order).

A nice way to augment and modify this is to add @PropertySource annotations to your application sources. Classes passed to the SpringApplication static convenience methods, and those added using setSources() are inspected to see if they have @PropertySources, and if they do, those properties are added to the Environment early enough to be used in all phases of the ApplicationContext lifecycle. Properties added in this way have precedence over any added using the default locations, but have lower priority than system properties, environment variables or the command line.

You can also provide System properties (or environment variables) to change the behavior:

  • spring.config.name (SPRING_CONFIG_NAME), defaults to application as the root of the file name.
  • spring.config.location (SPRING_CONFIG_LOCATION) is the file to load (e.g. a classpath resource or a URL). A separate Environment property source is set up for this document and it can be overridden by system properties, environment variables or the command line.

No matter what you set in the environment, Spring Boot will always load application.properties as described above. If YAML is used then files with the ‘.yml’ extension are also added to the list by default.

See ConfigFileApplicationListener for more detail.

67.3 Use ‘short’ command line arguments

Some people like to use (for example) --port=9000 instead of --server.port=9000 to set configuration properties on the command line. You can easily enable this by using placeholders in application.properties, e.g.

server.port=${port:8080}
[Tip]Tip

If you are inheriting from the spring-boot-starter-parent POM, the default filter token of the maven-resources-plugins has been changed from ${*} to @ (i.e. @maven.token@ instead of ${maven.token}) to prevent conflicts with Spring-style placeholders. If you have enabled maven filtering for the application.properties directly, you may want to also change the default filter token to use other delimiters.

[Note]Note

In this specific case the port binding will work in a PaaS environment like Heroku and Cloud Foundry, since in those two platforms the PORT environment variable is set automatically and Spring can bind to capitalized synonyms for Environment properties.

67.4 Use YAML for external properties

YAML is a superset of JSON and as such is a very convenient syntax for storing external properties in a hierarchical format. E.g.

spring:
    application:
        name: cruncher
    datasource:
        driverClassName: com.mysql.jdbc.Driver
        url: jdbc:mysql://localhost/test
server:
    port: 9000

Create a file called application.yml and stick it in the root of your classpath, and also add snakeyaml to your dependencies (Maven coordinates org.yaml:snakeyaml, already included if you use the spring-boot-starter). A YAML file is parsed to a Java Map<String,Object> (like a JSON object), and Spring Boot flattens the map so that it is 1-level deep and has period-separated keys, a lot like people are used to with Properties files in Java.

The example YAML above corresponds to an application.properties file

spring.application.name=cruncher
spring.datasource.driverClassName=com.mysql.jdbc.Driver
spring.datasource.url=jdbc:mysql://localhost/test
server.port=9000

See Section 24.6, “Using YAML instead of Properties” in the ‘Spring Boot features’ section for more information about YAML.

67.5 Set the active Spring profiles

The Spring Environment has an API for this, but normally you would set a System profile (spring.profiles.active) or an OS environment variable (SPRING_PROFILES_ACTIVE). E.g. launch your application with a -D argument (remember to put it before the main class or jar archive):

$ java -jar -Dspring.profiles.active=production demo-0.0.1-SNAPSHOT.jar

In Spring Boot you can also set the active profile in application.properties, e.g.

spring.profiles.active=production

A value set this way is replaced by the System property or environment variable setting, but not by the SpringApplicationBuilder.profiles() method. Thus the latter Java API can be used to augment the profiles without changing the defaults.

See Chapter 25, Profiles in the ‘Spring Boot features’ section for more information.

67.6 Change configuration depending on the environment

A YAML file is actually a sequence of documents separated by --- lines, and each document is parsed separately to a flattened map.

If a YAML document contains a spring.profiles key, then the profiles value (comma-separated list of profiles) is fed into the Spring Environment.acceptsProfiles() and if any of those profiles is active that document is included in the final merge (otherwise not).

Example:

server:
    port: 9000
---

spring:
    profiles: development
server:
    port: 9001

---

spring:
    profiles: production
server:
    port: 0

In this example the default port is 9000, but if the Spring profile ‘development’ is active then the port is 9001, and if ‘production’ is active then it is 0.

The YAML documents are merged in the order they are encountered (so later values override earlier ones).

To do the same thing with properties files you can use application-${profile}.properties to specify profile-specific values.

67.7 Discover built-in options for external properties

Spring Boot binds external properties from application.properties (or .yml) (and other places) into an application at runtime. There is not (and technically cannot be) an exhaustive list of all supported properties in a single location because contributions can come from additional jar files on your classpath.

A running application with the Actuator features has a configprops endpoint that shows all the bound and bindable properties available through @ConfigurationProperties.

The appendix includes an application.properties example with a list of the most common properties supported by Spring Boot. The definitive list comes from searching the source code for @ConfigurationProperties and @Value annotations, as well as the occasional use of RelaxedEnvironment.

68. Embedded servlet containers

68.1 Add a Servlet, Filter or ServletContextListener to an application

Servlet, Filter, ServletContextListener and the other listeners supported by the Servlet spec can be added to your application as @Bean definitions. Be very careful that they don’t cause eager initialization of too many other beans because they have to be installed in the container very early in the application lifecycle (e.g. it’s not a good idea to have them depend on your DataSource or JPA configuration). You can work around restrictions like that by initializing them lazily when first used instead of on initialization.

In the case of Filters and Servlets you can also add mappings and init parameters by adding a FilterRegistrationBean or ServletRegistrationBean instead of or as well as the underlying component.

68.2 Disable registration of a Servlet or Filter

As described above any Servlet or Filter beans will be registered with the servlet container automatically. To disable registration of a particular Filter or Servlet bean create a registration bean for it and mark it as disabled. For example:

@Bean
public FilterRegistrationBean registration(MyFilter filter) {
    FilterRegistrationBean registration = new FilterRegistrationBean(filter);
    registration.setEnabled(false);
    return registration;
}

68.3 Change the HTTP port

In a standalone application the main HTTP port defaults to 8080, but can be set with server.port (e.g. in application.properties or as a System property). Thanks to relaxed binding of Environment values you can also use SERVER_PORT (e.g. as an OS environment variable).

To switch off the HTTP endpoints completely, but still create a WebApplicationContext, use server.port=-1 (this is sometimes useful for testing).

For more details look at Section 27.3.3, “Customizing embedded servlet containers” in the ‘Spring Boot features’ section, or the ServerProperties source code.

68.4 Use a random unassigned HTTP port

To scan for a free port (using OS natives to prevent clashes) use server.port=0.

[Tip]Tip

You can know what port got allocated at runtime by looking at the local.server.port property in the Environment.

68.5 Discover the HTTP port at runtime

You can access the port the server is running on from log output or from the EmbeddedWebApplicationContext via its EmbeddedServletContainer. The best way to get that and be sure that it has initialized is to add a @Bean of type ApplicationListener<EmbeddedServletContainerInitializedEvent> and pull the container out of the event when it is published.

A useful practice for use with @WebIntegrationTests is to set server.port=0 and then inject the actual (‘local’) port as a @Value. For example:

@RunWith(SpringJUnit4ClassRunner.class)
@SpringApplicationConfiguration(classes = SampleDataJpaApplication.class)
@WebIntegrationTest("server.port:0")
public class CityRepositoryIntegrationTests {

    @Autowired
    EmbeddedWebApplicationContext server;

    @Value("${local.server.port}")
    int port;

    // ...

}

68.6 Configure SSL

SSL can be configured declaratively by setting the various server.ssl.* properties, typically in application.properties or application.yml. For example:

server.port=8443
server.ssl.key-store=classpath:keystore.jks
server.ssl.key-store-password=secret
server.ssl.key-password=another-secret

See Ssl for details of all of the supported properties.

[Note]Note

Tomcat requires the key store (and trust store if you’re using one) to be directly accessible on the filesystem, i.e. it cannot be read from within a jar file. This limitation doesn’t apply to Jetty and Undertow.

Using configuration like the example above means the application will no longer support plain HTTP connector at port 8080. Spring Boot doesn’t support the configuration of both an HTTP connector and an HTTPS connector via application.properties. If you want to have both then you’ll need to configure one of them programmatically. It’s recommended to use application.properties to configure HTTPS as the HTTP connector is the easier of the two to configure programmatically. See the spring-boot-sample-tomcat-multi-connectors sample project for an example.

68.7 Configure Tomcat

Generally you can follow the advice from Section 67.7, “Discover built-in options for external properties” about @ConfigurationProperties (ServerProperties is the main one here), but also look at EmbeddedServletContainerCustomizer and various Tomcat-specific *Customizers that you can add in one of those. The Tomcat APIs are quite rich so once you have access to the TomcatEmbeddedServletContainerFactory you can modify it in a number of ways. Or the nuclear option is to add your own TomcatEmbeddedServletContainerFactory.

68.8 Enable Multiple Connectors with Tomcat

Add a org.apache.catalina.connector.Connector to the TomcatEmbeddedServletContainerFactory which can allow multiple connectors, e.g. HTTP and HTTPS connector:

@Bean
public EmbeddedServletContainerFactory servletContainer() {
    TomcatEmbeddedServletContainerFactory tomcat = new TomcatEmbeddedServletContainerFactory();
    tomcat.addAdditionalTomcatConnectors(createSslConnector());
    return tomcat;
}

private Connector createSslConnector() {
    Connector connector = new Connector("org.apache.coyote.http11.Http11NioProtocol");
    Http11NioProtocol protocol = (Http11NioProtocol) connector.getProtocolHandler();
    try {
        File keystore = new ClassPathResource("keystore").getFile();
        File truststore = new ClassPathResource("keystore").getFile();
        connector.setScheme("https");
        connector.setSecure(true);
        connector.setPort(8443);
        protocol.setSSLEnabled(true);
        protocol.setKeystoreFile(keystore.getAbsolutePath());
        protocol.setKeystorePass("changeit");
        protocol.setTruststoreFile(truststore.getAbsolutePath());
        protocol.setTruststorePass("changeit");
        protocol.setKeyAlias("apitester");
        return connector;
    }
    catch (IOException ex) {
        throw new IllegalStateException("can't access keystore: [" + "keystore"
                + "] or truststore: [" + "keystore" + "]", ex);
    }
}

68.9 Use Tomcat behind a front-end proxy server

Spring Boot will automatically configure Tomcat’s RemoteIpValve if you enable it. This allows you to transparently use the standard x-forwarded-for and x-forwarded-proto headers that most front-end proxy servers add. The valve is switched on by setting one or both of these properties to something non-empty (these are the conventional values used by most proxies, and if you only set one the other will be set automatically):

server.tomcat.remote_ip_header=x-forwarded-for
server.tomcat.protocol_header=x-forwarded-proto

If your proxy uses different headers you can customize the valve’s configuration by adding some entries to application.properties, e.g.

server.tomcat.remote_ip_header=x-your-remote-ip-header
server.tomcat.protocol_header=x-your-protocol-header

The valve is also configured with a default regular expression that matches internal proxies that are to be trusted. By default, IP addresses in 10/8, 192.168/16, 169.254/16 and 127/8 are trusted. You can customize the valve’s configuration by adding an entry to application.properties, e.g.

server.tomcat.internal_proxies=192\\.168\\.\\d{1,3}\\.\\d{1,3}
[Note]Note

The double backslashes are only required when you’re using a properties file for configuration. If you are using YAML, single backslashes are sufficient and a value that’s equivalent to the one shown above would be 192\.168\.\d{1,3}\.\d{1,3}.

Alternatively, you can take complete control of the configuration of the RemoteIpValve by configuring and adding it in a TomcatEmbeddedServletContainerFactory bean.

68.10 Use Jetty instead of Tomcat

The Spring Boot starters (spring-boot-starter-web in particular) use Tomcat as an embedded container by default. You need to exclude those dependencies and include the Jetty one instead. Spring Boot provides Tomcat and Jetty dependencies bundled together as separate starters to help make this process as easy as possible.

Example in Maven:

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-web</artifactId>
    <exclusions>
        <exclusion>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-tomcat</artifactId>
        </exclusion>
    </exclusions>
</dependency>
<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-jetty</artifactId>
</dependency>

Example in Gradle:

configurations {
    compile.exclude module: "spring-boot-starter-tomcat"
}

dependencies {
    compile("org.springframework.boot:spring-boot-starter-web:1.3.0.BUILD-SNAPSHOT")
    compile("org.springframework.boot:spring-boot-starter-jetty:1.3.0.BUILD-SNAPSHOT")
    // ...
}

68.11 Configure Jetty

Generally you can follow the advice from Section 67.7, “Discover built-in options for external properties” about @ConfigurationProperties (ServerProperties is the main one here), but also look at EmbeddedServletContainerCustomizer. The Jetty APIs are quite rich so once you have access to the JettyEmbeddedServletContainerFactory you can modify it in a number of ways. Or the nuclear option is to add your own JettyEmbeddedServletContainerFactory.

68.12 Use Undertow instead of Tomcat

Using Undertow instead of Tomcat is very similar to using Jetty instead of Tomcat. You need to exclude the Tomcat dependencies and include the Undertow starter instead.

Example in Maven:

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-web</artifactId>
    <exclusions>
        <exclusion>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-tomcat</artifactId>
        </exclusion>
    </exclusions>
</dependency>
<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-undertow</artifactId>
</dependency>

Example in Gradle:

configurations {
    compile.exclude module: "spring-boot-starter-tomcat"
}

dependencies {
    compile("org.springframework.boot:spring-boot-starter-web:1.3.0.BUILD-SNAPSHOT")
    compile("org.springframework.boot:spring-boot-starter-undertow:1.3.0.BUILD-SNAPSHOT")
    // ...
}

68.13 Configure Undertow

Generally you can follow the advice from Section 67.7, “Discover built-in options for external properties” about @ConfigurationProperties (ServerProperties and ServerProperties.Undertow are the main ones here), but also look at EmbeddedServletContainerCustomizer. Once you have access to the UndertowEmbeddedServletContainerFactory you can use an UndertowBuilderCustomizer to modify Undertow’s configuration to meet your needs. Or the nuclear option is to add your own UndertowEmbeddedServletContainerFactory.

