Maven 中的继承与聚合

先贴一个parent 模块的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.mycompany.myproject</groupId>  <artifactId>myproject-parent</artifactId>  <version>0.0.1-SNAPSHOT</version>  <packaging>pom</packaging>  <name>myproject-parent</name>  <url>http://maven.apache.org</url>  <properties>    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>    <spring.version>3.2.6.RELEASE</spring.version>  </properties>    <modules>   <module>../example</module>  </modules>  <dependencyManagement>  <dependencies>    <dependency><groupId>org.springframework</groupId><artifactId>spring-beans</artifactId><version>${spring.version}</version>    </dependency>    <dependency><groupId>org.springframework</groupId><artifactId>spring-core</artifactId><version>${spring.version}</version></dependency><dependency><groupId>org.springframework</groupId><artifactId>spring-context</artifactId><version>${spring.version}</version></dependency><dependency><groupId>org.springframework</groupId><artifactId>spring-web</artifactId><version>${spring.version}</version></dependency><dependency><groupId>org.springframework</groupId><artifactId>spring-aop</artifactId><version>${spring.version}</version></dependency><dependency><groupId>org.springframework</groupId><artifactId>spring-webmvc</artifactId><version>${spring.version}</version></dependency>  </dependencies>  </dependencyManagement>  <dependencies>    <dependency>      <groupId>junit</groupId>      <artifactId>junit</artifactId>      <version>4.11</version>      <scope>test</scope>    </dependency>   <dependency> <!--for org.hamcrest.Matchers--><groupId>org.hamcrest</groupId><artifactId>hamcrest-library</artifactId><version>1.3</version><scope>test</scope></dependency><dependency><groupId>log4j</groupId><artifactId>log4j</artifactId><version>1.2.17</version></dependency>  </dependencies></project>

子模块的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>  <parent>    <groupId>com.mycompany.myproject</groupId>    <artifactId>myproject-parent</artifactId>    <version>0.0.1-SNAPSHOT</version>    <relativePath>../myproject-parent/pom.xml</relativePath>  </parent>    <artifactId>peter-user</artifactId>  <packaging>war</packaging>  <dependencies>    <dependency><groupId>org.springframework</groupId><artifactId>spring-beans</artifactId>    </dependency>    <dependency><groupId>org.springframework</groupId><artifactId>spring-core</artifactId></dependency><dependency><groupId>org.springframework</groupId><artifactId>spring-context</artifactId></dependency><dependency><groupId>org.springframework</groupId><artifactId>spring-web</artifactId></dependency><dependency><groupId>org.springframework</groupId><artifactId>spring-aop</artifactId></dependency><dependency><groupId>org.springframework</groupId><artifactId>spring-webmvc</artifactId></dependency>  </dependencies></project>

继承：
1.子模块可以继承parent中所有关于GAV的属性，artifactId除外
2.子模块可以继承parent中properties
3.子模块可以继承parent中的dependencies，比如子模块都不用再添加log4j的依赖了，
但是这样也容易导致子模块中添加了不需要的模块。此时需要使用dependencyManagement，子模块pom.xml中只需要添加GA，这样也省去了很多麻烦。

聚合：
将所有开放的子模块使用modules打包，这样就不需要每个模块单独编译，打包了。