Gradle构建生命周期

Gradle的核心是基于依赖的编程语言。你可以使用Gradle定义task和task之间的依赖。Gradle保证每个task根据依赖关系决定的次序执行，并且只执行一次。这些task组成一个有向无环图。Gradle将会在执行task 之前构建这个有向无环图。

 

构建阶段

一次Gradle构建由三个阶段组成：

    初始化

          Gradle决定哪些项目将参与这次构建，并为每个项目生成一个Project对象。

    配置

          在这个阶段，Gradle将根据每个项目的构建脚本配置每个Project对象。

    执行

          Gradle根据命令行的输入，在配置阶段生成的task集合中，挑选出将被执行的task，并执行它们。

 

Settings文件

 除了构建脚本外，Gradle定义了一个Settings文件。这个文件的默认名是settings.gradle。Settings文件在配置阶段执行。对于多项目构建，settings.gradle定义了将被构建的项目。对于单项目构建，Settings文件是可选的。

下面是一次Gradle构建执行的例子：

Example: Single project build

settings.gradle

println 'This is executed during the initialization phase.'

build.gradle

println 'This is executed during the configuration phase.'

task configured {
    println 'This is also executed during the configuration phase.'
}

task test {
    doLast {
        println 'This is executed during the execution phase.'
    }
}

task testBoth {
	doFirst {
	  println 'This is executed first during the execution phase.'
	}
	doLast {
	  println 'This is executed last during the execution phase.'
	}
	println 'This is executed during the configuration phase as well.'
}

Output of gradle test testBoth

> gradle test testBoth
This is executed during the initialization phase.

> Configure project :
This is executed during the configuration phase.
This is also executed during the configuration phase.
This is executed during the configuration phase as well.

> Task :test
This is executed during the execution phase.

> Task :testBoth
This is executed first during the execution phase.
This is executed last during the execution phase.

BUILD SUCCESSFUL in 0s
2 actionable tasks: 2 executed

多项目构建

一次多项目构建是指一次Gradle构建执行的过程中构建超过一个项目。

项目位置

一般来说，多项目可以被组织为一个单根数，树的每个结点代表一个项目。大多数情况下，项目的物理存储位置和在树中的位置是一致的，但这个映射也可以在settings.gradle中进行配置。

基于构建脚本生命周期的响应

在构建脚本中可以接收构建过程中的通知，你可以通过实现一个监听器接口或者提供一个闭包来处理这些通知。比如：

allprojects {
    afterEvaluate { project ->
        if (project.hasTests) {
            println "Adding test task to $project"
            project.task('test') {
                doLast {
                    println "Running tests for $project"
                }
            }
        }
    }
}