56.1.1. 配置和执行

由于每个项目都在执行阶段之前配置，所以也能做到配置注入功能以及访问整个项目模型。然而，在一个非常大的多项目构建里，这种方法可能不是最有效的。存在着一些项目，它们在层次结构上有上百个的子项目。对于巨大的项目，这个配置时间就会变得非常可观。可伸缩性是 Gradle 的一项重要要求。因此，从 1.4 版本起，新引入了一个孵化功能“按需配置”。

按需配置模式尝试只配置所请求的任务相关的项目。这种方式，大大提高了大型多项目构建的配置时间。长远来看，这种模式将成为默认模式，可能会是 Gradle 构建执行的唯一模式。配置需求功能正在孵化中，所以还无法保证每次的构建都能正确。对于解耦的多项目构建，这个功能应该会运行得很好（第 56.9 节，“解耦项目”）。在按需配置的模式下项目会如下配置︰

想尝试这一新功能？要在每次构建时都按需配置，请参阅第 20.1 节，“通过 gradle.properties配置构建环境”。只对指定的构建按需配置，请参见附录 D， Gradle 命令行。

56.1.2. 定义共同行为

示例 56.1. 多项目树- water & bluewhale 项目

water/build.gradlesettings.gradlebluewhale/

include 'bluewhale'

示例 56.2. water（父）项目的构建脚本

Closure cl = { task -> println "I'm $task.project.name" }
task hello << cl
project(':bluewhale') {task hello << cl
}

> gradle -q hello
I'm water
I'm bluewhale

示例 56.3. 多项目树- water & bluewhale & krill 项目

water/build.gradlesettings.gradlebluewhale/krill/

include 'bluewhale', 'krill'

示例 56.4. Water项目构建脚本

allprojects {task hello << { task -> println "I'm $task.project.name" }
}

> gradle -q hello
I'm water
I'm bluewhale
I'm krill

56.2.1. 定义共同行为

示例 56.5. 定义所有项目以及子项目的共同行为

allprojects {task hello << {task -> println "I'm $task.project.name" }
}
subprojects {hello << {println "- I depend on water"}
}

> gradle -q hello
I'm water
I'm bluewhale
- I depend on water
I'm krill
- I depend on water

56.2.2. 添加特定的行为

示例 56.6. 为特定项目定义特定行为

allprojects {task hello << {task -> println "I'm $task.project.name" }
}
subprojects {hello << {println "- I depend on water"}
}
project(':bluewhale').hello << {println "- I'm the largest animal that has ever lived on this planet."
}

> gradle -q hello
I'm water
I'm bluewhale
- I depend on water
- I'm the largest animal that has ever lived on this planet.
I'm krill
- I depend on water

示例 56.7. 为krill项目定义特定的行为

water/build.gradlesettings.gradlebluewhale/build.gradlekrill/build.gradle

include 'bluewhale', 'krill'

hello.doLast { println "- I'm the largest animal that has ever lived on this planet." }

hello.doLast {println "- The weight of my species in summer is twice as heavy as all human beings."
}

allprojects {task hello << {task -> println "I'm $task.project.name" }
}
subprojects {hello << {println "- I depend on water"}
}

> gradle -q hello
I'm water
I'm bluewhale
- I depend on water
- I'm the largest animal that has ever lived on this planet.
I'm krill
- I depend on water
- The weight of my species in summer is twice as heavy as all human beings.

56.2.3. 项目筛选

water/build.gradlesettings.gradlebluewhale/build.gradlekrill/build.gradletropicalFish/

include 'bluewhale', 'krill', 'tropicalFish'

allprojects {task hello << {task -> println "I'm $task.project.name" }
}
subprojects {hello << {println "- I depend on water"}
}
configure(subprojects.findAll {it.name != 'tropicalFish'}) {hello << {println '- I love to spend time in the arctic waters.'}
}

> gradle -q hello
I'm water
I'm bluewhale
- I depend on water
- I love to spend time in the arctic waters.
- I'm the largest animal that has ever lived on this planet.
I'm krill
- I depend on water
- I love to spend time in the arctic waters.
- The weight of my species in summer is twice as heavy as all human beings.
I'm tropicalFish
- I depend on water

configure()方法接受一个list作为参数，并将配置应用到这个list里的项目。

我们可以选择使用project的名称来筛选，或者是使用额外的项目属性。（有关额外属性的更多信息，请参见第 13.4.2 节，“额外属性”。）

water/build.gradlesettings.gradlebluewhale/build.gradlekrill/build.gradletropicalFish/build.gradle

include 'bluewhale', 'krill', 'tropicalFish'

ext.arctic = true
hello.doLast { println "- I'm the largest animal that has ever lived on this planet." }

ext.arctic = true
hello.doLast {println "- The weight of my species in summer is twice as heavy as all human beings."
}

ext.arctic = false

allprojects {task hello << {task -> println "I'm $task.project.name" }
}
subprojects {hello {doLast {println "- I depend on water"}afterEvaluate { Project project ->if (project.arctic) { doLast {println '- I love to spend time in the arctic waters.' }}}}
}

