23

The Java Plugin

The Java plugin adds Java compilation, testing and bundling capabilities to a project. It serves as the basis for many of the other Gradle plugins.

23.1. Usage

To use the Java plugin, include in your build script:

Example 23.1. Using the Java plugin

build.gradle

apply plugin: 'java'

23.2. Source sets

The Java plugin introduces the concept of a source set. A source set is simply a group of source files which are compiled and executed together. These source files may include Java source files and resource files. Other plugins add the ability to include Groovy and Scala source files in a source set. A source set has an associated compile classpath, and runtime classpath.

One use for source sets is to group source files into logical groups which describe their purpose. For example, you might use a source set to define an integration test suite, or you might use separate source sets to define the API and implementation classes of your project.

The Java plugin defines two standard source sets, called main and test. The main source set contains your production source code, which is compiled and assembled into a JAR file. The test source set contains your unit test source code, which is compiled and executed using JUnit or TestNG.

23.3. Tasks

The Java plugin adds a number of tasks to your project, as shown below.

Table 23.1. Java plugin - tasks

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Task name	Depends on	Type	Description
compileJava	All tasks which produce	Compile	Compiles production
	the compile classpath.		Java source files
	This includes the jar task		using javac.
	for project dependencies
	included in the compile
	configuration.
processResources	-	Copy	Copies production
			resources into the
			production classes
			directory.
classes	compileJava and processRTaskesources		Assembles the
	. Some plugins add		production classes
	additional compilation		directory.
	tasks.
compileTestJava	compile, plus all tasks	Compile	Compiles test Java
	which produce the test		source files using
	compile classpath.		javac.
processTestResources	-	Copy	Copies test
			resources into the
			test classes
			directory.
testClasses	compileTestJava and procesTaskTestResourcesAssembles the test
	. Some plugins add		classes directory.
	additional test compilation
	tasks.
jar	compile	Jar	Assembles the JAR
			file

javadoc

test

compile

compile, compileTest, plus all tasks which produce the test runtime classpath.

Javadoc Generates API documentation for the production Java source, using Javadoc

Test Runs the unit tests using JUnit or TestNG.

uploadArchives	The tasks which produce	Upload	Uploads the artifacts
	the artifacts in the archives		in the archives
	configuration, including jar		configuration,
	.		including the JAR
			file.
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clean	-	Delete	Deletes the project
			build directory.
cleanTaskName	-	Delete	Deletes the output
			files produced by
			the specified task.
			For example cleanJa
			will delete the JAR
			file created by the jar
			task, and cleanTest
			will delete the test
			results created by
			the test task.

For each source set you add to the project, the Java plugin adds the following compilation tasks:

Table 23.2. Java plugin - source set tasks

Task name	Depends on		Type	Description
compileSourceSetAll tasksJavawhich produce the source set's			Compile	Compiles the
	compile classpath.			given source
				set's Java
				source files
				using javac.
processSourceSet-		Resources	Copy	Copies the
				given source
				set's

resources into the classes directory.

sourceSetClassescompileSourceSetJava and processSourceSetTaskResourcesAssembles

. Some plugins add additional compilation tasks	the given
for the source set.	source set's
	classes
	directory.

The Java plugin also adds a number of tasks which form a lifecycle for the project:

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Table 23.3. Java plugin - lifecycle tasks
Task name	Depends on	Type
assemble	All archive tasks in the	Task
	project, including jar.
	Some plugins add
	additional archive tasks to
	the project.
check	All verification tasks in the	Task
	project, including test.
	Some plugins add
	additional verification
	tasks to the project.
build	check and assemble	Task
buildNeeded	build and build tasks in	Task
	all project lib
	dependencies of the testRuntime
	configuration.
buildDependents	build and build tasks in	Task
	all projects with a project
	lib dependency on this
	project in a testRuntime
	configuration.
buildConfigurationNameThe tasks which produce		Task
	the artifacts in
	configuration
	ConfigurationName.

uploadConfigurationNameThe tasks which uploads	Upload
the artifacts in
configuration
ConfigurationName.

Description

Assembles all the archives in the project.

Performs all verification tasks in the project.

Performs a full build of the project.

Performs a full build of the project and all projects it depends on.

Performs a full build of the project and all projects which depend on it.

Assembles the artifacts in the specified configuration. The task is added by the Base plugin which is implicitly applied by the Java plugin.

Assembles and uploads the artifacts in the specified configuration. The task is added by the Base plugin which is implicitly applied by the Java plugin.

The following diagram shows the relationships between these tasks.

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