翻译：Gradle之 Java插件

原文地址 http://www.gradle.org/docs/current/userguide/java_plugin.html

23.1. Usage用法

要使用Java插件，在脚本里加入:

Example 23.1. Using the Java plugin

build.gradle

apply plugin: 'java'

23.2. Source sets源集

Java插件引入了一个概念：源集（source set），一个源集就是一组被一起编译一起执行的源文件。这些文件可能包括Java源文件，也可以包括资源文件。有些插件增加了源集包含Groovy和Scala源文件的能力。一个源集具有一个相关的编译路径和运行时路径。

 源集的一个作用是将源文件进行逻辑分组来面熟共同的目的。比如可以使用源集定义一个集成测试套件，或用多个源集定义API和实现类。

java插件有两个标准源集：main 和test.。main 源集包含产品源代码，也就是要编译打包成jar的部分。test 源集包含单元测试源代码，编译后用JUnit 或TestNG执行。

23.3. Tasks任务

Java插件会给你的工程增加下面的任务：

Table 23.1. Java plugin - tasks

Task name	Depends on	Type	Description
compileJava	All tasks which produce the compile classpath. This includes the jar task for project dependencies included in thecompile configuration.	JavaCompile	Compiles production Java source files using javac.
processResources	-	Copy	Copies production resources into the production classes directory.
classes	compileJava and processResources. Some plugins add additional compilation tasks.	Task	Assembles the production classes directory.
compileTestJava	compile, plus all tasks which produce the test compile classpath.	JavaCompile	Compiles test Java source files using javac.
processTestResources	-	Copy	Copies test resources into the test classes directory.
testClasses	compileTestJava andprocessTestResources. Some plugins add additional test compilation tasks.	Task	Assembles the test classes directory.
jar	compile	Jar	Assembles the JAR file
javadoc	compile	Javadoc	Generates API documentation for the production Java source, using Javadoc
test	compile, compileTest, plus all tasks which produce the test runtime classpath.	Test	Runs the unit tests using JUnit or TestNG.
uploadArchives	The tasks which produce the artifacts in thearchives configuration, including jar.	Upload	Uploads the artifacts in the archives configuration, including the JAR file.
clean	-	Delete	Deletes the project build directory.
cleanTaskName	-	Delete	Deletes the output files produced by the specified task. For example cleanJar will delete the JAR file created by the jar task, and cleanTest will delete the test results created by the test task.

对于你加入工程的每一个源集，Java插件会增加如下编译任务：

Table 23.2. Java plugin - source set tasks

Task name	Depends on	Type	Description
compileSourceSetJava	All tasks which produce the source set's compile classpath.	JavaCompile	Compiles the given source set's Java source files using javac.
processSourceSetResources	-	Copy	Copies the given source set's resources into the classes directory.
sourceSetClasses	compileSourceSetJava and processSourceSetResources. Some plugins add additional compilation tasks for the source set.	Task	Assembles the given source set's classes directory.

Java插件也增加形成工程生命周期的任务：

Table 23.3. Java plugin - lifecycle tasks

Task name	Depends on	Type	Description
assemble	All archive tasks in the project, including jar. Some plugins add additional archive tasks to the project.	Task	Assembles all the archives in the project.
check	All verification tasks in the project, including test. Some plugins add additional verification tasks to the project.	Task	Performs all verification tasks in the project.
build	check and assemble	Task	Performs a full build of the project.
buildNeeded	build and build tasks in all project lib dependencies of thetestRuntime configuration.	Task	Performs a full build of the project and all projects it depends on.
buildDependents	build and build tasks in all projects with a project lib dependency on this project in a testRuntime configuration.	Task	Performs a full build of the project and all projects which depend on it.
buildConfigurationName	The tasks which produce the artifacts in configurationConfigurationName.	Task	Assembles the artifacts in the specified configuration. The task is added by the Base plugin which is implicitly applied by the Java plugin.
uploadConfigurationName	The tasks which uploads the artifacts in configurationConfigurationName.	Upload	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.

