Maven Super POM

所有maven模块（项目）的POM（Project Object Model，项目对象模型）都隐式的继承了Super POM。Super POM中定义了一组标准的配置变量。maven模块（项目）的POM会自动继承这些配置变量，你可以在maven模块（项目）的POM文件中直接使用它们，或者通过重新声明以覆盖它们。

环境

Windows 10 Maven 3.5.4

倘若Maven安装的目录用{MAVEN_HOME}来表示，那么，Maven Super POM文件所在的路径为：{MAVEN_HOME}/lib/maven-model-builder-3.5.4.jar/org/apache/maven/model/pom-4.0.0.xml

<?xml version="1.0" encoding="UTF-8"?>

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    http://www.apache.org/licenses/LICENSE-2.0

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<!-- START SNIPPET: superpom -->
<project>
  <modelVersion>4.0.0</modelVersion>

  <repositories>
    <repository>
      <id>central</id>
      <name>Central Repository</name>
      <url>https://repo.maven.apache.org/maven2</url>
      <layout>default</layout>
      <snapshots>
        <enabled>false</enabled>
      </snapshots>
    </repository>
  </repositories>

  <pluginRepositories>
    <pluginRepository>
      <id>central</id>
      <name>Central Repository</name>
      <url>https://repo.maven.apache.org/maven2</url>
      <layout>default</layout>
      <snapshots>
        <enabled>false</enabled>
      </snapshots>
      <releases>
        <updatePolicy>never</updatePolicy>
      </releases>
    </pluginRepository>
  </pluginRepositories>

  <build>
    <directory>${project.basedir}/target</directory>
    <outputDirectory>${project.build.directory}/classes</outputDirectory>
    <finalName>${project.artifactId}-${project.version}</finalName>
    <testOutputDirectory>${project.build.directory}/test-classes</testOutputDirectory>
    <sourceDirectory>${project.basedir}/src/main/java</sourceDirectory>
    <scriptSourceDirectory>${project.basedir}/src/main/scripts</scriptSourceDirectory>
    <testSourceDirectory>${project.basedir}/src/test/java</testSourceDirectory>
    <resources>
      <resource>
        <directory>${project.basedir}/src/main/resources</directory>
      </resource>
    </resources>
    <testResources>
      <testResource>
        <directory>${project.basedir}/src/test/resources</directory>
      </testResource>
    </testResources>
    <pluginManagement>
      <!-- NOTE: These plugins will be removed from future versions of the super POM -->
      <!-- They are kept for the moment as they are very unlikely to conflict with lifecycle mappings (MNG-4453) -->
      <plugins>
        <plugin>
          <artifactId>maven-antrun-plugin</artifactId>
          <version>1.3</version>
        </plugin>
        <plugin>
          <artifactId>maven-assembly-plugin</artifactId>
          <version>2.2-beta-5</version>
        </plugin>
        <plugin>
          <artifactId>maven-dependency-plugin</artifactId>
          <version>2.8</version>
        </plugin>
        <plugin>
          <artifactId>maven-release-plugin</artifactId>
          <version>2.5.3</version>
        </plugin>
      </plugins>
    </pluginManagement>
  </build>

  <reporting>
    <outputDirectory>${project.build.directory}/site</outputDirectory>
  </reporting>

  <profiles>
    <!-- NOTE: The release profile will be removed from future versions of the super POM -->
    <profile>
      <id>release-profile</id>

      <activation>
        <property>
          <name>performRelease</name>
          <value>true</value>
        </property>
      </activation>

      <build>
        <plugins>
          <plugin>
            <inherited>true</inherited>
            <artifactId>maven-source-plugin</artifactId>
            <executions>
              <execution>
                <id>attach-sources</id>
                <goals>
                  <goal>jar-no-fork</goal>
                </goals>
              </execution>
            </executions>
          </plugin>
          <plugin>
            <inherited>true</inherited>
            <artifactId>maven-javadoc-plugin</artifactId>
            <executions>
              <execution>
                <id>attach-javadocs</id>
                <goals>
                  <goal>jar</goal>
                </goals>
              </execution>
            </executions>
          </plugin>
          <plugin>
            <inherited>true</inherited>
            <artifactId>maven-deploy-plugin</artifactId>
            <configuration>
              <updateReleaseInfo>true</updateReleaseInfo>
            </configuration>
          </plugin>
        </plugins>
      </build>
    </profile>
  </profiles>

</project>
<!-- END SNIPPET: superpom -->

Super POM 的作用

1. 定义了一个ID为central的远程仓库（url即为这个仓库的地址），如果没有其它特殊的声明，maven模块（项目）所需要的构件（jar包等）都会到这个远程中央仓库中去下载；
2. 定义了一个插件仓库，这个插件仓库和上面定义的远程仓库用的是同一个仓库，maven模块（项目）所需要的插件包都会到这个远程中央仓库中去下载；

3. 定义了一组标准的配置变量，在maven模块（项目）的POM中可以通过${project.build.XX}来使用它们，如 ${project.build.directory}；

   <directory>${project.basedir}/target</directory>
   <outputDirectory>${project.build.directory}/classes</outputDirectory>
   <finalName>${project.artifactId}-${project.version}</finalName>
   <testOutputDirectory>${project.build.directory}/test-classes</testOutputDirectory>
   <sourceDirectory>${project.basedir}/src/main/java</sourceDirectory>
   <scriptSourceDirectory>${project.basedir}/src/main/scripts</scriptSourceDirectory>
   <testSourceDirectory>${project.basedir}/src/test/java</testSourceDirectory>