68.14 Enable Multiple Listeners with Undertow

Add an UndertowBuilderCustomizer to the UndertowEmbeddedServletContainerFactory and add a listener to the Builder:

@Bean
public UndertowEmbeddedServletContainerFactory embeddedServletContainerFactory() {
    UndertowEmbeddedServletContainerFactory factory = new UndertowEmbeddedServletContainerFactory();
    factory.addBuilderCustomizers(new UndertowBuilderCustomizer() {

        @Override
        public void customize(Builder builder) {
            builder.addHttpListener(8080, "0.0.0.0");
        }

    });
    return factory;
}

68.15 Use Tomcat 7

Tomcat 7 works with Spring Boot, but the default is to use Tomcat 8. If you cannot use Tomcat 8 (for example, because you are using Java 1.6) you will need to change your classpath to reference Tomcat 7 .

68.15.1 Use Tomcat 7 with Maven

If you are using the starter poms and parent you can just change the Tomcat version property, e.g. for a simple webapp or service:

<properties>
    <tomcat.version>7.0.59</tomcat.version>
</properties>
<dependencies>
    ...
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-web</artifactId>
    </dependency>
    ...
</dependencies>

68.15.2 Use Tomcat 7 with Gradle

You can change the Tomcat version by setting the tomcat.version property:

ext['tomcat.version'] = '7.0.59'
dependencies {
    compile 'org.springframework.boot:spring-boot-starter-web'
}

68.16 Use Jetty 8

Jetty 8 works with Spring Boot, but the default is to use Jetty 9. If you cannot use Jetty 9 (for example, because you are using Java 1.6) you will need to change your classpath to reference Jetty 8. You will also need to exclude Jetty’s WebSocket-related dependencies.

68.16.1 Use Jetty 8 with Maven

If you are using the starter poms and parent you can just add the Jetty starter with the required WebSocket exclusion and change the version properties, e.g. for a simple webapp or service:

<properties>
    <jetty.version>8.1.15.v20140411</jetty.version>
    <jetty-jsp.version>2.2.0.v201112011158</jetty-jsp.version>
</properties>
<dependencies>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-web</artifactId>
        <exclusions>
            <exclusion>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-starter-tomcat</artifactId>
            </exclusion>
        </exclusions>
    </dependency>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-jetty</artifactId>
        <exclusions>
            <exclusion>
                <groupId>org.eclipse.jetty.websocket</groupId>
                <artifactId>*</artifactId>
            </exclusion>
        </exclusions>
    </dependency>
</dependencies>

68.16.2 Use Jetty 8 with Gradle

You can set the jetty.version property and exclude the WebSocket dependency, e.g. for a simple webapp or service:

ext['jetty.version'] = '8.1.15.v20140411'
dependencies {
    compile ('org.springframework.boot:spring-boot-starter-web') {
        exclude group: 'org.springframework.boot', module: 'spring-boot-starter-tomcat'
    }
    compile ('org.springframework.boot:spring-boot-starter-jetty') {
        exclude group: 'org.eclipse.jetty.websocket'
    }
}

68.17 Create WebSocket endpoints using @ServerEndpoint

If you want to use @ServerEndpoint in a Spring Boot application that used an embedded container, you must declare a single ServerEndpointExporter @Bean:

@Bean
public ServerEndpointExporter serverEndpointExporter() {
    return new ServerEndpointExporter();
}

This bean will register any @ServerEndpoint annotated beans with the underlying WebSocket container. When deployed to a standalone servlet container this role is performed by a servlet container initializer and the ServerEndpointExporter bean is not required.

68.18 Enable HTTP response compression

HTTP response compression is supported by Jetty, Tomcat, and Undertow. It can be enabled via application.properties:

server.compression.enabled=true

By default, responses must be at least 2048 bytes in length for compression to be performed. This can be configured using the server.compression.min-response-size property.

By default, responses will only be compressed if their content type is one of the following:

  • text/html
  • text/xml
  • text/plain
  • text/css

This can be configured using the server.compression.mime-types property.

69. Spring MVC

69.1 Write a JSON REST service

Any Spring @RestController in a Spring Boot application should render JSON response by default as long as Jackson2 is on the classpath. For example:

@RestController
public class MyController {

    @RequestMapping("/thing")
    public MyThing thing() {
            return new MyThing();
    }

}

As long as MyThing can be serialized by Jackson2 (e.g. a normal POJO or Groovy object) then localhost:8080/thing will serve a JSON representation of it by default. Sometimes in a browser you might see XML responses because browsers tend to send accept headers that prefer XML.

69.2 Write an XML REST service

If you have the Jackson XML extension (jackson-dataformat-xml) on the classpath, it will be used to render XML responses and the very same example as we used for JSON would work. To use it, add the following dependency to your project:

<dependency>
    <groupId>com.fasterxml.jackson.dataformat</groupId>
    <artifactId>jackson-dataformat-xml</artifactId>
</dependency>

You may also want to add a dependency on Woodstox. It’s faster than the default Stax implementation provided by the JDK and also adds pretty print support and improved namespace handling:

<dependency>
    <groupId>org.codehaus.woodstox</groupId>
    <artifactId>woodstox-core-asl</artifactId>
</dependency>

If Jackson’s XML extension is not available, JAXB (provided by default in the JDK) will be used, with the additional requirement to have MyThing annotated as @XmlRootElement:

@XmlRootElement
public class MyThing {
    private String name;
    // .. getters and setters
}

To get the server to render XML instead of JSON you might have to send an Accept: text/xml header (or use a browser).

69.3 Customize the Jackson ObjectMapper

Spring MVC (client and server side) uses HttpMessageConverters to negotiate content conversion in an HTTP exchange. If Jackson is on the classpath you already get the default converter(s) provided by Jackson2ObjectMapperBuilder.

The ObjectMapper (or XmlMapper for Jackson XML converter) instance created by default have the following customized properties:

  • MapperFeature.DEFAULT_VIEW_INCLUSION is disabled
  • DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES is disabled

Spring Boot has also some features to make it easier to customize this behavior.

You can configure the ObjectMapper and XmlMapper instances using the environment. Jackson provides an extensive suite of simple on/off features that can be used to configure various aspects of its processing. These features are described in six enums in Jackson which map onto properties in the environment:

Jackson enumEnvironment property

com.fasterxml.jackson.databind.DeserializationFeature

spring.jackson.deserialization.<feature_name>=true|false

com.fasterxml.jackson.core.JsonGenerator.Feature

spring.jackson.generator.<feature_name>=true|false

com.fasterxml.jackson.databind.MapperFeature

spring.jackson.mapper.<feature_name>=true|false

com.fasterxml.jackson.core.JsonParser.Feature

spring.jackson.parser.<feature_name>=true|false

com.fasterxml.jackson.databind.SerializationFeature

spring.jackson.serialization.<feature_name>=true|false

com.fasterxml.jackson.annotation.JsonInclude.Include

spring.jackson.serialization-inclusion=always|non_null|non_default|non_empty

For example, to enable pretty print, set spring.jackson.serialization.indent_output=true. Note that, thanks to the use of relaxed binding, the case of indent_output doesn’t have to match the case of the corresponding enum constant which is INDENT_OUTPUT.

If you want to replace the default ObjectMapper completely, define a @Bean of that type and mark it as @Primary.

Defining a @Bean of type Jackson2ObjectMapperBuilder will allow you to customize both default ObjectMapper and XmlMapper (used in MappingJackson2HttpMessageConverter and MappingJackson2XmlHttpMessageConverter respectively).

Another way to customize Jackson is to add beans of type com.fasterxml.jackson.databind.Module to your context. They will be registered with every bean of type ObjectMapper, providing a global mechanism for contributing custom modules when you add new features to your application.

Finally, if you provide any @Beans of type MappingJackson2HttpMessageConverter then they will replace the default value in the MVC configuration. Also, a convenience bean is provided of type HttpMessageConverters (always available if you use the default MVC configuration) which has some useful methods to access the default and user-enhanced message converters.

See also the Section 69.4, “Customize the @ResponseBody rendering” section and the WebMvcAutoConfiguration source code for more details.

69.4 Customize the @ResponseBody rendering

Spring uses HttpMessageConverters to render @ResponseBody (or responses from @RestController). You can contribute additional converters by simply adding beans of that type in a Spring Boot context. If a bean you add is of a type that would have been included by default anyway (like MappingJackson2HttpMessageConverter for JSON conversions) then it will replace the default value. A convenience bean is provided of type HttpMessageConverters (always available if you use the default MVC configuration) which has some useful methods to access the default and user-enhanced message converters (useful, for example if you want to manually inject them into a custom RestTemplate).

As in normal MVC usage, any WebMvcConfigurerAdapter beans that you provide can also contribute converters by overriding the configureMessageConverters method, but unlike with normal MVC, you can supply only additional converters that you need (because Spring Boot uses the same mechanism to contribute its defaults). Finally, if you opt-out of the Spring Boot default MVC configuration by providing your own @EnableWebMvc configuration, then you can take control completely and do everything manually using getMessageConverters from WebMvcConfigurationSupport.

See the WebMvcAutoConfiguration source code for more details.

69.5 Handling Multipart File Uploads

Spring Boot embraces the Servlet 3 javax.servlet.http.Part API to support uploading files. By default Spring Boot configures Spring MVC with a maximum file of 1Mb per file and a maximum of 10Mb of file data in a single request. You may override these values, as well as the location to which intermediate data is stored (e.g., to the /tmp directory) and the threshold past which data is flushed to disk by using the properties exposed in the MultipartProperties class. If you want to specify that files be unlimited, for example, set the multipart.maxFileSize property to -1.

The multipart support is helpful when you want to receive multipart encoded file data as a @RequestParam-annotated parameter of type MultipartFile in a Spring MVC controller handler method.

See the MultipartAutoConfiguration source for more details.

69.6 Switch off the Spring MVC DispatcherServlet

Spring Boot wants to serve all content from the root of your application / down. If you would rather map your own servlet to that URL you can do it, but of course you may lose some of the other Boot MVC features. To add your own servlet and map it to the root resource just declare a @Bean of type Servlet and give it the special bean name dispatcherServlet (You can also create a bean of a different type with that name if you want to switch it off and not replace it).

69.7 Switch off the Default MVC configuration

The easiest way to take complete control over MVC configuration is to provide your own @Configuration with the @EnableWebMvc annotation. This will leave all MVC configuration in your hands.

69.8 Customize ViewResolvers

A ViewResolver is a core component of Spring MVC, translating view names in @Controller to actual View implementations. Note that ViewResolvers are mainly used in UI applications, rather than REST-style services (a View is not used to render a @ResponseBody). There are many implementations of ViewResolver to choose from, and Spring on its own is not opinionated about which ones you should use. Spring Boot, on the other hand, installs one or two for you depending on what it finds on the classpath and in the application context. The DispatcherServlet uses all the resolvers it finds in the application context, trying each one in turn until it gets a result, so if you are adding your own you have to be aware of the order and in which position your resolver is added.

WebMvcAutoConfiguration adds the following ViewResolvers to your context:

  • An InternalResourceViewResolver with bean id ‘defaultViewResolver’. This one locates physical resources that can be rendered using the DefaultServlet (e.g. static resources and JSP pages if you are using those). It applies a prefix and a suffix to the view name and then looks for a physical resource with that path in the servlet context (defaults are both empty, but accessible for external configuration via spring.mvc.view.prefix and spring.mvc.view.suffix). It can be overridden by providing a bean of the same type.
  • A BeanNameViewResolver with id ‘beanNameViewResolver’. This is a useful member of the view resolver chain and will pick up any beans with the same name as the View being resolved. It shouldn’t be necessary to override or replace it.
  • A ContentNegotiatingViewResolver with id ‘viewResolver’ is only added if there are actually beans of type View present. This is a ‘master’ resolver, delegating to all the others and attempting to find a match to the ‘Accept’ HTTP header sent by the client. There is a useful blog about ContentNegotiatingViewResolver that you might like to study to learn more, and also look at the source code for detail. You can switch off the auto-configured ContentNegotiatingViewResolver by defining a bean named ‘viewResolver’.
  • If you use Thymeleaf you will also have a ThymeleafViewResolver with id ‘thymeleafViewResolver’. It looks for resources by surrounding the view name with a prefix and suffix (externalized to spring.thymeleaf.prefix and spring.thymeleaf.suffix, defaults ‘classpath:/templates/’ and ‘.html’ respectively). It can be overridden by providing a bean of the same name.
  • If you use FreeMarker you will also have a FreeMarkerViewResolver with id ‘freeMarkerViewResolver’. It looks for resources in a loader path (externalized to spring.freemarker.templateLoaderPath, default ‘classpath:/templates/’) by surrounding the view name with a prefix and suffix (externalized to spring.freemarker.prefix and spring.freemarker.suffix, with empty and ‘.ftl’ defaults respectively). It can be overridden by providing a bean of the same name.
  • If you use Groovy templates (actually if groovy-templates is on your classpath) you will also have a GroovyMarkupViewResolver with id ‘groovyMarkupViewResolver’. It looks for resources in a loader path by surrounding the view name with a prefix and suffix (externalized to spring.groovy.template.prefix and spring.groovy.template.suffix, defaults ‘classpath:/templates/’ and ‘.tpl’ respectively). It can be overriden by providing a bean of the same name.
  • If you use Velocity you will also have a VelocityViewResolver with id ‘velocityViewResolver’. It looks for resources in a loader path (externalized to spring.velocity.resourceLoaderPath, default ‘classpath:/templates/’) by surrounding the view name with a prefix and suffix (externalized to spring.velocity.prefix and spring.velocity.suffix, with empty and ‘.vm’ defaults respectively). It can be overridden by providing a bean of the same name.

