Maven中的生命週期的管理使用了COC，以此為中心的pom.xml檔案成為了重中之重，優點是不同專案之間的經驗共享變得更加容易，大家大部分都是可以使用類似的套路，缺點則是靈活性稍微降低以及對於pom.xml細節的學習需要較多時間。Gradle則將這些再次放開，給更多的許可權與開發者，這篇文章來簡單看一下Gradle生命週期管理的一些基礎知識。

gradle構建的階段

gradle的構建分為初期化/配置/執行三個階段：

構建的生命週期

在Maven中大部分專案的生命週期基本使用pom規範中定義的那些即可，而在Gradle中，可以通過Task的定義來定製專案自己所需要的方式。這裡將會把前面的HelloWorld的例子進行簡單的修改，模擬常見的maven專案經常會用到的幾個階段：

程式碼示例

• settings.gradle

liumiaocn:hello liumiao$ cat settings.gradle 
println "[Phase: initialization] : settings executed... "
rootProject.name='helloPorject'
liumiaocn:hello liumiao$ 

• build.gradle
  在gradle中上述的四個階段，可以使用如下4個task來進行模擬:

liumiaocn:hello liumiao$ cat build.gradle 
println "[phase:configuration] build.gradle ..."

task compile() {
  group 'customized'
  description 'compile task'
  println "[phase:configuration] compile"
  doFirst {
    println "[phase:execution] compile :doFirst()"
  }
}

task test {
  group 'customized'
  description 'test task'
  println "[phase:configuration] test"
  doLast {
    println "[phase:execution] test:doLast()"
  }
}

task packaging {
  group 'customized'
  description 'packaging task'
  println "[phase:configuration] packaging"
  doLast {
    println "[phase:execution] packaging:doLast()"
  }
}

task install {
  group 'customized'
  description 'install task'
  println "[phase:configuration] install"
  doFirst {
    println "[phase:execution] install:doFirst()"
  }
  doLast {
    println "[phase:execution] install:doLast()"
  }
}
liumiaocn:hello liumiao$ 
 

執行確認

確認task

liumiaocn:hello liumiao$ gradle tasks
[Phase: initialization] : settings executed... 

> Configure project :
[phase:configuration] build.gradle ...
[phase:configuration] compile
[phase:configuration] test
[phase:configuration] packaging
[phase:configuration] install

> Task :tasks

------------------------------------------------------------
All tasks runnable from root project
------------------------------------------------------------

Build Setup tasks
-----------------
init - Initializes a new Gradle build.
wrapper - Generates Gradle wrapper files.

Customized tasks
----------------
compile - compile task
install - install task
packaging - packaging task
test - test task

Help tasks
----------
buildEnvironment - Displays all buildscript dependencies declared in root project 'helloPorject'.
components - Displays the components produced by root project 'helloPorject'. [incubating]
dependencies - Displays all dependencies declared in root project 'helloPorject'.
dependencyInsight - Displays the insight into a specific dependency in root project 'helloPorject'.
dependentComponents - Displays the dependent components of components in root project 'helloPorject'. [incubating]
help - Displays a help message.
model - Displays the configuration model of root project 'helloPorject'. [incubating]
projects - Displays the sub-projects of root project 'helloPorject'.
properties - Displays the properties of root project 'helloPorject'.
tasks - Displays the tasks runnable from root project 'helloPorject'.

To see all tasks and more detail, run gradle tasks --all

To see more detail about a task, run gradle help --task <task>

BUILD SUCCESSFUL in 0s
1 actionable task: 1 executed
liumiaocn:hello liumiao$ 
 

確認執行

需要注意的上文所講到的生命週期，通過對任務的執行可以看地清清楚楚，無論對哪個任務進行執行，初始化和配置部分的程式碼都會被執行，這點是在使用gradle時需要特別注意的。gradle的groovy或者kotlin的程式碼在什麼階段會被執行，一定要理解和注意。

liumiaocn:hello liumiao$ gradle compile
[Phase: initialization] : settings executed... 

> Configure project :
[phase:configuration] build.gradle ...
[phase:configuration] compile
[phase:configuration] test
[phase:configuration] packaging
[phase:configuration] install

> Task :compile
[phase:execution] compile :doFirst()

BUILD SUCCESSFUL in 0s
1 actionable task: 1 executed
liumiaocn:hello liumiao$

doFrist與doLast

doFirst和doLast都是gradle預留的回撥，在執行階段會被呼叫，兩者的順序是doFirst() -> doLast()

liumiaocn:hello liumiao$ gradle install
[Phase: initialization] : settings executed... 

> Configure project :
[phase:configuration] build.gradle ...
[phase:configuration] compile
[phase:configuration] test
[phase:configuration] packaging
[phase:configuration] install

> Task :install
[phase:execution] install:doFirst()
[phase:execution] install:doLast()

BUILD SUCCESSFUL in 0s
1 actionable task: 1 executed
liumiaocn:hello liumiao$ 

多個任務同時執行

多個任務同時執行，就有點類似maven的動作了

liumiaocn:hello liumiao$ gradle compile test packaging install
[Phase: initialization] : settings executed... 

> Configure project :
[phase:configuration] build.gradle ...
[phase:configuration] compile
[phase:configuration] test
[phase:configuration] packaging
[phase:configuration] install

> Task :compile
[phase:execution] compile :doFirst()

> Task :test
[phase:execution] test:doLast()

> Task :packaging
[phase:execution] packaging:doLast()

> Task :install
[phase:execution] install:doFirst()
[phase:execution] install:doLast()

BUILD SUCCESSFUL in 0s
4 actionable tasks: 4 executed
liumiaocn:hello liumiao$

總結

本系列中的例子的使用方式均是為了解釋Gradle的基礎概念和基本使用方式所整理，實際專案中如何進行最佳實踐的落地，需要自行探索和研究。這篇文章強調的是gradle使用的時候的生命週期的三個階段，一定要多留意這些與maven之類不同的地方。

參考內容

https://docs.gradle.org/current/userguide/build_lifecycle.html