第 2 部分：建置生命週期

了解 Gradle 建置生命週期以及各階段代表的意義。

在本部分中，您將

了解建置生命週期
註冊和設定兩個工作
執行工作以查看各階段的實際運作

步驟 0. 開始之前

您已在第 1 部分中初始化 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 會決定哪些專案會參與建置，並為每個專案建立一個 Project 實例。
階段 2 - 組態: 在組態階段，會使用建置中所有專案的建置腳本來組態 Project 物件。Gradle 會決定要執行的任務組。
階段 3 - 執行: 在執行階段，Gradle 會執行每個選取的任務。

當 Gradle 被呼叫來執行任務時，生命週期就開始了。讓我們看看實際運作的狀況。

步驟 2. 更新設定檔

將下列程式碼新增到設定檔的最上方

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

將下列程式碼新增到建置腳本的最下方

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 任務

執行您在步驟 3 中註冊和組態的 task1 任務

$ ./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 會執行 `settings.gradle(.kts)` 來決定要建置的專案，並為每個專案建立一個 `Project` 物件。
2	組態：Gradle 會透過執行 `build.gradle(.kts)` 檔案來組態每個專案。它會解析相依性，並建立所有可用任務的相依性圖表。
3	執行：Gradle 會執行命令列上傳遞的任務，以及任何先決條件任務。

重要的是要注意，雖然 task1 已組態和執行，但 task2 卻沒有。這稱為避免任務組態，可以防止不必要的作業。

避免任務組態是指當呼叫 task1 時，Gradle 會避免組態 task2，而且 task1 並不依賴於 task2。

下一步： 多專案建置 >>

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