Check out WebMvcAutoConfiguration, ThymeleafAutoConfiguration, FreeMarkerAutoConfiguration, GroovyTemplateAutoConfiguration and VelocityAutoConfiguration

70. Logging

Spring Boot has no mandatory logging dependence, except for the commons-logging API, of which there are many implementations to choose from. To use Logback you need to include it, and some bindings for commons-logging on the classpath. The simplest way to do that is through the starter poms which all depend on spring-boot-starter-logging. For a web application you only need spring-boot-starter-web since it depends transitively on the logging starter. For example, using Maven:

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-web</artifactId>
</dependency>

Spring Boot has a LoggingSystem abstraction that attempts to configure logging based on the content of the classpath. If Logback is available it is the first choice.

If the only change you need to make to logging is to set the levels of various loggers then you can do that in application.properties using the "logging.level" prefix, e.g.

logging.level.org.springframework.web=DEBUG
logging.level.org.hibernate=ERROR

You can also set the location of a file to log to (in addition to the console) using "logging.file".

To configure the more fine-grained settings of a logging system you need to use the native configuration format supported by the LoggingSystem in question. By default Spring Boot picks up the native configuration from its default location for the system (e.g. classpath:logback.xml for Logback), but you can set the location of the config file using the "logging.config" property.

70.1 Configure Logback for logging

If you put a logback-spring.xml in the root of your classpath it will be picked up from there. Spring Boot provides a default base configuration that you can include if you just want to set levels, e.g.

<?xml version="1.0" encoding="UTF-8"?>
<configuration>
    <include resource="org/springframework/boot/logging/logback/base.xml"/>
    <logger name="org.springframework.web" level="DEBUG"/>
</configuration>

If you look at the default logback.xml in the spring-boot jar you will see that it uses some useful System properties which the LoggingSystem takes care of creating for you. These are:

  • ${PID} the current process ID.
  • ${LOG_FILE} if logging.file was set in Boot’s external configuration.
  • ${LOG_PATH} if logging.path was set (representing a directory for log files to live in).

Spring Boot also provides some nice ANSI colour terminal output on a console (but not in a log file) using a custom Logback converter. See the default base.xml configuration for details.

If Groovy is on the classpath you should be able to configure Logback with logback.groovy as well (it will be given preference if present).

70.2 Configure Log4j for logging

Spring Boot also supports either Log4j or Log4j 2 for logging configuration, but only if one of them is on the classpath. If you are using the starter poms for assembling dependencies that means you have to exclude Logback and then include your chosen version of Log4j instead. If you aren’t using the starter poms then you need to provide commons-logging (at least) in addition to your chosen version of Log4j.

The simplest path is probably through the starter poms, even though it requires some jiggling with excludes, .e.g. in Maven:

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-web</artifactId>
</dependency>
<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter</artifactId>
    <exclusions>
        <exclusion>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-logging</artifactId>
        </exclusion>
    </exclusions>
</dependency>
<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-log4j</artifactId>
</dependency>

To use Log4j 2, simply depend on spring-boot-starter-log4j2 rather than spring-boot-starter-log4j.

[Note]Note

The use of one of the Log4j starters gathers together the dependencies for common logging requirements (e.g. including having Tomcat use java.util.logging but configuring the output using Log4j or Log4j 2). See the Actuator Log4j or Log4j 2 samples for more detail and to see it in action.

70.2.1 Use YAML or JSON to configure Log4j 2

In addition to its default XML configuration format, Log4j 2 also supports YAML and JSON configuration files. To configure Log4j 2 to use an alternative configuration file format all you need to do is add an appropriate dependency to the classpath. To use YAML, add a dependency on com.fasterxml.jackson.dataformat:jackson-dataformat-yaml and Log4j 2 will look for configuration files names log4j2.yaml or log4j2.yml. To use JSON, add a dependency on com.fasterxml.jackson.core:jackson-databind and Log4j 2 will look for configuration files named log4j2.json or log4j2.jsn

71. Data Access

71.1 Configure a DataSource

To override the default settings just define a @Bean of your own of type DataSource. Spring Boot provides a utility builder class DataSourceBuilder that can be used to create one of the standard ones (if it is on the classpath), or you can just create your own, and bind it to a set of Environment properties as explained in Section 24.7.1, “Third-party configuration”, e.g.

@Bean
@ConfigurationProperties(prefix="datasource.mine")
public DataSource dataSource() {
    return new FancyDataSource();
}
datasource.mine.jdbcUrl=jdbc:h2:mem:mydb
datasource.mine.user=sa
datasource.mine.poolSize=30

See Section 29.1, “Configure a DataSource” in the ‘Spring Boot features’ section and the DataSourceAutoConfiguration class for more details.

71.2 Configure Two DataSources

Creating more than one data source works the same as creating the first one. You might want to mark one of them as @Primary if you are using the default auto-configuration for JDBC or JPA (then that one will be picked up by any @Autowired injections).

@Bean
@Primary
@ConfigurationProperties(prefix="datasource.primary")
public DataSource primaryDataSource() {
    return DataSourceBuilder.create().build();
}

@Bean
@ConfigurationProperties(prefix="datasource.secondary")
public DataSource secondaryDataSource() {
    return DataSourceBuilder.create().build();
}

71.3 Use Spring Data repositories

Spring Data can create implementations for you of @Repository interfaces of various flavors. Spring Boot will handle all of that for you as long as those @Repositories are included in the same package (or a sub-package) of your @EnableAutoConfiguration class.

For many applications all you will need is to put the right Spring Data dependencies on your classpath (there is a spring-boot-starter-data-jpa for JPA and a spring-boot-starter-data-mongodb for Mongodb), create some repository interfaces to handle your @Entity objects. Examples are in the JPA sample or the Mongodb sample.

Spring Boot tries to guess the location of your @Repository definitions, based on the @EnableAutoConfiguration it finds. To get more control, use the @EnableJpaRepositories annotation (from Spring Data JPA).

71.4 Separate @Entity definitions from Spring configuration

Spring Boot tries to guess the location of your @Entity definitions, based on the @EnableAutoConfiguration it finds. To get more control, you can use the @EntityScan annotation, e.g.

@Configuration
@EnableAutoConfiguration
@EntityScan(basePackageClasses=City.class)
public class Application {

    //...

}

71.5 Configure JPA properties

Spring Data JPA already provides some vendor-independent configuration options (e.g. for SQL logging) and Spring Boot exposes those, and a few more for hibernate as external configuration properties. The most common options to set are:

spring.jpa.hibernate.ddl-auto: create-drop
spring.jpa.hibernate.naming_strategy: org.hibernate.cfg.ImprovedNamingStrategy
spring.jpa.database: H2
spring.jpa.show-sql: true

(Because of relaxed data binding hyphens or underscores should work equally well as property keys.) The ddl-auto setting is a special case in that it has different defaults depending on whether you are using an embedded database (create-drop) or not (none). In addition all properties in spring.jpa.properties.* are passed through as normal JPA properties (with the prefix stripped) when the local EntityManagerFactory is created.

See HibernateJpaAutoConfiguration and JpaBaseConfiguration for more details.

71.6 Use a custom EntityManagerFactory

To take full control of the configuration of the EntityManagerFactory, you need to add a @Bean named ‘entityManagerFactory’. Spring Boot auto-configuration switches off its entity manager based on the presence of a bean of that type.

71.7 Use Two EntityManagers

Even if the default EntityManagerFactory works fine, you will need to define a new one because otherwise the presence of the second bean of that type will switch off the default. To make it easy to do that you can use the convenient EntityManagerBuilder provided by Spring Boot, or if you prefer you can just use the LocalContainerEntityManagerFactoryBean directly from Spring ORM.

Example:

// add two data sources configured as above

@Bean
public LocalContainerEntityManagerFactoryBean customerEntityManagerFactory(
        EntityManagerFactoryBuilder builder) {
    return builder
            .dataSource(customerDataSource())
            .packages(Customer.class)
            .persistenceUnit("customers")
            .build();
}

@Bean
public LocalContainerEntityManagerFactoryBean orderEntityManagerFactory(
        EntityManagerFactoryBuilder builder) {
    return builder
            .dataSource(orderDataSource())
            .packages(Order.class)
            .persistenceUnit("orders")
            .build();
}

The configuration above almost works on its own. To complete the picture you need to configure TransactionManagers for the two EntityManagers as well. One of them could be picked up by the default JpaTransactionManager in Spring Boot if you mark it as @Primary. The other would have to be explicitly injected into a new instance. Or you might be able to use a JTA transaction manager spanning both.

71.8 Use a traditional persistence.xml

Spring doesn’t require the use of XML to configure the JPA provider, and Spring Boot assumes you want to take advantage of that feature. If you prefer to use persistence.xml then you need to define your own @Bean of type LocalEntityManagerFactoryBean (with id ‘entityManagerFactory’, and set the persistence unit name there.

See JpaBaseConfiguration for the default settings.

71.9 Use Spring Data JPA and Mongo repositories

Spring Data JPA and Spring Data Mongo can both create Repository implementations for you automatically. If they are both present on the classpath, you might have to do some extra configuration to tell Spring Boot which one (or both) you want to create repositories for you. The most explicit way to do that is to use the standard Spring Data @Enable*Repositories and tell it the location of your Repository interfaces (where ‘*’ is ‘Jpa’ or ‘Mongo’ or both).

There are also flags spring.data.*.repositories.enabled that you can use to switch the auto-configured repositories on and off in external configuration. This is useful for instance in case you want to switch off the Mongo repositories and still use the auto-configured MongoTemplate.

The same obstacle and the same features exist for other auto-configured Spring Data repository types (Elasticsearch, Solr). Just change the names of the annotations and flags respectively.

71.10 Expose Spring Data repositories as REST endpoint

Spring Data REST can expose the Repository implementations as REST endpoints for you as long as Spring MVC has been enabled for the application.

Spring Boot exposes as set of useful properties from the spring.data.rest namespace that customize the RepositoryRestConfiguration. If you need to provide additional customization, you can create a @Configuration class that extends SpringBootRepositoryRestMvcConfiguration. This class supports the same functionality as RepositoryRestMvcConfiguration, but allows you to continue using spring.data.rest.* properties.

72. Database initialization

An SQL database can be initialized in different ways depending on what your stack is. Or of course you can do it manually as long as the database is a separate process.

72.1 Initialize a database using JPA

JPA has features for DDL generation, and these can be set up to run on startup against the database. This is controlled through two external properties:

  • spring.jpa.generate-ddl (boolean) switches the feature on and off and is vendor independent.
  • spring.jpa.hibernate.ddl-auto (enum) is a Hibernate feature that controls the behavior in a more fine-grained way. See below for more detail.

72.2 Initialize a database using Hibernate

You can set spring.jpa.hibernate.ddl-auto explicitly and the standard Hibernate property values are none, validate, update, create, create-drop. Spring Boot chooses a default value for you based on whether it thinks your database is embedded (default create-drop) or not (default none). An embedded database is detected by looking at the Connection type: hsqldb, h2 and derby are embedded, the rest are not. Be careful when switching from in-memory to a ‘real’ database that you don’t make assumptions about the existence of the tables and data in the new platform. You either have to set ddl-auto explicitly, or use one of the other mechanisms to initialize the database.

[Note]Note

You can output the schema creation by enabling the org.hibernate.SQL logger. This is done for you automatically if you enable the debug mode.

In addition, a file named import.sql in the root of the classpath will be executed on startup. This can be useful for demos and for testing if you are careful, but probably not something you want to be on the classpath in production. It is a Hibernate feature (nothing to do with Spring).

72.3 Initialize a database using Spring JDBC

Spring JDBC has a DataSource initializer feature. Spring Boot enables it by default and loads SQL from the standard locations schema.sql and data.sql (in the root of the classpath). In addition Spring Boot will load the schema-${platform}.sql and data-${platform}.sql files (if present), where platform is the value of spring.datasource.platform, e.g. you might choose to set it to the vendor name of the database (hsqldb, h2, oracle, mysql, postgresql etc.). Spring Boot enables the failfast feature of the Spring JDBC initializer by default, so if the scripts cause exceptions the application will fail to start. The script locations can be changed by setting spring.datasource.schema and spring.datasource.data, and neither location will be processed if spring.datasource.initialize=false.

To disable the failfast you can set spring.datasource.continueOnError=true. This can be useful once an application has matured and been deployed a few times, since the scripts can act as ‘poor man’s migrations’ — inserts that fail mean that the data is already there, so there would be no need to prevent the application from running, for instance.

If you want to use the schema.sql initialization in a JPA app (with Hibernate) then ddl-auto=create-drop will lead to errors if Hibernate tries to create the same tables. To avoid those errors set ddl-auto explicitly to "" (preferable) or "none". Whether or not you use ddl-auto=create-drop you can always use data.sql to initialize new data.

72.4 Initialize a Spring Batch database

If you are using Spring Batch then it comes pre-packaged with SQL initialization scripts for most popular database platforms. Spring Boot will detect your database type, and execute those scripts by default, and in this case will switch the fail fast setting to false (errors are logged but do not prevent the application from starting). This is because the scripts are known to be reliable and generally do not contain bugs, so errors are ignorable, and ignoring them makes the scripts idempotent. You can switch off the initialization explicitly using spring.batch.initializer.enabled=false.