> gradle -q hello
I'm water
I'm bluewhale
- I depend on water
- I'm the largest animal that has ever lived on this planet.
- I love to spend time in the arctic waters.
I'm krill
- I depend on water
- The weight of my species in summer is twice as heavy as all human beings.
- I love to spend time in the arctic waters.
I'm tropicalFish
- I depend on water

在这个water项目的构建文件中，我们使用了一个afterEvaluate通知。这意味着我们所传的闭包在子项目的构建脚本评估之后才被评估。由于arctic属性被设置在那些构建脚本中，我们不得不这样做。在 第 56.6 节， “依赖——哪些依赖”，你可以看到更多关于这个主题的内容。

gradle -q hello的输出结果

> gradle -q hello
I'm bluewhale
- I depend on water
- I'm the largest animal that has ever lived on this planet.
- I love to spend time in the arctic waters.

bluewhale/build.gradle

ext.arctic = true
hello << { println "- I'm the largest animal that has ever lived on this planet." }task distanceToIceberg << {println '20 nautical miles'
}

krill/build.gradle

ext.arctic = true
hello << { println "- The weight of my species in summer is twice as heavy as all human beings." }task distanceToIceberg << {println '5 nautical miles'
}

gradle -q distanceToIceberg的输出结果

> gradle -q distanceToIceberg
20 nautical miles
5 nautical miles

gradle distanceToIceberg的输出结果

> gradle distanceToIceberg
:bluewhale:distanceToIceberg
20 nautical miles
:krill:distanceToIceberg
5 nautical milesBUILD SUCCESSFULTotal time: 1 secs

gradle -q :hello :krill:hello hello的输出结果

> gradle -q :hello :krill:hello hello
I'm water
I'm krill
- I depend on water
- The weight of my species in summer is twice as heavy as all human beings.
- I love to spend time in the arctic waters.
I'm tropicalFish
- I depend on water

56.6.1. 执行依赖

messages/settings.gradleconsumer/build.gradleproducer/build.gradle

include 'consumer', 'producer'

task action << {println("Consuming message: ${rootProject.producerMessage}")
}

task action << {println "Producing message:"rootProject.producerMessage = 'Watch the order of execution.'
}

> gradle -q action
Consuming message: null
Producing message:

它并没有成功。如果没有别的定义，Gradle 会按字母数字顺序执行该任务。因此:consumer:action会在:producer:action之前执行。让我们试着用一个技巧解决这个问题，并将生产者项目命名为aProducer。

messages/settings.gradleaProducer/build.gradleconsumer/build.gradle

include 'consumer', 'aProducer'

task action << {println "Producing message:"rootProject.producerMessage = 'Watch the order of execution.'
}

task action << {println("Consuming message: ${rootProject.producerMessage}")
}

> gradle -q action
Producing message:
Consuming message: Watch the order of execution.

现在我们来看这个技巧。我们简单地切换到consumer目录并执行构建。

> gradle -q action
Consuming message: null

对于 Gradle 而言，这两个action任务不相关。如果你从 messages 项目执行构建，Gradle 会执行它们两个，因为他们具有相同的名称，并且它们在该层次结构下。在上一个例子中只有一个action是在这个层次结构下，因此它是唯一一个被执行的任务。我们需要比这种技巧更好的实现。

messages/settings.gradleconsumer/build.gradleproducer/build.gradle

include 'consumer', 'producer'

task action(dependsOn: ":producer:action") << {println("Consuming message: ${rootProject.producerMessage}")
}

task action << {println "Producing message:"rootProject.producerMessage = 'Watch the order of execution.'
}

> gradle -q action
Producing message:
Consuming message: Watch the order of execution.

从consumer目录运行如下：

> gradle -q action
Producing message:
Consuming message: Watch the order of execution.

我们现在声明了consumer项目的action任务对producer项目上的action任务有执行依赖。

当然，在不同项目之间的任务依赖并不限于具有相同名称的任务。让我们改变我们的任务的命名，执行构建。

task consume(dependsOn: ':producer:produce') << {println("Consuming message: ${rootProject.producerMessage}")
}

task produce << {println "Producing message:"rootProject.producerMessage = 'Watch the order of execution.'
}

-> gradle -q action
Producing message:
Consuming message: Watch the order of execution.

56.6.2. 配置时依赖

示例 56.20. 配置时依赖

message = rootProject.producerMessagetask consume << {println("Consuming message: " + message)
}

rootProject.producerMessage = 'Watch the order of evaluation.'