下图是任务间的关系：

Figure 23.1. Java plugin - tasks

23.4. Project layout工程布局

Java插件默认你的工程布局如下，任何目录都可以不存在，也可以不包含任何东西。java插件会编译它找到的任何东西，控制任何丢失的。

Table 23.4. Java plugin - default project layout

Directory	Meaning
src/main/java	Production Java source
src/main/resources	Production resources
src/test/java	Test Java source
src/test/resources	Test resources
src/sourceSet/java	Java source for the given source set
src/sourceSet/resources	Resources for the given source set

23.4.1. Changing the project layout改变工程布局

可以通过配置合适的源集来配置布局。后面还会详细讨论，下面是一个简单的例子修改了main中的 Java 和resource source 目录.

Example 23.2. Custom Java source layout

build.gradle

sourceSets {
    main {
        java {
            srcDir 'src/java'
        }
        resources {
            srcDir 'src/resources'
        }
    }
}

23.5. Dependency management依赖管理

Java插件有很多依赖配置，它把这些配置非给各个任务，如compileJava 和 test.

Table 23.5. Java plugin - dependency configurations

Name	Extends	Used by tasks	Meaning
compile	-	compileJava	Compile time dependencies
runtime	compile	-	Runtime dependencies
testCompile	compile	compileTestJava	Additional dependencies for compiling tests.
testRuntime	runtime, testCompile	test	Additional dependencies for running tests only.
archives	-	uploadArchives	Artifacts (e.g. jars) produced by this project.
default	runtime	-	The default configuration used by a project dependency on this project. Contains the artifacts and dependencies required by this project at runtime.

Figure 23.2. Java plugin - dependency configurations

对于加入工程的每个源集，Java插件增加如下依赖配置：

Table 23.6. Java plugin - source set dependency configurations

Name	Extends	Used by tasks	Meaning
sourceSetCompile	-	compileSourceSetJava	Compile time dependencies for the given source set
sourceSetRuntime	sourceSetCompile	-	Runtime time dependencies for the given source set

23.6. Convention properties传统属性

Java插件有一些传统属性，如下。你可以直接在脚本中使用这些属性，更多参考 Section 21.3, “Conventions”

Table 23.7. Java plugin - directory properties

Property name	Type	Default value	Description
reportsDirName	String	reports	The name of the directory to generate reports into, relative to the build directory.
reportsDir	File (read-only)	buildDir/reportsDirName	The directory to generate reports into.
testResultsDirName	String	test-results	The name of the directory to generate test result .xml files into, relative to the build directory.
testResultsDir	File (read-only)	buildDir/testResultsDirName	The directory to generate test result .xml files into.
testReportDirName	String	tests	The name of the directory to generate the test report into, relative to the reports directory.
testReportDir	File (read-only)	reportsDir/testReportDirName	The directory to generate the test report into.
libsDirName	String	libs	The name of the directory to generate libraries into, relative to the build directory.
libsDir	File (read-only)	buildDir/libsDirName	The directory to generate libraries into.
distsDirName	String	distributions	The name of the directory to generate distributions into, relative to the build directory.
distsDir	File (read-only)	buildDir/distsDirName	The directory to generate distributions into.
docsDirName	String	docs	The name of the directory to generate documentation into, relative to the build directory.
docsDir	File (read-only)	buildDir/docsDirName	The directory to generate documentation into.
dependencyCacheDirName	String	dependency-cache	The name of the directory to use to cache source dependency information, relative to the build directory.
dependencyCacheDir	File (read-only)	buildDir/dependencyCacheDirName	The directory to use to cache source dependency information.

Table 23.8. Java plugin - other properties

Property name	Type	Default value	Description
sourceSets	SourceSetContainer (read-only)	Not null	Contains the project's source sets.
sourceCompatibility	JavaVersion. Can also set using a String or a Number, e.g. '1.5' or1.5.	Value of the current used JVM	Java version compatibility to use when compiling Java source.
targetCompatibility	JavaVersion. Can also set using a String or Number, e.g. '1.5' or1.5.	sourceCompatibility	Java version to generate classes for.
archivesBaseName	String	projectName	The basename to use for archives, such as JAR or ZIP files.
manifest	Manifest	an empty manifest	The manifest to include in all JAR files.

这些属性来自传统对象：JavaPluginConvention, BasePluginConvention 和 ReportingBasePluginConvention.