72.5 Use a higher level database migration tool

Spring Boot works fine with higher level migration tools Flyway (SQL-based) and Liquibase (XML). In general we prefer Flyway because it is easier on the eyes, and it isn’t very common to need platform independence: usually only one or at most couple of platforms is needed.

72.5.1 Execute Flyway database migrations on startup

To automatically run Flyway database migrations on startup, add the org.flywaydb:flyway-core to your classpath.

The migrations are scripts in the form V<VERSION>__<NAME>.sql (with <VERSION> an underscore-separated version, e.g. ‘1’ or ‘2_1’). By default they live in a folder classpath:db/migration but you can modify that using flyway.locations (a list). See the Flyway class from flyway-core for details of available settings like schemas etc. In addition Spring Boot provides a small set of properties in FlywayProperties that can be used to disable the migrations, or switch off the location checking.

By default Flyway will autowire the (@Primary) DataSource in your context and use that for migrations. If you like to use a different DataSource you can create one and mark its @Bean as @FlywayDataSource - if you do that remember to create another one and mark it as @Primary if you want two data sources. Or you can use Flyway’s native DataSource by setting flyway.[url,user,password] in external properties.

There is a Flyway sample so you can see how to set things up.

72.5.2 Execute Liquibase database migrations on startup

To automatically run Liquibase database migrations on startup, add the org.liquibase:liquibase-core to your classpath.

The master change log is by default read from db/changelog/db.changelog-master.yaml but can be set using liquibase.change-log. See LiquibaseProperties for details of available settings like contexts, default schema etc.

There is a Liquibase sample so you can see how to set things up.

73. Batch applications

73.1 Execute Spring Batch jobs on startup

Spring Batch auto configuration is enabled by adding @EnableBatchProcessing (from Spring Batch) somewhere in your context.

By default it executes all Jobs in the application context on startup (see JobLauncherCommandLineRunner for details). You can narrow down to a specific job or jobs by specifying spring.batch.job.names (comma-separated job name patterns).

If the application context includes a JobRegistry then the jobs in spring.batch.job.names are looked up in the registry instead of being autowired from the context. This is a common pattern with more complex systems where multiple jobs are defined in child contexts and registered centrally.

See BatchAutoConfiguration and @EnableBatchProcessing for more details.

74. Actuator

74.1 Change the HTTP port or address of the actuator endpoints

In a standalone application the Actuator HTTP port defaults to the same as the main HTTP port. To make the application listen on a different port set the external property management.port. To listen on a completely different network address (e.g. if you have an internal network for management and an external one for user applications) you can also set management.address to a valid IP address that the server is able to bind to.

For more detail look at the ManagementServerProperties source code and Section 45.3, “Customizing the management server port” in the ‘Production-ready features’ section.

74.2 Customize the ‘whitelabel’ error page

Spring Boot installs a ‘whitelabel’ error page that you will see in browser client if you encounter a server error (machine clients consuming JSON and other media types should see a sensible response with the right error code). To switch it off you can set error.whitelabel.enabled=false, but normally in addition or alternatively to that you will want to add your own error page replacing the whitelabel one. Exactly how you do this depends on the templating technology that you are using. For example, if you are using Thymeleaf you would add an error.html template and if you are using FreeMarker you would add an error.ftl template. In general what you need is a View that resolves with a name of error, and/or a @Controller that handles the /error path. Unless you replaced some of the default configuration you should find a BeanNameViewResolver in your ApplicationContext so a @Bean with id error would be a simple way of doing that. Look at ErrorMvcAutoConfiguration for more options.

See also the section on Error Handling for details of how to register handlers in the servlet container.

75. Security

75.1 Switch off the Spring Boot security configuration

If you define a @Configuration with @EnableWebSecurity anywhere in your application it will switch off the default webapp security settings in Spring Boot. To tweak the defaults try setting properties in security.* (see SecurityProperties for details of available settings) and SECURITY section of Common application properties.

75.2 Change the AuthenticationManager and add user accounts

If you provide a @Bean of type AuthenticationManager the default one will not be created, so you have the full feature set of Spring Security available (e.g. various authentication options).

Spring Security also provides a convenient AuthenticationManagerBuilder which can be used to build an AuthenticationManager with common options. The recommended way to use this in a webapp is to inject it into a void method in a WebSecurityConfigurerAdapter, e.g.

@Configuration
public class SecurityConfiguration extends WebSecurityConfigurerAdapter {

    @Autowired
    public void configureGlobal(AuthenticationManagerBuilder auth) throws Exception {
            auth.inMemoryAuthentication()
                .withUser("barry").password("password").roles("USER"); // ... etc.
    }

    // ... other stuff for application security

}

You will get the best results if you put this in a nested class, or a standalone class (i.e. not mixed in with a lot of other @Beans that might be allowed to influence the order of instantiation). The secure web sample is a useful template to follow.

If you experience instantiation issues (e.g. using JDBC or JPA for the user detail store) it might be worth extracting the AuthenticationManagerBuilder callback into a GlobalAuthenticationConfigurerAdapter (in the init() method so it happens before the authentication manager is needed elsewhere), e.g.

@Configuration
public class AuthenticationManagerConfiguration extends

    GlobalAuthenticationConfigurerAdapter {
    @Override
    public void init(AuthenticationManagerBuilder auth) {
        auth.inMemoryAuthentication() // ... etc.
    }

}

75.3 Enable HTTPS when running behind a proxy server

Ensuring that all your main endpoints are only available over HTTPS is an important chore for any application. If you are using Tomcat as a servlet container, then Spring Boot will add Tomcat’s own RemoteIpValve automatically if it detects some environment settings, and you should be able to rely on the HttpServletRequest to report whether it is secure or not (even downstream of a proxy server that handles the real SSL termination). The standard behavior is determined by the presence or absence of certain request headers (x-forwarded-for and x-forwarded-proto), whose names are conventional, so it should work with most front end proxies. You can switch on the valve by adding some entries to application.properties, e.g.

server.tomcat.remote_ip_header=x-forwarded-for
server.tomcat.protocol_header=x-forwarded-proto

(The presence of either of those properties will switch on the valve. Or you can add the RemoteIpValve yourself by adding a TomcatEmbeddedServletContainerFactory bean.)

Spring Security can also be configured to require a secure channel for all (or some requests). To switch that on in a Spring Boot application you just need to set security.require_ssl to true in application.properties.

76. Hot swapping

76.1 Reload static content

There are several options for hot reloading. Running in an IDE (especially with debugging on) is a good way to do development (all modern IDEs allow reloading of static resources and usually also hot-swapping of Java class changes). The Maven and Gradle plugins also support running from the command line with reloading of static files. You can use that with an external css/js compiler process if you are writing that code with higher level tools.

The spring-boot-devtools module is also available with support for fast application restarts and LiveReload.

76.2 Reload templates without restarting the container

Most of the templating technologies supported by Spring Boot include a configuration option to disable caching (see below for details). If you’re using the spring-boot-devtools module these properties will be automatically configured for you at developement time.

76.2.1 Thymeleaf templates

If you are using Thymeleaf, then set spring.thymeleaf.cache to false. See ThymeleafAutoConfiguration for other Thymeleaf customization options.

76.2.2 FreeMarker templates

If you are using FreeMarker, then set spring.freemarker.cache to false. See FreeMarkerAutoConfiguration for other FreeMarker customization options.

76.2.3 Groovy templates

If you are using Groovy templates, then set spring.groovy.template.cache to false. See GroovyTemplateAutoConfiguration for other Groovy customization options.

76.2.4 Velocity templates

If you are using Velocity, then set spring.velocity.cache to false. See VelocityAutoConfiguration for other Velocity customization options.

76.3 Fast application restarts

The spring-boot-devtools module includes support for automatic application restarts. Whilst not as fast a technologies such as JRebel or Spring Loaded it’s usually significantly faster than a “cold start”. You should probably give it a try before investigating some of the more complex reload options discussed bellow.

For more details see the Chapter 20, Developer tools section.

76.4 Reload Java classes without restarting the container

Modern IDEs (Eclipse, IDEA, etc.) all support hot swapping of bytecode, so if you make a change that doesn’t affect class or method signatures it should reload cleanly with no side effects.

Spring Loaded goes a little further in that it can reload class definitions with changes in the method signatures. With some customization it can force an ApplicationContext to refresh itself (but there is no general mechanism to ensure that would be safe for a running application anyway, so it would only ever be a development time trick probably).

76.4.1 Configuring Spring Loaded for use with Maven

To use Spring Loaded with the Maven command line, just add it as a dependency in the Spring Boot plugin declaration, e.g.

<plugin>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-maven-plugin</artifactId>
    <dependencies>
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>springloaded</artifactId>
            <version>1.2.0.RELEASE</version>
        </dependency>
    </dependencies>
</plugin>

This normally works pretty well with Eclipse and IntelliJ IDEA as long as they have their build configuration aligned with the Maven defaults (Eclipse m2e does this out of the box).

76.4.2 Configuring Spring Loaded for use with Gradle and IntelliJ IDEA

You need to jump through a few hoops if you want to use Spring Loaded in combination with Gradle and IntelliJ IDEA. By default, IntelliJ IDEA will compile classes into a different location than Gradle, causing Spring Loaded monitoring to fail.

To configure IntelliJ IDEA correctly you can use the idea Gradle plugin:

buildscript {
    repositories { jcenter() }
    dependencies {
        classpath "org.springframework.boot:spring-boot-gradle-plugin:1.3.0.BUILD-SNAPSHOT"
        classpath 'org.springframework:springloaded:1.2.0.RELEASE'
    }
}

apply plugin: 'idea'

idea {
    module {
        inheritOutputDirs = false
        outputDir = file("$buildDir/classes/main/")
    }
}

// ...
[Note]Note

IntelliJ IDEA must be configured to use the same Java version as the command line Gradle task and springloaded must be included as a buildscript dependency.

You can also additionally enable ‘Make Project Automatically’ inside Intellij IDEA to automatically compile your code whenever a file is saved.

77. Build

77.1 Customize dependency versions with Maven

If you use a Maven build that inherits directly or indirectly from spring-boot-dependencies (for instance spring-boot-starter-parent) but you want to override a specific third-party dependency you can add appropriate <properties> elements. Browse the spring-boot-dependencies POM for a complete list of properties. For example, to pick a different slf4j version you would add the following:

<properties>
    <slf4j.version>1.7.5<slf4j.version>
</properties>
[Note]Note

This only works if your Maven project inherits (directly or indirectly) from spring-boot-dependencies. If you have added spring-boot-dependencies in your own dependencyManagement section with <scope>import</scope> you have to redefine the artifact yourself instead of overriding the property .

[Warning]Warning

Each Spring Boot release is designed and tested against a specific set of third-party dependencies. Overriding versions may cause compatibility issues.

77.2 Create an executable JAR with Maven

The spring-boot-maven-plugin can be used to create an executable ‘fat’ JAR. If you are using the spring-boot-starter-parent POM you can simply declare the plugin and your jars will be repackaged:

<build>
    <plugins>
        <plugin>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-maven-plugin</artifactId>
        </plugin>
    </plugins>
</build>

If you are not using the parent POM you can still use the plugin, however, you must additionally add an <executions> section:

<build>
    <plugins>
        <plugin>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-maven-plugin</artifactId>
            <version>1.3.0.BUILD-SNAPSHOT</version>
            <executions>
                <execution>
                    <goals>
                        <goal>repackage</goal>
                    </goals>
                </execution>
            </executions>
        </plugin>
    </plugins>
</build>

See the plugin documentation for full usage details.

77.3 Create an additional executable JAR

If you want to use your project as a library jar for other projects to depend on, and in addition have an executable (e.g. demo) version of it, you will want to configure the build in a slightly different way.

For Maven the normal JAR plugin and the Spring Boot plugin both have a ‘classifier’ configuration that you can add to create an additional JAR. Example (using the Spring Boot Starter Parent to manage the plugin versions and other configuration defaults):

<build>
    <plugins>
        <plugin>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-maven-plugin</artifactId>
            <configuration>
                <classifier>exec</classifier>
            </configuration>
        </plugin>
    </plugins>
</build>

Two jars are produced, the default one, and an executable one using the Boot plugin with classifier ‘exec’.

For Gradle users the steps are similar. Example:

bootRepackage  {
    classifier = 'exec'
}

77.4 Extract specific libraries when an executable jar runs

Most nested libraries in an executable jar do not need to be unpacked in order to run, however, certain libraries can have problems. For example, JRuby includes its own nested jar support which assumes that the jruby-complete.jar is always directly available as a file in its own right.

To deal with any problematic libraries, you can flag that specific nested jars should be automatically unpacked to the ‘temp folder’ when the executable jar first runs.

For example, to indicate that JRuby should be flagged for unpack using the Maven Plugin you would add the following configuration:

<build>
    <plugins>
        <plugin>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-maven-plugin</artifactId>
            <configuration>
                <requiresUnpack>
                    <dependency>
                        <groupId>org.jruby</groupId>
                        <artifactId>jruby-complete</artifactId>
                    </dependency>
                </requiresUnpack>
            </configuration>
        </plugin>
    </plugins>
</build>

And to do that same with Gradle:

springBoot  {
    requiresUnpack = ['org.jruby:jruby-complete']
}

77.5 Create a non-executable JAR with exclusions

Often if you have an executable and a non-executable jar as build products, the executable version will have additional configuration files that are not needed in a library jar. E.g. the application.yml configuration file might excluded from the non-executable JAR.

