maven的聚合与继承

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maven

1.聚合与继承的关系

多模块maven项目中的聚合与继承是两个概念.

聚合主要是为了方便快速构建项目.

继承主要是为了消除重复配置.

聚合配置代码:

<modules>
  	<module>../Hello</module>  
  	<module>../HelloFriend</module>		
  	<module>../MakeFriends</module>
</modules>

其中module的路径为相对路径.

继承配置代码:

<parent>  
      	<groupId>com.zt.maven</groupId>
 	<artifactId>Project</artifactId>
  	<version>0.0.1-SNAPSHOT</version>
        <relativePath>../Project/pom.xml</relativePath>  
</parent>

在实际项目中,一般一个POM既是聚合POM,又是父POM.

Hello模块:

<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>
  <artifactId>Hello</artifactId>

  <name>Hello</name>
  <url>http://maven.apache.org</url>
 <parent>
 	<groupId>com.zt.maven</groupId>
 	<artifactId>Parent</artifactId>
 	<version>0.0.1-SNAPSHOT</version>
 	<relativePath>../Parent/pom.xml</relativePath>
 </parent>
  <properties>
    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
  </properties>

  <dependencies>
    <dependency>
      <groupId>junit</groupId>
      <artifactId>junit</artifactId>
      <scope>test</scope>
    </dependency>
  </dependencies>
</project>

HelloFirend模块:

<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>

  <artifactId>HelloFriend</artifactId>
  <packaging>jar</packaging>

  <name>HelloFriend</name>
  <url>http://maven.apache.org</url>

	<parent>
		<groupId>com.zt.maven</groupId>
		<artifactId>Parent</artifactId>
		<version>0.0.1-SNAPSHOT</version>
		<relativePath>../Parent/pom.xml</relativePath>
	</parent>

  <dependencies>
    <dependency>
      <groupId>junit</groupId>
      <artifactId>junit</artifactId>
    </dependency>
    
      <dependency>
      <groupId>cn.itcast.maven</groupId>
      <artifactId>Hello</artifactId>
    </dependency>
  </dependencies>
</project>

Parent模块:

<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>cn.itcast.maven</groupId>
  <artifactId>Parent</artifactId>
  <version>0.0.1-SNAPSHOT</version>
  <packaging>pom</packaging>

  <name>Parent</name>
  <url>http://maven.apache.org</url>
  <modules>
  		<module>../Hello</module>
  		<module>../HelloFriend</module>
  </modules>

  <properties>
    <project.build.sourceEncoding>GBK</project.build.sourceEncoding>
     <argLine>-Dfile.encoding=GBK</argLine>
  </properties>

	<dependencyManagement>
	  <dependencies>
	    <dependency>
	      <groupId>junit</groupId>
	      <artifactId>junit</artifactId>
	      <version>4.9</version>
	      <scope>test</scope>
	    </dependency>
	    
	    <dependency>
	    	<groupId>com.zt.maven</groupId>
	    	<artifactId>Hello</artifactId>
	    	<version>0.0.1-SNAPSHOT</version>
	    	<scope>compile</scope>
	    </dependency>
	    
	    <dependency>
	    	<groupId>com.zt.maven</groupId>
	    	<artifactId>HelloFriend</artifactId>
	    	<version>0.0.1-SNAPSHOT</version>
	    	<scope>compile</scope>
	    </dependency>
	       
	  </dependencies>
	 </dependencyManagement>
</project>

其中:Parent代码可以视为聚合模块也可以视为父模块.Hello和HelloFriend是被聚合模块的同时也是子模块.

maven中一般遵循约定,各种目录结构等.其实就是这种约定就是一种maven的超级POM.任何maven项目都继承了这个超级POM.对于maven2而言,超级POM在文件$MAVEN_HOME/lib/maven-model-builder-3.0.4.jar中的org/apache/maven/model/pom-4.0.0.xml:

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

<!-- START SNIPPET: superpom -->
<project>
  <modelVersion>4.0.0</modelVersion>
<!--首先定义了仓库及插件仓库.默认都为中央仓库-->
  <repositories>
    <repository>
      <id>central</id>
      <name>Central Repository</name>
      <url>http://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>http://repo.maven.apache.org/maven2</url>
      <layout>default</layout>
      <snapshots>
        <enabled>false</enabled>
      </snapshots>
      <releases>
        <updatePolicy>never</updatePolicy>
      </releases>
    </pluginRepository>
  </pluginRepositories>

<!--关于项目结构的定义-->
  <build>
    <directory>${project.basedir}/target</directory><!--主输出目录-->
    <outputDirectory>${project.build.directory}/classes</outputDirectory><!--主代码输出目录-->
    <finalName>${project.artifactId}-${project.version}</finalName><!--最终构件的名称格式-->
    <testOutputDirectory>${project.build.directory}/test-classes</testOutputDirectory><!--测试代码目录-->
    <sourceDirectory>${project.basedir}/src/main/java</sourceDirectory><!--主源码目录-->
    <scriptSourceDirectory>src/main/scripts</scriptSourceDirectory><!--脚本源码目录-->
    <testSourceDirectory>${project.basedir}/src/test/java</testSourceDirectory><!--测试源码目录-->
    <resources>
      <resource>
        <directory>${project.basedir}/src/main/resources</directory><!--主资源目录-->
      </resource>
    </resources>
    <testResources>
      <testResource>
        <directory>${project.basedir}/src/test/resources</directory><!--测试资源目录-->
      </testResource>
    </testResources>

<!--关于插件版本的定义-->
    <pluginManagement>
      <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>2.1</version>
        </plugin>
        <plugin>
          <artifactId>maven-release-plugin</artifactId>
          <version>2.0</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</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 -->