23.7. Working with source sets使用源集

通过 sourceSets 属性访问源集，它是工程盛放源集的容器， SourceSetContainer类型的。 还有一个基本块 sourceSets { } ，可以使用闭包来配置源集容器。源集容器工作方式和其他容器完全一样，比如任务tasks.

Example 23.3. Accessing a source set

build.gradle

// Various ways to access the main source set
println sourceSets.main.output.classesDir
println sourceSets['main'].output.classesDir
sourceSets {
    println main.output.classesDir
}
sourceSets {
    main {
        println output.classesDir
    }
}

// Iterate over the source sets
sourceSets.all {
    println name
}

要配置容器，只要用上面的任意一个方法设置源集属性值即可。源集的属性下面会描述。先简单看个例子：

Example 23.4. Configuring the source directories of a source set

build.gradle

sourceSets {
    main {
        java {
            srcDir 'src/java'
        }
        resources {
            srcDir 'src/resources'
        }
    }
}

23.7.1. Source set properties源集属性

下面是一些常用的重要的属性，更多的参见：SourceSet.

Table 23.9. Java plugin - source set properties

Property name	Type	Default value	Description
name	String (read-only)	Not null	The name of the source set, used to identify it.
output	SourceSetOutput (read-only)	Not null	The output files of the source set, containing its compiled classes and resources.
output.classesDir	File	buildDir/classes/name	The directory to generate the classes of this source set into.
output.resourcesDir	File	buildDir/resources/name	The directory to generate the resources of this source set into.
compileClasspath	FileCollection	compileSourceSet configuration.	The classpath to use when compiling the source files of this source set.
runtimeClasspath	FileCollection	output + runtimeSourceSetconfiguration.	The classpath to use when executing the classes of this source set.
java	SourceDirectorySet (read-only)	Not null	The Java source files of this source set. Contains only .java files found in the Java source directories, and excludes all other files.
java.srcDirs	Set<File>. Can set using anything described in Section 16.5, “Specifying a set of input files”.	[projectDir/src/name/java]	The source directories containing the Java source files of this source set.
resources	SourceDirectorySet (read-only)	Not null	The resources of this source set. Contains only resources, and excludes any.java files found in the resource source directories. Other plugins, such as the Groovy plugin, exclude additional types of files from this collection.
resources.srcDirs	Set<File>. Can set using anything described in Section 16.5, “Specifying a set of input files”.	[projectDir/src/name/resources]	The source directories containing the resources of this source set.
allJava	SourceDirectorySet (read-only)	java	All .java files of this source set. Some plugins, such as the Groovy plugin, add additional Java source files to this collection.
allSource	SourceDirectorySet (read-only)	resources + java	All source files of this source set. This include all resource files and all Java source files. Some plugins, such as the Groovy plugin, add additional source files to this collection.

23.7.2. Defining new source sets新建源集

在 sourceSets { } 块中命名就可以创建源集了：

Example 23.5. Defining a source set

build.gradle

sourceSets {
    intTest
}

新建源集后Java插件会给它增加一些依赖配置，见上文： Table 23.6, “Java plugin - source set dependency configurations”. 你可以用这些配置定义源集的编译和运行时依赖。

Example 23.6. Defining source set dependencies

build.gradle

sourceSets {
    intTest
}

dependencies {
    intTestCompile 'junit:junit:4.11'
    intTestRuntime 'org.ow2.asm:asm-all:4.0'
}

Java插件会增加一些汇编任务给源集，见上文 Table 23.2, “Java plugin - source set tasks”. 比如对于 intTest的源集可以通过执行 gradle intTestClasses 来编译

Example 23.7. Compiling a source set

Output of gradle intTestClasses

> gradle intTestClasses
:compileIntTestJava
:processIntTestResources
:intTestClasses

BUILD SUCCESSFUL

Total time: 1 secs

23.8. Javadoc

javadoc任务是Javadoc的实例。它支持核心javadoc选项和标准doclet选项（见 reference documentation )。完整信息参考 CoreJavadocOptions and StandardJavadocDocletOptions.