Here’s how to do that in Maven:

<build>
    <plugins>
        <plugin>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-maven-plugin</artifactId>
            <configuration>
                <classifier>exec</classifier>
            </configuration>
        </plugin>
        <plugin>
            <artifactId>maven-jar-plugin</artifactId>
            <executions>
                <execution>
                    <id>exec</id>
                    <phase>package</phase>
                    <goals>
                        <goal>jar</goal>
                    </goals>
                    <configuration>
                        <classifier>exec</classifier>
                    </configuration>
                </execution>
                <execution>
                    <phase>package</phase>
                    <goals>
                        <goal>jar</goal>
                    </goals>
                    <configuration>
                        <!-- Need this to ensure application.yml is excluded -->
                        <forceCreation>true</forceCreation>
                        <excludes>
                            <exclude>application.yml</exclude>
                        </excludes>
                    </configuration>
                </execution>
            </executions>
        </plugin>
    </plugins>
</build>

In Gradle you can create a new JAR archive with standard task DSL features, and then have the bootRepackage task depend on that one using its withJarTask property:

jar {
    baseName = 'spring-boot-sample-profile'
    version =  '0.0.0'
    excludes = ['**/application.yml']
}

task('execJar', type:Jar, dependsOn: 'jar') {
    baseName = 'spring-boot-sample-profile'
    version =  '0.0.0'
    classifier = 'exec'
    from sourceSets.main.output
}

bootRepackage  {
    withJarTask = tasks['execJar']
}

77.6 Remote debug a Spring Boot application started with Maven

To attach a remote debugger to a Spring Boot application started with Maven you can use the jvmArguments property of the maven plugin.

Check this example for more details.

77.7 Remote debug a Spring Boot application started with Gradle

To attach a remote debugger to a Spring Boot application started with Gradle you can use the applicationDefaultJvmArgs in build.gradle or --debug-jvm command line option.

build.gradle:

applicationDefaultJvmArgs = [
    "-agentlib:jdwp=transport=dt_socket,server=y,suspend=y,address=5005"
]

Command line:

$ gradle run --debug-jvm

Check Gradle Application Plugin for more details.

77.8 Build an executable archive from Ant without using spring-boot-antlib

To build with Ant you need to grab dependencies, compile and then create a jar or war archive as normal. To make it executable you can either use the spring-boot-antlib module, or you can follow these instructions:

  1. Use the appropriate launcher as a Main-Class, e.g. JarLauncher for a jar file, and specify the other properties it needs as manifest entries, principally a Start-Class.
  2. Add the runtime dependencies in a nested ‘lib’ directory (for a jar) and the provided (embedded container) dependencies in a nested lib-provided directory. Remember not to compress the entries in the archive.
  3. Add the spring-boot-loader classes at the root of the archive (so the Main-Class is available).

Example:

<target name="build" depends="compile">
    <copy todir="target/classes/lib">
        <fileset dir="lib/runtime" />
    </copy>
    <jar destfile="target/spring-boot-sample-actuator-${spring-boot.version}.jar" compress="false">
        <fileset dir="target/classes" />
        <fileset dir="src/main/resources" />
        <zipfileset src="lib/loader/spring-boot-loader-jar-${spring-boot.version}.jar" />
        <manifest>
            <attribute name="Main-Class" value="org.springframework.boot.loader.JarLauncher" />
            <attribute name="Start-Class" value="${start-class}" />
        </manifest>
    </jar>
</target>

The Actuator Sample has a build.xml that should work if you run it with

$ ant -lib <folder containing ivy-2.2.jar>

after which you can run the application with

$ java -jar target/*.jar

77.9 How to use Java 6

If you want to use Spring Boot with Java 6 there are a small number of configuration changes that you will have to make. The exact changes depend on your application’s functionality.

77.9.1 Embedded servlet container compatibility

If you are using one of Boot’s embedded Servlet containers you will have to use a Java 6-compatible container. Both Tomcat 7 and Jetty 8 are Java 6 compatible. See Section 68.15, “Use Tomcat 7” and Section 68.16, “Use Jetty 8” for details.

77.9.2 JTA API compatibility

While the Java Transaction API itself doesn’t require Java 7 the official API jar contains classes that have been built to require Java 7. If you are using JTA then you will need to replace the official JTA 1.2 API jar with one that has been built to work on Java 6. To do so, exclude any transitive dependencies on javax.transaction:javax.transaction-api and replace them with a dependency on org.jboss.spec.javax.transaction:jboss-transaction-api_1.2_spec:1.0.0.Final

78. Traditional deployment

78.1 Create a deployable war file

The first step in producing a deployable war file is to provide a SpringBootServletInitializer subclass and override its configure method. This makes use of Spring Framework’s Servlet 3.0 support and allows you to configure your application when it’s launched by the servlet container. Typically, you update your application’s main class to extend SpringBootServletInitializer:

@SpringBootApplication
public class Application extends SpringBootServletInitializer {

    @Override
    protected SpringApplicationBuilder configure(SpringApplicationBuilder application) {
        return application.sources(Application.class);
    }

    public static void main(String[] args) throws Exception {
        SpringApplication.run(Application.class, args);
    }

}

The next step is to update your build configuration so that your project produces a war file rather than a jar file. If you’re using Maven and using spring-boot-starter-parent (which configures Maven’s war plugin for you) all you need to do is modify pom.xml to change the packaging to war:

<packaging>war</packaging>

If you’re using Gradle, you need to modify build.gradle to apply the war plugin to the project:

apply plugin: 'war'

The final step in the process is to ensure that the embedded servlet container doesn’t interfere with the servlet container to which the war file will be deployed. To do so, you need to mark the embedded servlet container dependency as provided.

If you’re using Maven:

<dependencies>
    <!-- … -->
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-tomcat</artifactId>
        <scope>provided</scope>
    </dependency>
    <!-- … -->
</dependencies>

And if you’re using Gradle:

dependencies {
    // …
    providedRuntime 'org.springframework.boot:spring-boot-starter-tomcat'
    // …
}

If you’re using the Spring Boot build tools, marking the embedded servlet container dependency as provided will produce an executable war file with the provided dependencies packaged in a lib-provided directory. This means that, in addition to being deployable to a servlet container, you can also run your application using java -jar on the command line.

[Tip]Tip

Take a look at Spring Boot’s sample applications for a Maven-based example of the above-described configuration.

78.2 Create a deployable war file for older servlet containers

Older Servlet containers don’t have support for the ServletContextInitializer bootstrap process used in Servlet 3.0. You can still use Spring and Spring Boot in these containers but you are going to need to add a web.xml to your application and configure it to load an ApplicationContext via a DispatcherServlet.

78.3 Convert an existing application to Spring Boot

For a non-web application it should be easy (throw away the code that creates your ApplicationContext and replace it with calls to SpringApplication or SpringApplicationBuilder). Spring MVC web applications are generally amenable to first creating a deployable war application, and then migrating it later to an executable war and/or jar. Useful reading is in the Getting Started Guide on Converting a jar to a war.

Create a deployable war by extending SpringBootServletInitializer (e.g. in a class called Application), and add the Spring Boot @EnableAutoConfiguration annotation. Example:

@Configuration
@EnableAutoConfiguration
@ComponentScan
public class Application extends SpringBootServletInitializer {

    @Override
    protected SpringApplicationBuilder configure(SpringApplicationBuilder application) {
        // Customize the application or call application.sources(...) to add sources
        // Since our example is itself a @Configuration class we actually don't
        // need to override this method.
        return application;
    }

}

Remember that whatever you put in the sources is just a Spring ApplicationContext and normally anything that already works should work here. There might be some beans you can remove later and let Spring Boot provide its own defaults for them, but it should be possible to get something working first.

Static resources can be moved to /public (or /static or /resources or /META-INF/resources) in the classpath root. Same for messages.properties (Spring Boot detects this automatically in the root of the classpath).

Vanilla usage of Spring DispatcherServlet and Spring Security should require no further changes. If you have other features in your application, using other servlets or filters for instance, then you may need to add some configuration to your Application context, replacing those elements from the web.xml as follows:

  • A @Bean of type Servlet or ServletRegistrationBean installs that bean in the container as if it was a <servlet/> and <servlet-mapping/> in web.xml.
  • A @Bean of type Filter or FilterRegistrationBean behaves similarly (like a <filter/> and <filter-mapping/>.
  • An ApplicationContext in an XML file can be added to an @Import in your Application. Or simple cases where annotation configuration is heavily used already can be recreated in a few lines as @Bean definitions.

Once the war is working we make it executable by adding a main method to our Application, e.g.

public static void main(String[] args) {
    SpringApplication.run(Application.class, args);
}

Applications can fall into more than one category:

  • Servlet 3.0+ applications with no web.xml.
  • Applications with a web.xml.
  • Applications with a context hierarchy.
  • Applications without a context hierarchy.

All of these should be amenable to translation, but each might require slightly different tricks.

Servlet 3.0+ applications might translate pretty easily if they already use the Spring Servlet 3.0+ initializer support classes. Normally all the code from an existing WebApplicationInitializer can be moved into a SpringBootServletInitializer. If your existing application has more than one ApplicationContext (e.g. if it uses AbstractDispatcherServletInitializer) then you might be able to squash all your context sources into a single SpringApplication. The main complication you might encounter is if that doesn’t work and you need to maintain the context hierarchy. See the entry on building a hierarchy for examples. An existing parent context that contains web-specific features will usually need to be broken up so that all the ServletContextAware components are in the child context.

Applications that are not already Spring applications might be convertible to a Spring Boot application, and the guidance above might help, but your mileage may vary.

78.4 Deploying a WAR to Weblogic

To deploy a Spring Boot application to Weblogic you must ensure that your servlet initializer directly implements WebApplicationInitializer (even if you extend from a base class that already implements it).

A typical initializer for Weblogic would be something like this:

import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.boot.context.web.SpringBootServletInitializer;
import org.springframework.web.WebApplicationInitializer;

@SpringBootApplication
public class MyApplication extends SpringBootServletInitializer implements WebApplicationInitializer {

}

If you use logback, you will also need to tell Weblogic to prefer the packaged version rather than the version that pre-installed with the server. You can do this by adding a WEB-INF/weblogic.xml file with the following contents:

<?xml version="1.0" encoding="UTF-8"?>
<wls:weblogic-web-app
    xmlns:wls="http://xmlns.oracle.com/weblogic/weblogic-web-app"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://java.sun.com/xml/ns/javaee
        http://java.sun.com/xml/ns/javaee/ejb-jar_3_0.xsd
        http://xmlns.oracle.com/weblogic/weblogic-web-app
        http://xmlns.oracle.com/weblogic/weblogic-web-app/1.4/weblogic-web-app.xsd">
    <wls:container-descriptor>
        <wls:prefer-application-packages>
            <wls:package-name>org.slf4j</wls:package-name>
        </wls:prefer-application-packages>
    </wls:container-descriptor>
</wls:weblogic-web-app>

78.5 Deploying a WAR in an Old (Servlet 2.5) Container

Spring Boot uses Servlet 3.0 APIs to initialize the ServletContext (register Servlets etc.) so you can’t use the same application out of the box in a Servlet 2.5 container. It is however possible to run a Spring Boot application on an older container with some special tools. If you include org.springframework.boot:spring-boot-legacy as a dependency (maintained separately to the core of Spring Boot and currently available at 1.0.0.RELEASE), all you should need to do is create a web.xml and declare a context listener to create the application context and your filters and servlets. The context listener is a special purpose one for Spring Boot, but the rest of it is normal for a Spring application in Servlet 2.5. Example:

<?xml version="1.0" encoding="UTF-8"?>
<web-app version="2.5" xmlns="http://java.sun.com/xml/ns/javaee"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd">

    <context-param>
        <param-name>contextConfigLocation</param-name>
        <param-value>demo.Application</param-value>
    </context-param>

    <listener>
        <listener-class>org.springframework.boot.legacy.context.web.SpringBootContextLoaderListener</listener-class>
    </listener>

    <filter>
        <filter-name>metricFilter</filter-name>
        <filter-class>org.springframework.web.filter.DelegatingFilterProxy</filter-class>
    </filter>

    <filter-mapping>
        <filter-name>metricFilter</filter-name>
        <url-pattern>/*</url-pattern>
    </filter-mapping>

    <servlet>
        <servlet-name>appServlet</servlet-name>
        <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
        <init-param>
            <param-name>contextAttribute</param-name>
            <param-value>org.springframework.web.context.WebApplicationContext.ROOT</param-value>
        </init-param>
        <load-on-startup>1</load-on-startup>
    </servlet>

    <servlet-mapping>
        <servlet-name>appServlet</servlet-name>
        <url-pattern>/</url-pattern>
    </servlet-mapping>

</web-app>

In this example we are using a single application context (the one created by the context listener) and attaching it to the DispatcherServlet using an init parameter. This is normal in a Spring Boot application (you normally only have one application context).

Part IX. Appendices

Appendix A. Common application properties

Various properties can be specified inside your application.properties/application.yml file or as command line switches. This section provides a list common Spring Boot properties and references to the underlying classes that consume them.

[Note]Note

Property contributions can come from additional jar files on your classpath so you should not consider this an exhaustive list. It is also perfectly legit to define your own properties.

[Warning]Warning

This sample file is meant as a guide only. Do not copy/paste the entire content into your application; rather pick only the properties that you need.