> gradle -q consume
Consuming message: null

示例 56.21. 配置时依赖——evaluationDependsOn

evaluationDependsOn(':producer')message = rootProject.producerMessagetask consume << {println("Consuming message: " + message)
}

> gradle -q consume
Consuming message: Watch the order of evaluation.

示例 56.22. 配置时依赖

task consume << {println("Consuming message: ${rootProject.producerMessage}")
}

> gradle -q consume
Consuming message: Watch the order of evaluation.

56.6.3. 实际生活中的例子

示例 56.23. 依赖——真实生活中的例子——跨项目配置

webDist/settings.gradlebuild.gradledate/src/main/java/org/gradle/sample/DateServlet.javahello/src/main/java/org/gradle/sample/HelloServlet.java

include 'date', 'hello'

allprojects {apply plugin: 'java'group = 'org.gradle.sample'version = '1.0'
}subprojects {apply plugin: 'war'repositories {mavenCentral()}dependencies {compile "javax.servlet:servlet-api:2.5"}
}task explodedDist(dependsOn: assemble) << {File explodedDist = mkdir("$buildDir/explodedDist")subprojects.each {project ->project.tasks.withType(Jar).each {archiveTask ->copy {from archiveTask.archivePathinto explodedDist}}}
}

构建布局

java/settings.gradlebuild.gradleapi/src/main/java/org/gradle/sample/api/Person.javaapiImpl/PersonImpl.javaservices/personService/src/main/java/org/gradle/sample/services/PersonService.javatest/java/org/gradle/sample/services/PersonServiceTest.javashared/src/main/java/org/gradle/sample/shared/Helper.java

settings.gradle

include 'api', 'shared', 'services:personService'

build.gradle

subprojects {apply plugin: 'java'group = 'org.gradle.sample'version = '1.0'repositories {mavenCentral()}dependencies {testCompile "junit:junit:4.11"}
}project(':api') {dependencies {compile project(':shared')}
}project(':services:personService') {dependencies {compile project(':shared'), project(':api')}
}

build.gradle

subprojects {apply plugin: 'java'group = 'org.gradle.sample'version = '1.0'
}project(':api') {configurations {spi}dependencies {compile project(':shared')}task spiJar(type: Jar) {baseName = 'api-spi'dependsOn classesfrom sourceSets.main.outputinclude('org/gradle/sample/api/**')}artifacts {spi spiJar}
}project(':services:personService') {dependencies {compile project(':shared')compile project(path: ':api', configuration: 'spi')testCompile "junit:junit:4.11", project(':api')}
}

56.7.1. 禁止依赖项目的构建

gradle :api:build的输出结果

> gradle :api:build
:shared:compileJava
:shared:processResources
:shared:classes
:shared:jar
:api:compileJava
:api:processResources
:api:classes
:api:jar
:api:assemble
:api:compileTestJava
:api:processTestResources
:api:testClasses
:api:test
:api:check
:api:buildBUILD SUCCESSFULTotal time: 1 secs

gradle :api:build的输出结果

-> gradle :api:build
:shared:compileJava
:shared:processResources
:shared:classes
:shared:jar
:api:compileJava
:api:processResources
:api:classes
:api:jar
:api:assemble
:api:compileTestJava
:api:processTestResources
:api:testClasses
:api:test
:api:check
:api:buildBUILD SUCCESSFULTotal time: 1 secs

gradle: api:buildNeeded 的输出结果

> gradle :api:buildNeeded
:shared:compileJava
:shared:processResources
:shared:classes
:shared:jar
:api:compileJava
:api:processResources
:api:classes
:api:jar
:api:assemble
:api:compileTestJava
:api:processTestResources
:api:testClasses
:api:test
:api:check
:api:build
:shared:assemble
:shared:compileTestJava
:shared:processTestResources
:shared:testClasses
:shared:test
:shared:check
:shared:build
:shared:buildNeeded
:api:buildNeededBUILD SUCCESSFULTotal time: 1 secs

gradle :api:buildDependents的输出结果

> gradle :api:buildDependents
:shared:compileJava
:shared:processResources
:shared:classes
:shared:jar
:api:compileJava
:api:processResources
:api:classes
:api:jar
:api:assemble
:api:compileTestJava
:api:processTestResources
:api:testClasses
:api:test
:api:check
:api:build
:services:personService:compileJava
:services:personService:processResources
:services:personService:classes
:services:personService:jar
:services:personService:assemble
:services:personService:compileTestJava
:services:personService:processTestResources
:services:personService:testClasses
:services:personService:test
:services:personService:check
:services:personService:build
:services:personService:buildDependents
:api:buildDependentsBUILD SUCCESSFULTotal time: 1 secs