Maven: Basic Concepts（Lifecycle, Phase, Goal)

Lifecycle / Phase / Goal

A build lifecycle is made up of phases.
lifecycle將各phase有順序性的串連起來，所以當你指定執行一個phase時，maven將會執行排在其之前的所有phases.

A phase is made up of goals.
一個Phase可以綁定多個Goals，但一般只有預設的一個Goal會被執行，所以要執行其他的Goal時，
必需明白指出所要執行Goal。一般來說是以plugin:goal來表示，例如compile:test-compile

說明下上面兩者的差別，例如test-compile這個phase，實際上是要執行compiler:testCompile，但是分別執行的結果如下

mvn test-compile

>$ mvn test-compile
[INFO] Scanning for projects...
[INFO] ------------------------------------------------------------------------
[INFO] Building Maven
[INFO]    task-segment: [test-compile]
[INFO] ------------------------------------------------------------------------
[INFO] [resources:resources {execution: default-resources}]
[WARNING] Using platform encoding (UTF-8 actually) to copy filtered resources, i.e. build is platform dependent!
[INFO] skip non existing resourceDirectory /Users/elliot/Documents/workspacetesting/test/src/main/resources
[INFO] [compiler:compile {execution: default-compile}]
[INFO] No sources to compile
[INFO] [resources:testResources {execution: default-testResources}]
[WARNING] Using platform encoding (UTF-8 actually) to copy filtered resources, i.e. build is platform dependent!
[INFO] skip non existing resourceDirectory /Users/elliot/Documents/workspacetesting/test/src/test/resources
[INFO] [compiler:testCompile {execution: default-testCompile}]
[INFO] No sources to compile
[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESSFUL
[INFO] ------------------------------------------------------------------------

maven認出test-compile是一個Phase，所以執行了排在test-compile之前的Phase，
如generate-resources、compile、generate-test-resource，最後在執行完test-compile
（其實就是compiler:testCompile)後結束。

mvn compiler:testCompile

>$ mvn compiler:testCompile
[INFO] Scanning for projects...
[INFO] ------------------------------------------------------------------------
[INFO] Building Maven
[INFO]    task-segment: [compiler:testCompile]
[INFO] ------------------------------------------------------------------------
[INFO] [compiler:testCompile {execution: default-cli}]
[INFO] No sources to compile
[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESSFUL
[INFO] ------------------------------------------------------------------------

Maven認出這是一個Goal所以只執行了compiler:testCompile就結束，並未執行其他的Goals。

Maven預設了三個Lifecycle ，各包涵了下列Phases.

1. Clean Lifecycle
   • pre-clean
   • clean
   • post-clean
2. Default Lifecycle
   • validate
   • initialize
   • generate-sources
   • process-sources
   • generate-resources
   • process-resources
   • compile
   • process-classes
   • generate-test-sources
   • process-test-sources
   • process-test-resources
   • test-compile
   • process-test-classes
   • test
   • prepare-package
   • package
   • pre-integration-test
   • integration-test
   • post-integration-test
   • verify
   • install
   • deploy
3. Site Lifecycle
   • pre-site
   • site
   • post-site
   • site-deploy

並不是所有的Phase都需要被執行，例如validate，在一般的情形下，單獨執行這個Phase會出現
No goals needed for project - skipping而結束。
而有些Phase會因設定的不同而執行不同的Goal，
例如package，會因為你所設的packaging而執行war:war或jar:jar等不同的Goal。