# ===================================================================
# COMMON SPRING BOOT PROPERTIES
#
# This sample file is provided as a guideline. Do NOT copy it in its
# entirety to your own application.               ^^^
# ===================================================================

# ----------------------------------------
# CORE PROPERTIES
# ----------------------------------------

# BANNER
banner.charset=UTF-8 # banner file encoding
banner.location=classpath:banner.txt # banner file location

# SPRING CONFIG (ConfigFileApplicationListener)
spring.config.name= # config file name (default to 'application')
spring.config.location= # location of config file

# PROFILES
spring.profiles.active= # comma list of active profiles
spring.profiles.include= # unconditionally activate the specified comma separated profiles

# APPLICATION SETTINGS (SpringApplication)
spring.main.sources= # sources (class name, package name or XML resource location) to include
spring.main.web-environment= # detect by default
spring.main.show-banner=true
spring.main....= # see class for all properties

# ADMIN (SpringApplicationAdminJmxAutoConfiguration)
spring.application.admin.enabled=false # enable admin features for the application
spring.application.admin.jmx-name=org.springframework.boot:type=Admin,name=SpringApplication # JMX name of the application admin MBean

# OUTPUT
spring.output.ansi.enabled=detect # Configure the ANSI output ("detect", "always", "never")

# LOGGING
logging.path=/var/log
logging.file=myapp.log
logging.config= # location of config file (default classpath:logback.xml for logback)
logging.level.*= # levels for loggers, e.g. "logging.level.org.springframework=DEBUG" (TRACE, DEBUG, INFO, WARN, ERROR, FATAL, OFF)

# IDENTITY (ContextIdApplicationContextInitializer)
spring.application.name=
spring.application.index=

# EMBEDDED SERVER CONFIGURATION (ServerProperties)
server.port=8080
server.address= # bind to a specific NIC
server.session-timeout= # session timeout in seconds
server.compression.enabled=false # if response compression is enabled
server.compression.mime-types=text/html,text/xml,text/plain,text/css # comma-separated list of MIME types that should be compressed
server.compression.min-response-size=2048 # minimum response size that is required for compression to be performed
server.context-parameters.*= # Servlet context init parameters, e.g. server.context-parameters.a=alpha
server.context-path= # the context path, defaults to '/'
server.jsp-servlet.class-name=org.apache.jasper.servlet.JspServlet # The class name of the JSP servlet
server.jsp-servlet.init-parameters.*= # Init parameters used to configure the JSP servlet
server.jsp-servlet.registered=true # Whether or not the JSP servlet is registered
server.servlet-path= # the servlet path, defaults to '/'
server.display-name= # the display name of the application
server.ssl.enabled=true # if SSL support is enabled
server.ssl.client-auth= # want or need
server.ssl.key-alias=
server.ssl.ciphers= # supported SSL ciphers
server.ssl.key-password=
server.ssl.key-store=
server.ssl.key-store-password=
server.ssl.key-store-provider=
server.ssl.key-store-type=
server.ssl.protocol=TLS
server.ssl.trust-store=
server.ssl.trust-store-password=
server.ssl.trust-store-provider=
server.ssl.trust-store-type=
server.tomcat.access-log-pattern= # log pattern of the access log
server.tomcat.access-log-enabled=false # is access logging enabled
server.tomcat.internal-proxies=10\\.\\d{1,3}\\.\\d{1,3}\\.\\d{1,3}|\\
        192\\.168\\.\\d{1,3}\\.\\d{1,3}|\\
        169\\.254\\.\\d{1,3}\\.\\d{1,3}|\\
        127\\.\\d{1,3}\\.\\d{1,3}\\.\\d{1,3}|\\
        172\\.1[6-9]{1}\\.\\d{1,3}\\.\\d{1,3}|\\
        172\\.2[0-9]{1}\\.\\d{1,3}\\.\\d{1,3}|\\
        172\\.3[0-1]{1}\\.\\d{1,3}\\.\\d{1,3} # regular expression matching trusted IP addresses
server.tomcat.protocol-header=x-forwarded-proto # front end proxy forward header
server.tomcat.protocol-header-https-value=https # value of the protocol header that indicates that the incoming request uses SSL
server.tomcat.port-header= # front end proxy port header
server.tomcat.remote-ip-header=x-forwarded-for
server.tomcat.basedir=/tmp # base dir (usually not needed, defaults to tmp)
server.tomcat.background-processor-delay=30; # in seconds
server.tomcat.max-http-header-size= # maximum size in bytes of the HTTP message header
server.tomcat.max-threads = 0 # number of threads in protocol handler
server.tomcat.uri-encoding = UTF-8 # character encoding to use for URL decoding
server.undertow.access-log-enabled=false # if access logging is enabled
server.undertow.access-log-pattern=common # log pattern of the access log
server.undertow.access-log-dir=logs # access logs directory
server.undertow.buffer-size= # size of each buffer in bytes
server.undertow.buffers-per-region= # number of buffer per region
server.undertow.direct-buffers=false # allocate buffers outside the Java heap
server.undertow.io-threads= # number of I/O threads to create for the worker
server.undertow.worker-threads= # number of worker threads

# SPRING MVC (WebMvcProperties)
spring.mvc.locale= # set fixed locale, e.g. en_UK
spring.mvc.date-format= # set fixed date format, e.g. dd/MM/yyyy
spring.mvc.favicon.enabled=true
spring.mvc.message-codes-resolver-format= # PREFIX_ERROR_CODE / POSTFIX_ERROR_CODE
spring.mvc.ignore-default-model-on-redirect=true # if the the content of the "default" model should be ignored redirects
spring.mvc.async.request-timeout= # async request timeout in milliseconds
spring.mvc.view.prefix= # MVC view prefix
spring.mvc.view.suffix= # ... and suffix

# SPRING RESOURCES HANDLING (ResourceProperties)
spring.resources.cache-period= # cache timeouts in headers sent to browser
spring.resources.add-mappings=true # if default mappings should be added
spring.resources.chain.enabled=false # enable the Spring Resource Handling chain (enabled automatically if at least a strategy is enabled)
spring.resources.chain.cache=false # enable in-memory caching of resource resolution
spring.resources.chain.html-application-cache=false # enable HTML5 appcache manifest rewriting
spring.resources.chain.strategy.content.enabled=false # enable a content version strategy
spring.resources.chain.strategy.content.paths= # comma-separated list of regular expression patterns to apply the version strategy to
spring.resources.chain.strategy.fixed.enabled=false # enable a fixed version strategy
spring.resources.chain.strategy.fixed.paths= # comma-separated list of regular expression patterns to apply the version strategy to
spring.resources.chain.strategy.fixed.version= # version string to use for this version strategy

# MULTIPART (MultipartProperties)
multipart.enabled=true
multipart.file-size-threshold=0 # Threshold after which files will be written to disk.
multipart.location= # Intermediate location of uploaded files.
multipart.max-file-size=1Mb # Max file size.
multipart.max-request-size=10Mb # Max request size.

# SPRING HATEOAS (HateoasProperties)
spring.hateoas.apply-to-primary-object-mapper=true # if the primary mapper should also be configured

# HTTP encoding (HttpEncodingProperties)
spring.http.encoding.charset=UTF-8 # the encoding of HTTP requests/responses
spring.http.encoding.enabled=true # enable http encoding support
spring.http.encoding.force=true # force the configured encoding

# HTTP message conversion
spring.http.converters.preferred-json-mapper= # the preferred JSON mapper to use for HTTP message conversion. Set to "gson" to force the use of Gson when both it and Jackson are on the classpath.

# JACKSON (JacksonProperties)
spring.jackson.date-format= # Date format string (e.g. yyyy-MM-dd HH:mm:ss), or a fully-qualified date format class name (e.g. com.fasterxml.jackson.databind.util.ISO8601DateFormat)
spring.jackson.property-naming-strategy= # One of the constants on Jackson's PropertyNamingStrategy (e.g. CAMEL_CASE_TO_LOWER_CASE_WITH_UNDERSCORES) or the fully-qualified class name of a PropertyNamingStrategy subclass
spring.jackson.deserialization.*= # see Jackson's DeserializationFeature
spring.jackson.generator.*= # see Jackson's JsonGenerator.Feature
spring.jackson.joda-date-time-format= # Joda date time format string
spring.jackson.mapper.*= # see Jackson's MapperFeature
spring.jackson.parser.*= # see Jackson's JsonParser.Feature
spring.jackson.serialization.*= # see Jackson's SerializationFeature
spring.jackson.serialization-inclusion= # Controls the inclusion of properties during serialization (see Jackson's JsonInclude.Include)

# THYMELEAF (ThymeleafAutoConfiguration)
spring.thymeleaf.check-template-location=true
spring.thymeleaf.prefix=classpath:/templates/
spring.thymeleaf.excluded-view-names= # comma-separated list of view names that should be excluded from resolution
spring.thymeleaf.view-names= # comma-separated list of view names that can be resolved
spring.thymeleaf.suffix=.html
spring.thymeleaf.mode=HTML5
spring.thymeleaf.enabled=true # enable MVC view resolution
spring.thymeleaf.encoding=UTF-8
spring.thymeleaf.content-type=text/html # ;charset=<encoding> is added
spring.thymeleaf.cache=true # set to false for hot refresh

# FREEMARKER (FreeMarkerAutoConfiguration)
spring.freemarker.allow-request-override=false
spring.freemarker.cache=true
spring.freemarker.check-template-location=true
spring.freemarker.charset=UTF-8
spring.freemarker.content-type=text/html
spring.freemarker.enabled=true # enable MVC view resolution
spring.freemarker.expose-request-attributes=false
spring.freemarker.expose-session-attributes=false
spring.freemarker.expose-spring-macro-helpers=false
spring.freemarker.prefix=
spring.freemarker.prefer-file-system-access=true # prefer file system access for template loading
spring.freemarker.request-context-attribute=
spring.freemarker.settings.*=
spring.freemarker.suffix=.ftl
spring.freemarker.template-loader-path=classpath:/templates/ # comma-separated list
spring.freemarker.view-names= # whitelist of view names that can be resolved

# GROOVY TEMPLATES (GroovyTemplateAutoConfiguration)
spring.groovy.template.cache=true
spring.groovy.template.charset=UTF-8
spring.groovy.template.check-template-location=true # check that the templates location exists
spring.groovy.template.configuration.*= # See GroovyMarkupConfigurer
spring.groovy.template.content-type=text/html
spring.groovy.template.enabled=true # enable MVC view resolution
spring.groovy.template.prefix=classpath:/templates/
spring.groovy.template.suffix=.tpl
spring.groovy.template.view-names= # whitelist of view names that can be resolved

# VELOCITY TEMPLATES (VelocityAutoConfiguration)
spring.velocity.allow-request-override=false
spring.velocity.cache=true
spring.velocity.check-template-location=true
spring.velocity.charset=UTF-8
spring.velocity.content-type=text/html
spring.velocity.date-tool-attribute=
spring.velocity.enabled=true # enable MVC view resolution
spring.velocity.expose-request-attributes=false
spring.velocity.expose-session-attributes=false
spring.velocity.expose-spring-macro-helpers=false
spring.velocity.number-tool-attribute=
spring.velocity.prefer-file-system-access=true # prefer file system access for template loading
spring.velocity.prefix=
spring.velocity.properties.*=
spring.velocity.request-context-attribute=
spring.velocity.resource-loader-path=classpath:/templates/
spring.velocity.suffix=.vm
spring.velocity.toolbox-config-location= # velocity Toolbox config location, for example "/WEB-INF/toolbox.xml"
spring.velocity.view-names= # whitelist of view names that can be resolved

# MUSTACHE TEMPLATES (MustacheAutoConfiguration)
spring.mustache.cache=true
spring.mustache.charset=UTF-8
spring.mustache.check-template-location=true
spring.mustache.content-type=UTF-8
spring.mustache.enabled=true # enable MVC view resolution
spring.mustache.prefix=
spring.mustache.suffix=.html
spring.mustache.view-names= # whitelist of view names that can be resolved

# JERSEY (JerseyProperties)
spring.jersey.type=servlet # servlet or filter
spring.jersey.init= # init params
spring.jersey.filter.order=

# INTERNATIONALIZATION (MessageSourceAutoConfiguration)
spring.messages.basename=messages
spring.messages.cache-seconds=-1
spring.messages.encoding=UTF-8


# SECURITY (SecurityProperties)
security.user.name=user # login username
security.user.password= # login password
security.user.role=USER # role assigned to the user
security.require-ssl=false # advanced settings ...
security.enable-csrf=false
security.basic.enabled=true
security.basic.realm=Spring
security.basic.path= # /**
security.basic.authorize-mode= # ROLE, AUTHENTICATED, NONE
security.filter-order=0
security.headers.xss=false
security.headers.cache=false
security.headers.frame=false
security.headers.content-type=false
security.headers.hsts=all # none / domain / all
security.sessions=stateless # always / never / if_required / stateless
security.ignored= # Comma-separated list of paths to exclude from the default secured paths

# OAuth2 client (OAuth2ClientProperties
spring.oauth2.client.client-id= # OAuth2 client id
spring.oauth2.client.client-secret= # OAuth2 client secret. A random secret is generated by default

# OAuth2 SSO (OAuth2SsoProperties
spring.oauth2.sso.filter-order= # Filter order to apply if not providing an explicit WebSecurityConfigurerAdapter
spring.oauth2.sso.login-path= # Path to the login page, i.e. the one that triggers the redirect to the OAuth2 Authorization Server

# DATASOURCE (DataSourceAutoConfiguration & DataSourceProperties)
spring.datasource.name= # name of the data source
spring.datasource.initialize=true # populate using data.sql
spring.datasource.schema= # a schema (DDL) script resource reference
spring.datasource.data= # a data (DML) script resource reference
spring.datasource.sql-script-encoding= # a charset for reading SQL scripts
spring.datasource.platform= # the platform to use in the schema resource (schema-${platform}.sql)
spring.datasource.continue-on-error=false # continue even if can't be initialized
spring.datasource.separator=; # statement separator in SQL initialization scripts
spring.datasource.driver-class-name= # JDBC Settings...
spring.datasource.url=
spring.datasource.username=
spring.datasource.password=
spring.datasource.jndi-name= # For JNDI lookup (class, url, username & password are ignored when set)
spring.datasource.max-active=100 # Advanced configuration...
spring.datasource.max-idle=8
spring.datasource.min-idle=8
spring.datasource.initial-size=10
spring.datasource.validation-query=
spring.datasource.test-on-borrow=false
spring.datasource.test-on-return=false
spring.datasource.test-while-idle=
spring.datasource.time-between-eviction-runs-millis=
spring.datasource.min-evictable-idle-time-millis=
spring.datasource.max-wait=
spring.datasource.jmx-enabled=false # Export JMX MBeans (if supported)

