（四）maven的聚合和继承
1.聚合
在一个POM文件中完成所有模块的编译，打包工作，而不用每个模块单独执行命令。
好处：简化过程,一个地方编译所有的模块
注意：
packaging为pom
被聚合的模块的路径需使用../在当前POM.xml目录上跳跃到上一级目录，否则定位不到模块
<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>com.hqh.maven.user</groupId> <artifactId>user-aggregation</artifactId> <version>0.0.1-SNAPSHOT</version> <!--聚合的packaging属性为pom--> <packaging>pom</packaging> <modules> <!--路径要正确--> <module>../user-log</module> <module>../user-core</module> <module>../user-dao</module> <module>../user-service</module> </modules></project>
<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"><!-- 模型版本 --><modelVersion>4.0.0</modelVersion><!-- 聚合：聚合其它模块 --><modules><module>../user-log</module><module>../user-core</module><module>../user-dao</module><module>../user-service</module></modules><!-- 继承：超级pom的坐标，该pom中的配置用于其它模块继承所用 --><groupId>com.hqh.maven.user</groupId><artifactId>user-parent</artifactId><version>0.0.1-SNAPSHOT</version><packaging>pom</packaging><!-- 中心仓库 <repositories> <repository> <id>central</id> <name>my central repository</name> <url>http://xxx.xxx.org</url> <layout>default</layout> <snapshots> <enabled>false</enabled> </snapshots> <releases> <updatePolicy>false</updatePolicy> </releases> </repository> </repositories> --><!-- 单点维护属性，其它地方通过${name}来引用 --><properties><project.build.sourceEncoding>UTF-8</project.build.sourceEncoding><junit.version>4.10</junit.version></properties><!-- --><dependencyManagement><dependencies><!-- junit测试单元 --><dependency><groupId>junit</groupId><artifactId>junit</artifactId><version>${junit.version}</version><scope>test</scope></dependency><!-- 日志 --><dependency><groupId>log4j</groupId><artifactId>log4j</artifactId><version>1.2.16</version></dependency><dependency><groupId>org.slf4j</groupId><artifactId>slf4j-log4j12</artifactId><version>1.6.1</version></dependency><!-- ORM --><dependency><groupId>org.hibernate</groupId><artifactId>hibernate-core</artifactId><version>3.6.10.Final</version></dependency><dependency><groupId>javassist</groupId><artifactId>javassist</artifactId><version>3.8.0.GA</version></dependency><dependency><groupId>mysql</groupId><artifactId>mysql-connector-java</artifactId><version>5.1.25</version></dependency><!-- 模块 --><dependency><groupId>${project.groupId}</groupId><artifactId>user-log</artifactId><version>${project.version}</version></dependency><dependency><groupId>${project.groupId}</groupId><artifactId>user-core</artifactId><version>${project.version}</version></dependency><dependency><groupId>${project.groupId}</groupId><artifactId>user-service</artifactId><version>${project.version}</version></dependency><dependency><groupId>${project.groupId}</groupId><artifactId>user-dao</artifactId><version>${project.version}</version></dependency></dependencies></dependencyManagement></project>