第 2 部分：建置生命週期

了解 Gradle 建置生命週期以及每個階段代表的意義。

在本節中，您將

了解建置生命週期
註冊和配置兩個工作
執行工作以檢視實際運作中的階段

步驟 0. 開始之前

您已在第 1 部分中初始化您的 Java 應用程式。

步驟 1. 了解建置生命週期

Gradle 建置有三個不同的階段

階段 1 - 初始化: 在初始化階段，Gradle 會決定哪些專案將參與建置，並為每個專案建立一個 Project 實例。
階段 2 - 配置: 在配置階段，會使用建置中所有專案的建置腳本來配置 Project 物件。Gradle 會決定要執行的工作集。
階段 3 - 執行: 在執行階段，Gradle 會執行每個選定的工作。

當調用 Gradle 執行工作時，生命週期便開始。讓我們看看它的實際運作情況。

步驟 2. 更新設定檔

將以下行新增至設定檔的頂部

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')

步驟 3. 更新建置腳本

將以下行新增至建置腳本的底部

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")
    }
}

步驟 4. 執行 Gradle 工作

執行您在步驟 3 中註冊和配置的 task1 工作

$ ./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 執行 `settings.gradle(.kts)` 以決定要建置的專案，並為每個專案建立一個 `Project` 物件。
2	配置：Gradle 透過執行 `build.gradle(.kts)` 檔案來配置每個專案。它會解析相依性並建立所有可用工作的相依性圖。
3	執行：Gradle 執行在命令列上傳遞的工作以及任何先決條件工作。

務必注意，雖然 task1 已配置和執行，但 task2 則否。這稱為工作配置避免，可防止不必要的工作。

工作配置避免是指當呼叫 task1 且 task1 不相依於 task2 時，Gradle 避免配置 task2。

下一步： 多專案建置 >>

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