# DAO (PersistenceExceptionTranslationAutoConfiguration)
spring.dao.exceptiontranslation.enabled=true

# MONGODB (MongoProperties)
spring.data.mongodb.host= # the db host
spring.data.mongodb.port=27017 # the connection port (defaults to 27107)
spring.data.mongodb.uri=mongodb://localhost/test # connection URL
spring.data.mongodb.database=
spring.data.mongodb.authentication-database=
spring.data.mongodb.grid-fs-database=
spring.data.mongodb.username=
spring.data.mongodb.password=
spring.data.mongodb.repositories.enabled=true # if spring data repository support is enabled
spring.data.mongodb.field-naming-strategy= # fully qualified name of the FieldNamingStrategy to use

# JPA (JpaBaseConfiguration, HibernateJpaAutoConfiguration)
spring.jpa.properties.*= # properties to set on the JPA connection
spring.jpa.open-in-view=true
spring.jpa.show-sql=true
spring.jpa.database-platform=
spring.jpa.database=
spring.jpa.generate-ddl=false # ignored by Hibernate, might be useful for other vendors
spring.jpa.hibernate.naming-strategy= # naming classname
spring.jpa.hibernate.ddl-auto= # defaults to create-drop for embedded dbs
spring.data.jpa.repositories.enabled=true # if spring data repository support is enabled

# JTA (JtaAutoConfiguration)
spring.jta.log-dir= # transaction log dir
spring.jta.*= # technology specific configuration

# JOOQ (JooqAutoConfiguration)
spring.jooq.sql-dialect=

# ATOMIKOS
spring.jta.atomikos.connectionfactory.borrow-connection-timeout=30 # Timeout, in seconds, for borrowing connections from the pool
spring.jta.atomikos.connectionfactory.ignore-session-transacted-flag=true # Whether or not to ignore the transacted flag when creating session
spring.jta.atomikos.connectionfactory.local-transaction-mode=false # Whether or not local transactions are desired
spring.jta.atomikos.connectionfactory.maintenance-interval=60 # The time, in seconds, between runs of the pool's maintenance thread
spring.jta.atomikos.connectionfactory.max-idle-time=60 # The time, in seconds, after which connections are cleaned up from the pool
spring.jta.atomikos.connectionfactory.max-lifetime=0 # The time, in seconds, that a connection can be pooled for before being destroyed. 0 denotes no limit.
spring.jta.atomikos.connectionfactory.max-pool-size=1 # The maximum size of the pool
spring.jta.atomikos.connectionfactory.min-pool-size=1 # The minimum size of the pool
spring.jta.atomikos.connectionfactory.reap-timeout=0 # The reap timeout, in seconds, for borrowed connections. 0 denotes no limit.
spring.jta.atomikos.connectionfactory.unique-resource-name=jmsConnectionFactory # The unique name used to identify the resource during recovery
spring.jta.atomikos.datasource.borrow-connection-timeout=30 # Timeout, in seconds, for borrowing connections from the pool
spring.jta.atomikos.datasource.default-isolation-level= # Default isolation level of connections provided by the pool
spring.jta.atomikos.datasource.login-timeout= # Timeout, in seconds, for establishing a database connection
spring.jta.atomikos.datasource.maintenance-interval=60 # The time, in seconds, between runs of the pool's maintenance thread
spring.jta.atomikos.datasource.max-idle-time=60 # The time, in seconds, after which connections are cleaned up from the pool
spring.jta.atomikos.datasource.max-lifetime=0 # The time, in seconds, that a connection can be pooled for before being destroyed. 0 denotes no limit.
spring.jta.atomikos.datasource.max-pool-size=1 # The maximum size of the pool
spring.jta.atomikos.datasource.min-pool-size=1 # The minimum size of the pool
spring.jta.atomikos.datasource.reap-timeout=0 # The reap timeout, in seconds, for borrowed connections. 0 denotes no limit.
spring.jta.atomikos.datasource.test-query= # SQL query or statement used to validate a connection before returning it
spring.jta.atomikos.datasource.unique-resource-name=dataSource # The unique name used to identify the resource during recovery

# BITRONIX
spring.jta.bitronix.connectionfactory.acquire-increment=1 # Number of connections to create when growing the pool
spring.jta.bitronix.connectionfactory.acquisition-interval=1 # Time, in seconds, to wait before trying to acquire a connection again after an invalid connection was acquired
spring.jta.bitronix.connectionfactory.acquisition-timeout=30 # Timeout, in seconds, for acquiring connections from the pool
spring.jta.bitronix.connectionfactory.allow-local-transactions=true # Whether or not the transaction manager should allow mixing XA and non-XA transactions
spring.jta.bitronix.connectionfactory.apply-transaction-timeout=false # Whether or not the transaction timeout should be set on the XAResource when it is enlisted
spring.jta.bitronix.connectionfactory.automatic-enlisting-enabled=true # Whether or not resources should be enlisted and delisted automatically
spring.jta.bitronix.connectionfactory.cache-producers-consumers=true # Whether or not produces and consumers should be cached
spring.jta.bitronix.connectionfactory.defer-connection-release=true # Whether or not the provider can run many transactions on the same connection and supports transaction interleaving
spring.jta.bitronix.connectionfactory.ignore-recovery-failures=false # Whether or not recovery failures should be ignored
spring.jta.bitronix.connectionfactory.max-idle-time=60 # The time, in seconds, after which connections are cleaned up from the pool
spring.jta.bitronix.connectionfactory.max-pool-size=10 # The maximum size of the pool. 0 denotes no limit
spring.jta.bitronix.connectionfactory.min-pool-size=0 # The minimum size of the pool
spring.jta.bitronix.connectionfactory.password= # The password to use to connect to the JMS provider
spring.jta.bitronix.connectionfactory.share-transaction-connections=false #  Whether or not connections in the ACCESSIBLE state can be shared within the context of a transaction
spring.jta.bitronix.connectionfactory.test-connections=true # Whether or not connections should be tested when acquired from the pool
spring.jta.bitronix.connectionfactory.two-pc-ordering-position=1 # The postion that this resource should take during two-phase commit (always first is Integer.MIN_VALUE, always last is Integer.MAX_VALUE)
spring.jta.bitronix.connectionfactory.unique-name=jmsConnectionFactory # The unique name used to identify the resource during recovery
spring.jta.bitronix.connectionfactory.use-tm-join=true Whether or not TMJOIN should be used when starting XAResources
spring.jta.bitronix.connectionfactory.user= # The user to use to connect to the JMS provider
spring.jta.bitronix.datasource.acquire-increment=1 # Number of connections to create when growing the pool
spring.jta.bitronix.datasource.acquisition-interval=1 # Time, in seconds, to wait before trying to acquire a connection again after an invalid connection was acquired
spring.jta.bitronix.datasource.acquisition-timeout=30 # Timeout, in seconds, for acquiring connections from the pool
spring.jta.bitronix.datasource.allow-local-transactions=true # Whether or not the transaction manager should allow mixing XA and non-XA transactions
spring.jta.bitronix.datasource.apply-transaction-timeout=false # Whether or not the transaction timeout should be set on the XAResource when it is enlisted
spring.jta.bitronix.datasource.automatic-enlisting-enabled=true # Whether or not resources should be enlisted and delisted automatically
spring.jta.bitronix.datasource.cursor-holdability= # The default cursor holdability for connections
spring.jta.bitronix.datasource.defer-connection-release=true # Whether or not the database can run many transactions on the same connection and supports transaction interleaving
spring.jta.bitronix.datasource.enable-jdbc4-connection-test= # Whether or not Connection.isValid() is called when acquiring a connection from the pool
spring.jta.bitronix.datasource.ignore-recovery-failures=false # Whether or not recovery failures should be ignored
spring.jta.bitronix.datasource.isolation-level= # The default isolation level for connections
spring.jta.bitronix.datasource.local-auto-commit= # The default auto-commit mode for local transactions
spring.jta.bitronix.datasource.login-timeout= # Timeout, in seconds, for establishing a database connection
spring.jta.bitronix.datasource.max-idle-time=60 # The time, in seconds, after which connections are cleaned up from the pool
spring.jta.bitronix.datasource.max-pool-size=10 # The maximum size of the pool. 0 denotes no limit
spring.jta.bitronix.datasource.min-pool-size=0 # The minimum size of the pool
spring.jta.bitronix.datasource.prepared-statement-cache-size=0 # The target size of the prepared statement cache. 0 disables the cache
spring.jta.bitronix.datasource.share-transaction-connections=false #  Whether or not connections in the ACCESSIBLE state can be shared within the context of a transaction
spring.jta.bitronix.datasource.test-query= # SQL query or statement used to validate a connection before returning it
spring.jta.bitronix.datasource.two-pc-ordering-position=1 # The position that this resource should take during two-phase commit (always first is Integer.MIN_VALUE, always last is Integer.MAX_VALUE)
spring.jta.bitronix.datasource.unique-name=dataSource # The unique name used to identify the resource during recovery
spring.jta.bitronix.datasource.use-tm-join=true Whether or not TMJOIN should be used when starting XAResources

# SOLR (SolrProperties)
spring.data.solr.host=http://127.0.0.1:8983/solr
spring.data.solr.zk-host=
spring.data.solr.repositories.enabled=true # if spring data repository support is enabled

# ELASTICSEARCH (ElasticsearchProperties)
spring.data.elasticsearch.cluster-name= # The cluster name (defaults to elasticsearch)
spring.data.elasticsearch.cluster-nodes= # The address(es) of the server node (comma-separated; if not specified starts a client node)
spring.data.elasticsearch.properties.*= # Additional properties used to configure the client
spring.data.elasticsearch.repositories.enabled=true # if spring data repository support is enabled

# DATA REST (RepositoryRestConfiguration)
spring.data.rest.base-path= # base path against which the exporter should calculate its links

# FLYWAY (FlywayProperties)
flyway.*= # Any public property available on the auto-configured `Flyway` object
flyway.check-location=false # check that migration scripts location exists
flyway.locations=classpath:db/migration # locations of migrations scripts
flyway.schemas= # schemas to update
flyway.init-version= 1 # version to start migration
flyway.init-sqls= # SQL statements to execute to initialize a connection immediately after obtaining it
flyway.sql-migration-prefix=V
flyway.sql-migration-suffix=.sql
flyway.enabled=true
flyway.url= # JDBC url if you want Flyway to create its own DataSource
flyway.user= # JDBC username if you want Flyway to create its own DataSource
flyway.password= # JDBC password if you want Flyway to create its own DataSource

# LIQUIBASE (LiquibaseProperties)
liquibase.change-log=classpath:/db/changelog/db.changelog-master.yaml
liquibase.check-change-log-location=true # check the change log location exists
liquibase.contexts= # runtime contexts to use
liquibase.default-schema= # default database schema to use
liquibase.drop-first=false
liquibase.enabled=true
liquibase.url= # specific JDBC url (if not set the default datasource is used)
liquibase.user= # user name for liquibase.url
liquibase.password= # password for liquibase.url

# JMX
spring.jmx.default-domain= # JMX domain name
spring.jmx.enabled=true # Expose MBeans from Spring
spring.jmx.server=mbeanServer # MBeanServer bean name

# RABBIT (RabbitProperties)
spring.rabbitmq.addresses= # connection addresses (e.g. myhost:9999,otherhost:1111)
spring.rabbitmq.dynamic=true # create an AmqpAdmin bean
spring.rabbitmq.host= # connection host
spring.rabbitmq.port= # connection port
spring.rabbitmq.password= # login password
spring.rabbitmq.requested-heartbeat= # requested heartbeat timeout, in seconds; zero for none
spring.rabbitmq.ssl.enabled=false # enable SSL support
spring.rabbitmq.ssl.key-store= # path to the key store that holds the SSL certificate
spring.rabbitmq.ssl.key-store-password= # password used to access the key store
spring.rabbitmq.ssl.trust-store= # trust store that holds SSL certificates
spring.rabbitmq.ssl.trust-store-password= # password used to access the trust store
spring.rabbitmq.username= # login user
spring.rabbitmq.virtual-host= # virtual host to use when connecting to the broker

# REDIS (RedisProperties)
spring.redis.database= # database name
spring.redis.host=localhost # server host
spring.redis.password= # server password
spring.redis.port=6379 # connection port
spring.redis.pool.max-idle=8 # pool settings ...
spring.redis.pool.min-idle=0
spring.redis.pool.max-active=8
spring.redis.pool.max-wait=-1
spring.redis.sentinel.master= # name of Redis server
spring.redis.sentinel.nodes= # comma-separated list of host:port pairs
spring.redis.timeout= # connection timeout in milliseconds

# ACTIVEMQ (ActiveMQProperties)
spring.activemq.broker-url=tcp://localhost:61616 # connection URL
spring.activemq.user=
spring.activemq.password=
spring.activemq.in-memory=true # broker kind to create if no broker-url is specified
spring.activemq.pooled=false

