Build tool plugins

Spring Boot Maven plugin

The {spring-boot-maven-plugin-site}/[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	Refer to the {spring-boot-maven-plugin-site}/[Spring Boot Maven Plugin Site] for complete plugin documentation.

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>{spring-boot-version}</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>

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	See the “[howto-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 {spring-boot-maven-plugin-site}/[plugin info page].

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 omit version information from your build.gradle file for “blessed” dependencies.

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:{spring-boot-version}")
	}
}
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"
	}
	// ...
}

Declaring dependencies without versions

The spring-boot plugin will register a custom Gradle ResolutionStrategy with your build that allows you to omit version numbers when declaring dependencies to “blessed” artifacts. 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

The version of the spring-boot gradle plugin that you declare determines the actual versions of the “blessed” dependencies (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 spring-boot 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")
}

Custom version management

If is possible to customize the versions used by the ResolutionStrategy if you need to deviate from Spring Boot’s “blessed” dependencies. Alternative version metadata is consulted using the versionManagement configuration. For example:

dependencies {
	versionManagement("com.mycorp:mycorp-versions:1.0.0.RELEASE@properties")
	compile("org.springframework.data:spring-data-hadoop")
}

Version information needs to be published to a repository as a .properties file. For the above example mycorp-versions.properties file might contain the following:

org.springframework.data\:spring-data-hadoop=2.0.0.RELEASE

The properties file takes precedence over Spring Boot’s defaults, and can be used to override version numbers if necessary.

Default exclude rules

Gradle handles “exclude rules” in a slightly different way to Maven which can cause unexpected results when using the starter POMs. Specifically, exclusions declared on a dependency will not be applied when the dependency can be reached through a different path. For example, if a starter POM declares the following:

<dependencies>
	<dependency>
		<groupId>org.springframework</groupId>
		<artifactId>spring-core</artifactId>
		<version>4.0.5.RELEASE</version>
		<exclusions>
			<exclusion>
				<groupId>commons-logging</groupId>
				<artifactId>commons-logging</artifactId>
			</exclusion>
		</exclusions>
	</dependency>
	<dependency>
		<groupId>org.springframework</groupId>
		<artifactId>spring-context</artifactId>
		<version>4.0.5.RELEASE</version>
	</dependency>
</dependencies>

The commons-logging jar will not be excluded by Gradle because it is pulled in transitively via spring-context (spring-context → spring-core → commons-logging) which does not have an exclusion element.

To ensure that correct exclusions are actually applied, the Spring Boot Gradle plugin will automatically add exclusion rules. All exclusions defined in the spring-boot-dependencies POM and implicit rules for the “starter” POMs will be added.

If you don’t want exclusion rules automatically applied you can use the following configuration:

springBoot {
	applyExcludeRules=false
}

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	See the “[howto-create-a-deployable-war-file]” section for more details on how to create a deployable war file.

Running a project in-place

To run a project in place without building a jar first you can use the “bootRun” task:

$ gradle bootRun

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.

Note	Making static classpath resources reloadable means that `bootRun` does not use the output of the `processResources` task. When invoked using `bootRun` your application will use the resources in their unprocessed form.

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
}

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:

Name	Description
`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 whuch is used to populate the nested lib directory (without specifying this you get all compile and runtime dependencies).

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.

Configuration options

The following configuration options are available:

Name	Description
`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.

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.

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.

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 "{spring-boot-version}"
					}
				}
			}
		}
	}
}

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 "{spring-boot-version}"
								type "pom"
								scope "import"
							}
						}
					}
				}
			}
		}
	}
}

Supporting other build systems

If you want to use a build tool other than Maven or Gradle, 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.

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.

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.

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.

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));
			}
		});

What to read next

If you’re interested in how the build tool plugins work you can look at the {github-code}/spring-boot-tools[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.

Provide feedback

Saved searches

Use saved searches to filter your results more quickly

build-tool-plugins.adoc

build-tool-plugins.adoc

Build tool plugins

Spring Boot Maven plugin

Including the plugin

Packaging executable jar and war files

Spring Boot Gradle plugin

Including the plugin

Declaring dependencies without versions

Custom version management

Default exclude rules

Packaging executable jar and war files

Running a project in-place

Spring Boot plugin configuration

Repackage configuration

Repackage with custom Gradle configuration

Configuration options

Understanding how the Gradle plugin works

Publishing artifacts to a Maven repository using Gradle

Configuring Gradle to produce a pom that inherits dependency management

Configuring Gradle to produce a pom that imports dependency management

Supporting other build systems

Repackaging archives

Nested libraries

Finding a main class

Example repackage implementation

What to read next

Files

build-tool-plugins.adoc

Latest commit

History

build-tool-plugins.adoc

File metadata and controls

Build tool plugins

Spring Boot Maven plugin

Including the plugin

Packaging executable jar and war files

Spring Boot Gradle plugin

Including the plugin

Declaring dependencies without versions

Custom version management

Default exclude rules

Packaging executable jar and war files

Running a project in-place

Spring Boot plugin configuration

Repackage configuration

Repackage with custom Gradle configuration

Configuration options

Understanding how the Gradle plugin works

Publishing artifacts to a Maven repository using Gradle

Configuring Gradle to produce a pom that inherits dependency management

Configuring Gradle to produce a pom that imports dependency management

Supporting other build systems

Repackaging archives

Nested libraries

Finding a main class

Example repackage implementation

What to read next