Maven-07: 插件的自定义绑定

除了内置绑定以外，用户还能够自己选择将某个插件目标绑定到生命周期的某个阶段上，这种自定义绑定方式能让Maven项目在构建过程中执行更多更富特色的任务。

一个常见的例子是创建项目的源码jar包。内置的插件绑定关系中没有涉及这一任务，因此需要用户自行配置。maven-source-plugin可以帮助我们完成该任务，它的jar-no-fork目标能够将项目的主代码打包成jar文件，可以将其绑定到default生命周期的verify阶段上，在执行完集成测试后和安装构件之前创建源码jar包。具体配置见下：

         <plugin>
              <groupId>org.apache.maven.plugins</groupId>
              <artifactId>maven-source-plugin</artifactId>
              <version>2.1.1</version>
              <executions>
                  <execution>
                      <id>attach-sources</id>
                      <phase>verify</phase>
                      <goals>
                          <goal>jar-no-fork</goal>
                      </goals>
                  </execution>
              </executions>
          </plugin>

上述配置中，除了基本的插件坐标声明外，还有插件执行配置，executions下每个execution子元素可以用来配置执行一个任务。

pom.xml:

<project xmlns="http://maven.apache.org/POM/4.0.0" 
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 
    http://maven.apache.org/xsd/maven-4.0.0.xsd">
  <modelVersion>4.0.0</modelVersion>
  <groupId>com.amaze</groupId>
  <artifactId>customBindings</artifactId>
  <version>0.0.1-SNAPSHOT</version>
  <name>Maven Custom Binding Plugin</name>
  
  <build>
      <plugins>
          <plugin>
              <groupId>org.apache.maven.plugins</groupId>
              <artifactId>maven-source-plugin</artifactId>
              <version>2.1.1</version>
              <executions>
                  <execution>
                      <id>attach-sources</id>
                      <phase>verify</phase>
                      <goals>
                          <goal>jar-no-fork</goal>
                      </goals>
                  </execution>
              </executions>
          </plugin>
          
          <plugin>
              <groupId>org.apache.maven.plugins</groupId>
              <artifactId>maven-compiler-plugin</artifactId>
              <configuration>
                  <source>1.6</source>
                  <target>1.6</target>
              </configuration>
          </plugin>
      </plugins>
  </build>
</project>

HelloWorld.java:

package com.amaze.custombindings;

public class HelloWorld {

    public String sayHello(String name){
        return "Hello "+name;
    }
}

命令行中到项目根目录下执行mvn clean verify命令，完成后project_home\target下会生成两个jar：

有很多插件的目标在编写时已经定义了默认绑定阶段，在上述配置中删除<pahse>verify</phase>一行，构建仍然可以顺利完成。可以使用maven-help-plugin查看插件详细信息，了解插件目标的默认绑定阶段，运行命令如下：

因为输出内容比较多，屏幕放不下，我们将其生成txt文件：

[INFO] Scanning for projects...
[INFO]                                                                         
[INFO] ------------------------------------------------------------------------
[INFO] Building Maven Stub Project (No POM) 1
[INFO] ------------------------------------------------------------------------
[INFO] 
[INFO] --- maven-help-plugin:2.2:describe (default-cli) @ standalone-pom ---
[INFO] org.apache.maven.plugins:maven-source-plugin:2.1.1

Name: Maven Source Plugin
Description: The Maven 2 Source Plugin creates a JAR archive of the source
  files of the current project.
Group Id: org.apache.maven.plugins
Artifact Id: maven-source-plugin
Version: 2.1.1
Goal Prefix: source

This plugin has 6 goals:

source:aggregate
  Description: Aggregate sources for all modules in an aggregator project.
  Implementation: org.apache.maven.plugin.source.AggregatorSourceJarMojo
  Language: java
  Bound to phase: package
  Before this mojo executes, it will call:
    Phase: 'generate-sources'

  Available parameters:

    archive
      The archive configuration to use. See Maven Archiver Reference.

    attach (Default: true)
      User property: attach
      Specifies whether or not to attach the artifact to the project

    excludeResources (Default: false)
      User property: source.excludeResources
      Specifies whether or not to exclude resources from the sources-jar. This
      can be convenient if your project includes large resources, such as
      images, and you don't want to include them in the sources-jar.

    excludes
      List of files to exclude. Specified as fileset patterns which are
      relative to the input directory whose contents is being packaged into the
      JAR.

    finalName (Default: ${project.build.finalName})
      The filename to be used for the generated archive file. For the
      source:jar goal, '-sources' is appended to this filename. For the
      source:test-jar goal, '-test-sources' is appended.