# ARTEMIS (ArtemisProperties)
spring.artemis.mode= # connection mode (native, embedded)
spring.artemis.host=localhost # hornetQ host (native mode)
spring.artemis.port=5445 # hornetQ port (native mode)
spring.artemis.embedded.enabled=true # if the embedded server is enabled (needs hornetq-jms-server.jar)
spring.artemis.embedded.server-id= # auto-generated id of the embedded server (integer)
spring.artemis.embedded.persistent=false # message persistence
spring.artemis.embedded.data-directory= # location of data content (when persistence is enabled)
spring.artemis.embedded.queues= # comma-separated queues to create on startup
spring.artemis.embedded.topics= # comma-separated topics to create on startup
spring.artemis.embedded.cluster-password= # customer password (randomly generated by default)

# HORNETQ (HornetQProperties)
spring.hornetq.mode= # connection mode (native, embedded)
spring.hornetq.host=localhost # hornetQ host (native mode)
spring.hornetq.port=5445 # hornetQ port (native mode)
spring.hornetq.embedded.enabled=true # if the embedded server is enabled (needs hornetq-jms-server.jar)
spring.hornetq.embedded.server-id= # auto-generated id of the embedded server (integer)
spring.hornetq.embedded.persistent=false # message persistence
spring.hornetq.embedded.data-directory= # location of data content (when persistence is enabled)
spring.hornetq.embedded.queues= # comma-separated queues to create on startup
spring.hornetq.embedded.topics= # comma-separated topics to create on startup
spring.hornetq.embedded.cluster-password= # customer password (randomly generated by default)

# JMS (JmsProperties)
spring.jms.jndi-name= # JNDI location of a JMS ConnectionFactory
spring.jms.pub-sub-domain= # false for queue (default), true for topic

# Email (MailProperties)
spring.mail.host=smtp.acme.org # mail server host
spring.mail.port= # mail server port
spring.mail.username=
spring.mail.password=
spring.mail.default-encoding=UTF-8 # encoding to use for MimeMessages
spring.mail.properties.*= # properties to set on the JavaMail session
spring.mail.jndi-name= # JNDI location of a Mail Session

# SPRING BATCH (BatchProperties)
spring.batch.job.names=job1,job2
spring.batch.job.enabled=true
spring.batch.initializer.enabled=true
spring.batch.schema= # batch schema to load
spring.batch.table-prefix= # table prefix for all the batch meta-data tables

# SPRING CACHE (CacheProperties)
spring.cache.type= # generic, ehcache, hazelcast, infinispan, jcache, redis, guava, simple, none
spring.cache.cache-names= # cache names to create on startup
spring.cache.ehcache.config= # location of the ehcache configuration
spring.cache.hazelcast.config= # location of the hazelcast configuration
spring.cache.infinispan.config= # location of the infinispan configuration
spring.cache.jcache.config= # location of jcache configuration
spring.cache.jcache.provider= # fully qualified name of the CachingProvider implementation to use
spring.cache.guava.spec= # guava specs

# AOP
spring.aop.auto=
spring.aop.proxy-target-class=

# FILE ENCODING (FileEncodingApplicationListener)
spring.mandatory-file-encoding= # Expected character encoding the application must use

# SPRING SOCIAL (SocialWebAutoConfiguration)
spring.social.auto-connection-views=true # Set to true for default connection views or false if you provide your own

# SPRING SOCIAL FACEBOOK (FacebookAutoConfiguration)
spring.social.facebook.app-id= # your application's Facebook App ID
spring.social.facebook.app-secret= # your application's Facebook App Secret

# SPRING SOCIAL LINKEDIN (LinkedInAutoConfiguration)
spring.social.linkedin.app-id= # your application's LinkedIn App ID
spring.social.linkedin.app-secret= # your application's LinkedIn App Secret

# SPRING SOCIAL TWITTER (TwitterAutoConfiguration)
spring.social.twitter.app-id= # your application's Twitter App ID
spring.social.twitter.app-secret= # your application's Twitter App Secret

# SPRING MOBILE SITE PREFERENCE (SitePreferenceAutoConfiguration)
spring.mobile.sitepreference.enabled=true # enabled by default

# SPRING MOBILE DEVICE VIEWS (DeviceDelegatingViewResolverAutoConfiguration)
spring.mobile.devicedelegatingviewresolver.enabled=true # disabled by default
spring.mobile.devicedelegatingviewresolver.enable-fallback= # enable support for fallback resolution, default to false.
spring.mobile.devicedelegatingviewresolver.normal-prefix=
spring.mobile.devicedelegatingviewresolver.normal-suffix=
spring.mobile.devicedelegatingviewresolver.mobile-prefix=mobile/
spring.mobile.devicedelegatingviewresolver.mobile-suffix=
spring.mobile.devicedelegatingviewresolver.tablet-prefix=tablet/
spring.mobile.devicedelegatingviewresolver.tablet-suffix=

# ----------------------------------------
# DEVTOOLS PROPERTIES
# ----------------------------------------

# DEVTOOLS (DevToolsProperties)
spring.devtools.restart.enabled=true # enable automatic restart
spring.devtools.restart.exclude= # patterns that should be excluding for triggering a full restart
spring.devtools.restart.poll-interval= # amount of time (in milliseconds) to wait between polling for classpath changes
spring.devtools.restart.quiet-period= # amount of quiet time (in milliseconds) required without any classpath changes before a restart is triggered
spring.devtools.restart.trigger-file= # name of a specific file that when changed will trigger the restart
spring.devtools.livereload.enabled=true # enable a livereload.com compatible server
spring.devtools.livereload.port=35729 # server port.

# REMOTE DEVTOOLS (RemoteDevToolsProperties)
spring.devtools.remote.context-path=/.~~spring-boot!~ # context path used to handle the remote connection
spring.devtools.remote.debug.enabled=true # enable remote debug support
spring.devtools.remote.debug.local-port=8000 # local remote debug server port
spring.devtools.remote.restart.enabled=true # enable remote restart
spring.devtools.remote.secret= # a shared secret required to establish a connection
spring.devtools.remote.secret-header-name=X-AUTH-TOKEN # HTTP header used to transfer the shared secret

# ----------------------------------------
# ACTUATOR PROPERTIES
# ----------------------------------------

# MANAGEMENT HTTP SERVER (ManagementServerProperties)
management.port= # defaults to 'server.port'
management.address= # bind to a specific NIC
management.context-path= # default to '/'
management.add-application-context-header= # default to true
management.security.enabled=true # enable security
management.security.role=ADMIN # role required to access the management endpoint
management.security.sessions=stateless # session creating policy to use (always, never, if_required, stateless)

# PID FILE (ApplicationPidFileWriter)
spring.pid.file= # Location of the PID file to write
spring.pid.fail-on-write-error= # Fail if the PID file cannot be written

# ENDPOINTS (AbstractEndpoint subclasses)
endpoints.autoconfig.id=autoconfig
endpoints.autoconfig.sensitive=true
endpoints.autoconfig.enabled=true
endpoints.beans.id=beans
endpoints.beans.sensitive=true
endpoints.beans.enabled=true
endpoints.configprops.id=configprops
endpoints.configprops.sensitive=true
endpoints.configprops.enabled=true
endpoints.configprops.keys-to-sanitize=password,secret,key,.*credentials.*,vcap_services # suffix or regex
endpoints.dump.id=dump
endpoints.dump.sensitive=true
endpoints.dump.enabled=true
endpoints.enabled=true # enable all endpoints
endpoints.env.id=env
endpoints.env.sensitive=true
endpoints.env.enabled=true
endpoints.env.keys-to-sanitize=password,secret,key,.*credentials.*,vcap_services # suffix or regex
endpoints.health.id=health
endpoints.health.sensitive=true
endpoints.health.enabled=true
endpoints.health.mapping.*= # mapping of health statuses to HttpStatus codes
endpoints.health.time-to-live=1000
endpoints.info.id=info
endpoints.info.sensitive=false
endpoints.info.enabled=true
endpoints.logfile.path=/logfile
endpoints.logfile.sensitive=true
endpoints.logfile.enabled=true
endpoints.mappings.enabled=true
endpoints.mappings.id=mappings
endpoints.mappings.sensitive=true
endpoints.metrics.id=metrics
endpoints.metrics.sensitive=true
endpoints.metrics.enabled=true
endpoints.shutdown.id=shutdown
endpoints.shutdown.sensitive=true
endpoints.shutdown.enabled=false
endpoints.trace.id=trace
endpoints.trace.sensitive=true
endpoints.trace.enabled=true

# ENDPOINTS CORS CONFIGURATION (MvcEndpointCorsProperties)
endpoints.cors.allow-credentials= # set whether user credentials are support. When not set, credentials are not supported.
endpoints.cors.allowed-origins= # comma-separated list of origins to allow. * allows all origins. When not set, CORS support is disabled.
endpoints.cors.allowed-methods= # comma-separated list of methods to allow. * allows all methods. When not set, defaults to GET.
endpoints.cors.allowed-headers= # comma-separated list of headers to allow in a request. * allows all headers.
endpoints.cors.exposed-headers= # comma-separated list of headers to include in a response.
endpoints.cors.max-age=1800 # how long, in seconds, the response from a pre-flight request can be cached by clients.

# HEALTH INDICATORS (previously health.*)
management.health.db.enabled=true
management.health.elasticsearch.enabled=true
management.health.elasticsearch.indices=  # comma-separated index names
management.health.elasticsearch.response-timeout=100 # the time, in milliseconds, to wait for a response from the cluster
management.health.diskspace.enabled=true
management.health.diskspace.path=.
management.health.diskspace.threshold=10485760
management.health.jms.enabled=true
management.health.mail.enabled=true
management.health.mongo.enabled=true
management.health.rabbit.enabled=true
management.health.redis.enabled=true
management.health.solr.enabled=true
management.health.status.order=DOWN, OUT_OF_SERVICE, UNKNOWN, UP

# MVC ONLY ENDPOINTS
endpoints.jolokia.path=/jolokia
endpoints.jolokia.sensitive=true
endpoints.jolokia.enabled=true # when using Jolokia

# JMX ENDPOINT (EndpointMBeanExportProperties)
endpoints.jmx.enabled=true # enable JMX export of all endpoints
endpoints.jmx.domain= # the JMX domain, defaults to 'org.springboot'
endpoints.jmx.unique-names=false
endpoints.jmx.static-names=

# JOLOKIA (JolokiaProperties)
jolokia.config.*= # See Jolokia manual

# REMOTE SHELL
shell.auth=simple # jaas, key, simple, spring
shell.command-refresh-interval=-1
shell.command-path-patterns= # classpath*:/commands/**, classpath*:/crash/commands/**
shell.config-path-patterns= # classpath*:/crash/*
shell.disabled-commands=jpa*,jdbc*,jndi* # comma-separated list of commands to disable
shell.disabled-plugins=false # don't expose plugins
shell.ssh.enabled= # ssh settings ...
shell.ssh.key-path=
shell.ssh.port=
shell.telnet.enabled= # telnet settings ...
shell.telnet.port=
shell.auth.jaas.domain= # authentication settings ...
shell.auth.key.path=
shell.auth.simple.user.name=
shell.auth.simple.user.password=
shell.auth.spring.roles=

# METRICS EXPORT (MetricExportProperties)
spring.metrics.export.enabled=true # flag to disable all metric exports (assuming any MetricWriters are available)
spring.metrics.export.delay-millis=5000 # delay in milliseconds between export ticks
spring.metrics.export.send-latest=true # flag to switch off any available optimizations based on not exporting unchanged metric values
spring.metrics.export.includes= # list of patterns for metric names to include
spring.metrics.export.excludes= # list of patterns for metric names to exclude. Applied after the includes
spring.metrics.export.redis.aggregate-key-pattern= # pattern that tells the aggregator what to do with the keys from the source repository
spring.metrics.export.redis.prefix=spring.metrics # prefix for redis repository if active
spring.metrics.export.redis.key=keys.spring.metrics # key for redis repository export (if active)
spring.metrics.export.triggers.*= # specific trigger properties per MetricWriter bean name

# SENDGRID (SendGridAutoConfiguration)
spring.sendgrid.username= # SendGrid account username
spring.sendgrid.password= # SendGrid account password
spring.sendgrid.proxy.host= # SendGrid proxy host
spring.sendgrid.proxy.port= # SendGrid proxy port

# GIT INFO
spring.git.properties= # resource ref to generated git info properties file

Appendix B. Configuration meta-data

Spring Boot jars are shipped with meta-data files that provide details of all supported configuration properties. The files are designed to allow IDE developers to offer contextual help and “code completion” as users are working with application.properties or application.yml files.

The majority of the meta-data file is generated automatically at compile time by processing all items annotated with @ConfigurationProperties. However, it is possible to write part of the meta-data manually for corner cases or more advanced use cases.

B.1 Meta-data format

Configuration meta-data files are located inside jars under META-INF/spring-configuration-metadata.json They use a simple JSON format with items categorized under either “groups” or “properties” and additional values hint categorized under "hints":

{"groups": [
    {
        "name": "server",
        "type": "org.springframework.boot.autoconfigure.web.ServerProperties",
        "sourceType": "org.springframework.boot.autoconfigure.web.ServerProperties"
    },
    {
        "name": "server.tomcat",
        "type": "org.springframework.boot.autoconfigure.web.ServerProperties$Tomcat",
        "sourceType": "org.springframework.boot.autoconfigure.web.ServerProperties",
        "sourceMethod": "getTomcat()"
    }
    ...
],"properties": [
    {
        "name": "server.port",
        "type": "java.lang.Integer",
        "sourceType": "org.springframework.boot.autoconfigure.web.ServerProperties"
    },
    {
        "name": "server.servlet-path",
        "type": "java.lang.String",
        "sourceType": "org.springframework.boot.autoconfigure.web.ServerProperties",