Table 23.10. Java plugin - Javadoc properties

Task Property	Type	Default Value
classpath	FileCollection	sourceSets.main.output + sourceSets.main.compileClasspath
source	FileTree. Can set using anything described in Section 16.5, “Specifying a set of input files”.	sourceSets.main.allJava
destinationDir	File	docsDir/javadoc
title	String	The name and version of the project

23.9. Clean

clean 任务是Delete的实例，它会把 dir 属性值对应的目录删掉.

Table 23.11. Java plugin - Clean properties

Task Property	Type	Default Value
dir	File	buildDir

23.10. Resources资源

The Java plugin uses the Copy task for resource handling. It adds an instance for each source set in the project. You can find out more about the copy task in Section 16.6, “Copying files”.

Table 23.12. Java plugin - ProcessResources properties

Task Property	Type	Default Value
srcDirs	Object. Can set using anything described in Section 16.5, “Specifying a set of input files”.	sourceSet.resources
destinationDir	File. Can set using anything described in Section 16.1, “Locating files”.	sourceSet.output.resourcesDir

23.11. CompileJava编译

Java插件会给工程中的每个源集增加一个 JavaCompile 类型实例。主要的配置选项如下：

Table 23.13. Java plugin - Compile properties

Task Property	Type	Default Value
classpath	FileCollection	sourceSet.compileClasspath
source	FileTree. Can set using anything described in Section 16.5, “Specifying a set of input files”.	sourceSet.java
destinationDir	File.	sourceSet.output.classesDir

编译任务委托了Ant的 javac 任务，将options.useAnt设为false可以激活Grass的编译集成从而绕过Ant的任务。以后这会成为默认任务。

默认Java的编译工作在Gradle进程中执行。将options.fork 设为 true 会生成单独的进程。在Ant中这样做会减慢编译速度，而在Gradle中相反，Gradle会尽量重复使用编译进程。优先尊重的选项是options.forkOptions

 

23.13. Jar打包

jar任务会生成jar文件，包括了工程的类文件和资源文件。jar文件是 archives 依赖配置的产出，所以依赖工程可以直接引用。如果要把工程上传到库，jar文件会被声明为依赖描述符的一部分。更多请阅读 Section 16.8, “Creating archives” 和 Chapter 51, Publishing artifacts.

23.13.1. Manifest主配置清单

每个jar或war对象都有一个 manifest 属性，值为 Manifest的单独实例。压缩后对应的MANIFEST.MF文件就写入压缩文件中了。

Example 23.15. Customization of MANIFEST.MF

build.gradle

jar {
    manifest {
        attributes("Implementation-Title": "Gradle", "Implementation-Version": version)
    }
}

可以创建 Manifest 的独立实例，这样就可以在jar中共享主配信息了。

Example 23.16. Creating a manifest object.

build.gradle

ext.sharedManifest = manifest {
    attributes("Implementation-Title": "Gradle", "Implementation-Version": version)
}
task fooJar(type: Jar) {
    manifest = project.manifest {
        from sharedManifest
    }
}

 Manifest 对象可以随便合并，可以是文件路径也可以是主配引用等等。

Example 23.17. Separate MANIFEST.MF for a particular archive

build.gradle

task barJar(type: Jar) {
    manifest {
        attributes key1: 'value1'
        from sharedManifest, 'src/config/basemanifest.txt'
        from('src/config/javabasemanifest.txt', 'src/config/libbasemanifest.txt') {
            eachEntry { details ->
                if (details.baseValue != details.mergeValue) {
                    details.value = baseValue
                }
                if (details.key == 'foo') {
                    details.exclude()
                }
            }
        }
    }
}

Manifest会按照from 语句中的顺序进行合并。如果合并中发现相同的值则保持原来的，可以通过增加eachEntry 动作自定义合并行为，在里面要访问 ManifestMergeDetails 的实例。合并并不是立即执行的，而是在生成jar文件或者调用 writeTo 和 effectiveManifest的时候。要把主配写入硬盘很简单：

Example 23.18. Separate MANIFEST.MF for a particular archive

build.gradle

jar.manifest.writeTo("$buildDir/mymanifest.mf")

23.14. Uploading上传

上传请看 Chapter 51, Publishing artifacts.