Maven的集合、继承（NEW）

Maven的聚合、继承（NEW）
<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.gc.user</groupId> <artifactId>user-aggregation</artifactId> <version>0.0.1-SNAPSHOT</version> <!-- 此处，类型为pom --> <packaging>pom</packaging> <!-- 将其它模块放到一起，集中执行命令 --> <modules> <module>../user-core</module> <module>../user-dao</module> </modules> </project>

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模块的继承

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引入继承带来的好处：

将各个模块中相同的配置定义到一个文件中，由其它模块来继承

提高pom文件配置的重用性，而且可以单点维护---单一职责原则！

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用法：

新建一个Maven项目，将其artifactId设置为user-parent

修改package属性为pom

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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>com.gc.user</groupId><artifactId>user-parent</artifactId><version>0.0.1-SNAPSHOT</version><packaging>pom</packaging><name>user-parent</name><url>http://maven.apache.org</url><!-- 常量的定义，子模块中通过${}就能使用此处定义的常量:单点维护 --><properties><project.version>0.0.1-SNAPSHOT</project.version><project.build.sourceEncoding>UTF-8</project.build.sourceEncoding><my.jar.source>d:/</my.jar.source><junit.version>4.10</junit.version></properties><!-- 如果不通过 dependencyManagement管理依赖，虽然子模块能够继承这些依赖， 但是会继承所有parent中的依赖！应该根据各个子模块的需求，灵活继承依赖， 所以使用dependencyManagement来管理，这样子模块声明了那些依赖，就继承哪些依赖 子类没有声明的依赖，就不会继承下去。 --><dependencyManagement><dependencies><!-- 子模块的依赖 --><dependency><groupId>com.gc.user</groupId><artifactId>user-core</artifactId><version>${project.version}</version></dependency><!-- 子模块的依赖 --><dependency><groupId>com.gc.user</groupId><artifactId>user-dao</artifactId><version>${project.version}</version></dependency><!-- 其它依赖 --><dependency><groupId>junit</groupId><artifactId>junit</artifactId><version>${junit.version}</version><scope>test</scope></dependency><dependency><groupId>org.hibernate</groupId><artifactId>hibernate-core</artifactId><version>4.2.6.Final</version></dependency><dependency><groupId>mysql</groupId><artifactId>mysql-connector-java</artifactId><version>5.1.26</version></dependency><dependency><groupId>log4j</groupId><artifactId>log4j</artifactId><version>1.2.16</version></dependency><dependency><groupId>org.mortbay.jetty</groupId><artifactId>servlet-api</artifactId><version>2.5-6.0.0</version><scope>provided</scope></dependency></dependencies></dependencyManagement></project>

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子模块user-core模块继承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><parent><groupId>com.gc.user</groupId><artifactId>user-parent</artifactId><version>0.0.1-SNAPSHOT</version></parent><artifactId>user-core</artifactId><!-- groupId和version将从parent继承，无需定义 --><packaging>jar</packaging>    <!-- properties将从parent继承，无需定义  -->    <name>user-core</name><dependencies><dependency><groupId>junit</groupId><artifactId>junit</artifactId><version>${junit.version}</version><scope>test</scope></dependency><dependency><groupId>org.hibernate</groupId><artifactId>hibernate-core</artifactId>                        <!-- version无需定义，会从parent继承下来 --></dependency><dependency><groupId>mysql</groupId><artifactId>mysql-connector-java</artifactId></dependency><dependency><groupId>log4j</groupId><artifactId>log4j</artifactId></dependency><dependency><groupId>org.mortbay.jetty</groupId><artifactId>servlet-api</artifactId><scope>provided</scope></dependency></dependencies></project>

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子模块user-dao模块继承parent模块

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<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.gc.user</groupId>  <artifactId>user-parent</artifactId>  <version>0.0.1-SNAPSHOT</version>  </parent>  <artifactId>user-dao</artifactId>  <packaging>jar</packaging>  <name>user-dao</name>  <dependencies>    <dependency>      <groupId>junit</groupId>      <artifactId>junit</artifactId>      <scope>test</scope>    </dependency>        <!-- 引入user-core，将会发生传递性依赖：user-core中的依赖是否会导入到本模块中，还要根据scope决定！ -->  <dependency>  <groupId>com.gc.user</groupId>  <artifactId>user-core</artifactId>  <exclusions>  <!-- 排除user-core模块中关于log4j的依赖 -->  <exclusion>  <groupId>log4j</groupId>  <artifactId>log4j</artifactId>  </exclusion>  </exclusions>  </dependency>    </dependencies></project>

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将聚合与继承集中到parent模块的POM中?

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user-parent模块，既提供聚合又提供继承

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<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.gc.user</groupId><artifactId>user-parent</artifactId><version>0.0.1-SNAPSHOT</version><packaging>pom</packaging><!-- 将其它模块放到一起，集中执行命令 --><modules><module>../user-core</module><module>../user-dao</module></modules><name>user-parent</name><url>http://maven.apache.org</url><!-- 常量的定义，子模块中通过${}就能使用此处定义的常量:单点维护 --><properties><project.version>0.0.1-SNAPSHOT</project.version><project.build.sourceEncoding>UTF-8</project.build.sourceEncoding><my.jar.source>d:/</my.jar.source><junit.version>4.10</junit.version></properties><!-- 如果不通过 dependencyManagement管理依赖，虽然子模块能够继承这些依赖， 但是会继承所有parent中的依赖！应该根据各个子模块的需求，灵活继承依赖， 所以使用dependencyManagement来管理，这样子模块声明了那些依赖，就继承哪些依赖 子类没有声明的依赖，就不会继承下去。 --><dependencyManagement><dependencies><!-- 子模块的依赖 --><dependency><groupId>com.gc.user</groupId><artifactId>user-core</artifactId><version>${project.version}</version></dependency><!-- 子模块的依赖 --><dependency><groupId>com.gc.user</groupId><artifactId>user-dao</artifactId><version>${project.version}</version></dependency><!-- 其它依赖 --><dependency><groupId>junit</groupId><artifactId>junit</artifactId><version>${junit.version}</version><scope>test</scope></dependency><dependency><groupId>org.hibernate</groupId><artifactId>hibernate-core</artifactId><version>4.2.6.Final</version></dependency><dependency><groupId>mysql</groupId><artifactId>mysql-connector-java</artifactId><version>5.1.26</version></dependency><dependency><groupId>log4j</groupId><artifactId>log4j</artifactId><version>1.2.16</version></dependency><dependency><groupId>org.mortbay.jetty</groupId><artifactId>servlet-api</artifactId><version>2.5-6.0.0</version><scope>provided</scope></dependency></dependencies></dependencyManagement></project>

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