    forceCreation (Default: false)
      User property: source.forceCreation
      Whether creating the archive should be forced. If set to true, the jar
      will always be created. If set to false, the jar will only be created
      when the sources are newer than the jar.

    includePom (Default: false)
      User property: source.includePom
      Specifies whether or not to include the POM file in the sources-jar.

    includes
      List of files to include. Specified as fileset patterns which are
      relative to the input directory whose contents is being packaged into the
      JAR.

    outputDirectory (Default: ${project.build.directory})
      The directory where the generated archive file will be put.

    useDefaultExcludes (Default: true)
      Exclude commonly excluded files such as SCM configuration. These are
      defined in the plexus FileUtils.getDefaultExcludes()

    useDefaultManifestFile (Default: false)
      Set this to true to enable the use of the defaultManifestFile.

source:help
  Description: Display help information on maven-source-plugin.
    Call
     mvn source:help -Ddetail=true -Dgoal=<goal-name>
    to display parameter details.
  Implementation: org.apache.maven.plugin.source.HelpMojo
  Language: java

  Available parameters:

    detail (Default: false)
      User property: detail
      If true, display all settable properties for each goal.

    goal
      User property: goal
      The name of the goal for which to show help. If unspecified, all goals
      will be displayed.

    indentSize (Default: 2)
      User property: indentSize
      The number of spaces per indentation level, should be positive.

    lineLength (Default: 80)
      User property: lineLength
      The maximum length of a display line, should be positive.

source:jar
  Description: This plugin bundles all the sources into a jar archive.
  Implementation: org.apache.maven.plugin.source.SourceJarMojo
  Language: java
  Bound to phase: package
  Before this mojo executes, it will call:
    Phase: 'generate-sources'

  Available parameters:

    archive
      The archive configuration to use. See Maven Archiver Reference.

    attach (Default: true)
      User property: attach
      Specifies whether or not to attach the artifact to the project

    excludeResources (Default: false)
      User property: source.excludeResources
      Specifies whether or not to exclude resources from the sources-jar. This
      can be convenient if your project includes large resources, such as
      images, and you don't want to include them in the sources-jar.

    excludes
      List of files to exclude. Specified as fileset patterns which are
      relative to the input directory whose contents is being packaged into the
      JAR.

    finalName (Default: ${project.build.finalName})
      The filename to be used for the generated archive file. For the
      source:jar goal, '-sources' is appended to this filename. For the
      source:test-jar goal, '-test-sources' is appended.

    forceCreation (Default: false)
      User property: source.forceCreation
      Whether creating the archive should be forced. If set to true, the jar
      will always be created. If set to false, the jar will only be created
      when the sources are newer than the jar.

    includePom (Default: false)
      User property: source.includePom
      Specifies whether or not to include the POM file in the sources-jar.

    includes
      List of files to include. Specified as fileset patterns which are
      relative to the input directory whose contents is being packaged into the
      JAR.

    outputDirectory (Default: ${project.build.directory})
      The directory where the generated archive file will be put.

    useDefaultExcludes (Default: true)
      Exclude commonly excluded files such as SCM configuration. These are
      defined in the plexus FileUtils.getDefaultExcludes()

    useDefaultManifestFile (Default: false)
      Set this to true to enable the use of the defaultManifestFile.

source:jar-no-fork
  Description: This goal bundles all the sources into a jar archive. This
    goal functions the same as the jar goal but does not fork the build and is
    suitable for attaching to the build lifecycle.
  Implementation: org.apache.maven.plugin.source.SourceJarNoForkMojo
  Language: java
  Bound to phase: package

  Available parameters:

    archive
      The archive configuration to use. See Maven Archiver Reference.

    attach (Default: true)
      User property: attach
      Specifies whether or not to attach the artifact to the project

    excludeResources (Default: false)
      User property: source.excludeResources
      Specifies whether or not to exclude resources from the sources-jar. This
      can be convenient if your project includes large resources, such as
      images, and you don't want to include them in the sources-jar.

    excludes
      List of files to exclude. Specified as fileset patterns which are
      relative to the input directory whose contents is being packaged into the
      JAR.

    finalName (Default: ${project.build.finalName})
      The filename to be used for the generated archive file. For the
      source:jar goal, '-sources' is appended to this filename. For the
      source:test-jar goal, '-test-sources' is appended.

    forceCreation (Default: false)
      User property: source.forceCreation
      Whether creating the archive should be forced. If set to true, the jar
      will always be created. If set to false, the jar will only be created
      when the sources are newer than the jar.

    includePom (Default: false)
      User property: source.includePom
      Specifies whether or not to include the POM file in the sources-jar.

    includes
      List of files to include. Specified as fileset patterns which are
      relative to the input directory whose contents is being packaged into the
      JAR.

