第二部分：构建生命周期

了解 Gradle 构建生命周期以及每个阶段的含义。

在本节中，您将

理解构建生命周期
注册和配置两个 task
运行 task 以查看各个阶段的运行情况

步骤 0. 开始之前

您在第一部分中初始化了 Java 应用程序。

步骤 1. 理解构建生命周期

Gradle 构建有三个不同的阶段

阶段 1 - 初始化: 在初始化阶段，Gradle 确定哪些项目将参与构建，并为每个项目创建一个 Project 实例。
阶段 2 - 配置: 在配置阶段，使用构建中所有项目的构建脚本配置 Project 对象。Gradle 确定要执行的 task 集合。
阶段 3 - 执行: 在执行阶段，Gradle 执行每个选定的 task。

当调用 Gradle 执行 task 时，生命周期开始。让我们看看它的实际运行情况。

步骤 2. 更新 Settings 文件

将以下行添加到 Settings 文件的顶部

settings.gradle.kts

println("SETTINGS FILE: This is executed during the initialization phase")

settings.gradle

println('SETTINGS FILE: This is executed during the initialization phase')

步骤 3. 更新 Build 脚本

将以下行添加到 Build 脚本的底部

app/build.gradle.kts

println("BUILD SCRIPT: This is executed during the configuration phase")

tasks.register("task1"){
    println("REGISTER TASK1: This is executed during the configuration phase")
}

tasks.register("task2"){
    println("REGISTER TASK2: This is executed during the configuration phase")
}

tasks.named("task1"){
    println("NAMED TASK1: This is executed during the configuration phase")
    doFirst {
        println("NAMED TASK1 - doFirst: This is executed during the execution phase")
    }
    doLast {
        println("NAMED TASK1 - doLast: This is executed during the execution phase")
    }
}

tasks.named("task2"){
    println("NAMED TASK2: This is executed during the configuration phase")
    doFirst {
        println("NAMED TASK2 - doFirst: This is executed during the execution phase")
    }
    doLast {
        println("NAMED TASK2 - doLast: This is executed during the execution phase")
    }
}

println("BUILD SCRIPT: This is executed during the configuration phase")

tasks.register("task1") {
    println("REGISTER TASK1: This is executed during the configuration phase")
}

tasks.register("task2") {
    println("REGISTER TASK2: This is executed during the configuration phase")
}

tasks.named("task1") {
    println("NAMED TASK1: This is executed during the configuration phase")
    doFirst {
        println("NAMED TASK1 - doFirst: This is executed during the execution phase")
    }
    doLast {
        println("NAMED TASK1 - doLast: This is executed during the execution phase")
    }
}

tasks.named("task2") {
    println("NAMED TASK2: This is executed during the configuration phase")
    doFirst {
        println("NAMED TASK2 - doFirst: This is executed during the execution phase")
    }
    doLast {
        println("NAMED TASK2 - doLast: This is executed during the execution phase")
    }
}

步骤 4. 运行 Gradle Task

运行您在步骤 3 中注册和配置的 task1 task

$ ./gradlew task1

SETTINGS FILE: This is executed during the initialization phase     (1)

> Configure project :app
BUILD SCRIPT: This is executed during the configuration phase       (2)
REGISTER TASK1: This is executed during the configuration phase     (2)
NAMED TASK1: This is executed during the configuration phase        (2)

> Task :app:task1
NAMED TASK1 - doFirst: This is executed during the execution phase  (3)
NAMED TASK1 - doLast: This is executed during the execution phase   (3)

BUILD SUCCESSFUL in 25s
5 actionable tasks: 3 executed, 2 up-to-date

1	初始化：Gradle 执行 `settings.gradle(.kts)` 以确定要构建的项目，并为每个项目创建一个 `Project` 对象。
2	配置：Gradle 通过执行 `build.gradle(.kts)` 文件来配置每个项目。它解析依赖项并创建所有可用 task 的依赖图。
3	执行：Gradle 执行在命令行上传递的 task 以及任何先决 task。

重要的是要注意，虽然 task1 已配置和执行，但 task2 没有。这称为task 配置避免，可以防止不必要的工作。

Task 配置避免是指当调用 task1 且 task1 不依赖于 task2 时，Gradle 避免配置 task2。

下一步： 多项目构建 >>

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