maven in action

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maven phases and plugins goal

three built-in Lifecycle

  • default
  • clean
  • site

built-in Lifecycle is made up of phases

  • default
    • validate - validate project is correct and all neccessary infomation is avaiable
    • compile
    • test
    • package
    • integration-test
    • verify - run and checks to verify the package is valid and meets quality criteria
    • install - install to local repository
    • deploy - copy the final package to the remote repository for sharing.

a build phase is made up of plugin goals

  • a plugin goal represents a specific task, and bound to those build phases.
  • it’s bound to zero or more build phases
  • mvn clean dependency:copy-dependencies package
  • a phase can also have zero or more goals bound to it. if a build phase has no goals bound to it, it cannot execute.

编写插件的时候，我们会给每一个goal默认绑定一个phase，所以在对应的plugin中，我们或许不需要显式绑定两者

maven core concept: coordinate and dependency

coordinate

  • groupId
  • artifactId
  • version
  • packaging - jar（default）, war
  • classfier - javadoc.jar, sources.jar. cannot defined directly

dependency

  • dependency scope: (compile, test, provided, runtime, system, import), provided(servlet-api) system should with systemPath.
  • transitive dependency
  • dependency mediate (the shortest path, otherwise declartive order in pom)
  • execlusion dependency(groupId & artifactId)

How to look for dependency

mvn dependency:list mvn dependency:tree

mvn dependency:analyze : 标注声明但未使用的依赖或者使用但未声明的依赖(传递依赖)

dependency management

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<dependencyManagement>
    <dependencies>
    ...
    </dependencies>
</dependencyManagement>

防止subModules继承不必要的依赖，同时如果需要，只要在subModule中声明此依赖的groupId, artifactId，无需对应的versionId，因为这是可以继承自parentModule的