    outputDirectory (Default: ${project.build.directory})
      The directory where the generated archive file will be put.

    useDefaultExcludes (Default: true)
      Exclude commonly excluded files such as SCM configuration. These are
      defined in the plexus FileUtils.getDefaultExcludes()

    useDefaultManifestFile (Default: false)
      Set this to true to enable the use of the defaultManifestFile.

source:test-jar
  Description: This plugin bundles all the test sources into a jar archive.
  Implementation: org.apache.maven.plugin.source.TestSourceJarMojo
  Language: java
  Bound to phase: package
  Before this mojo executes, it will call:
    Phase: 'generate-sources'

  Available parameters:

    archive
      The archive configuration to use. See Maven Archiver Reference.

    attach (Default: true)
      User property: attach
      Specifies whether or not to attach the artifact to the project

    excludeResources (Default: false)
      User property: source.excludeResources
      Specifies whether or not to exclude resources from the sources-jar. This
      can be convenient if your project includes large resources, such as
      images, and you don't want to include them in the sources-jar.

    excludes
      List of files to exclude. Specified as fileset patterns which are
      relative to the input directory whose contents is being packaged into the
      JAR.

    finalName (Default: ${project.build.finalName})
      The filename to be used for the generated archive file. For the
      source:jar goal, '-sources' is appended to this filename. For the
      source:test-jar goal, '-test-sources' is appended.

    forceCreation (Default: false)
      User property: source.forceCreation
      Whether creating the archive should be forced. If set to true, the jar
      will always be created. If set to false, the jar will only be created
      when the sources are newer than the jar.

    includePom (Default: false)
      User property: source.includePom
      Specifies whether or not to include the POM file in the sources-jar.

    includes
      List of files to include. Specified as fileset patterns which are
      relative to the input directory whose contents is being packaged into the
      JAR.

    outputDirectory (Default: ${project.build.directory})
      The directory where the generated archive file will be put.

    useDefaultExcludes (Default: true)
      Exclude commonly excluded files such as SCM configuration. These are
      defined in the plexus FileUtils.getDefaultExcludes()

    useDefaultManifestFile (Default: false)
      Set this to true to enable the use of the defaultManifestFile.

source:test-jar-no-fork
  Description: This goal bundles all the test sources into a jar archive.
    This goal functions the same as the test-jar goal but does not fork the
    build, and is suitable for attaching to the build lifecycle.
  Implementation: org.apache.maven.plugin.source.TestSourceJarNoForkMojo
  Language: java
  Bound to phase: package

  Available parameters:

    archive
      The archive configuration to use. See Maven Archiver Reference.

    attach (Default: true)
      User property: attach
      Specifies whether or not to attach the artifact to the project

    excludeResources (Default: false)
      User property: source.excludeResources
      Specifies whether or not to exclude resources from the sources-jar. This
      can be convenient if your project includes large resources, such as
      images, and you don't want to include them in the sources-jar.

    excludes
      List of files to exclude. Specified as fileset patterns which are
      relative to the input directory whose contents is being packaged into the
      JAR.

    finalName (Default: ${project.build.finalName})
      The filename to be used for the generated archive file. For the
      source:jar goal, '-sources' is appended to this filename. For the
      source:test-jar goal, '-test-sources' is appended.

    forceCreation (Default: false)
      User property: source.forceCreation
      Whether creating the archive should be forced. If set to true, the jar
      will always be created. If set to false, the jar will only be created
      when the sources are newer than the jar.

    includePom (Default: false)
      User property: source.includePom
      Specifies whether or not to include the POM file in the sources-jar.

    includes
      List of files to include. Specified as fileset patterns which are
      relative to the input directory whose contents is being packaged into the
      JAR.

    outputDirectory (Default: ${project.build.directory})
      The directory where the generated archive file will be put.

    useDefaultExcludes (Default: true)
      Exclude commonly excluded files such as SCM configuration. These are
      defined in the plexus FileUtils.getDefaultExcludes()

    useDefaultManifestFile (Default: false)
      Set this to true to enable the use of the defaultManifestFile.


[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESS
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 2.837 s
[INFO] Finished at: 2015-11-18T11:58:14+08:00
[INFO] Final Memory: 7M/96M
[INFO] ------------------------------------------------------------------------

我们知道，当插件目标被绑定到不同的生命周期阶段的时候，其执行顺序会由生命周期阶段的先后顺序决定。如果多个目标被绑定到同一个阶段，它们的执行顺序会是怎样？答案很简单，当多个插件目标绑定到同一个阶段的时候，这些插件声明的先后顺序决定了目标的执行顺序。