《Maven 实战》读书笔记（七） 聚合
1. 继承
之前我们学习Maven的聚合机制遗留个问题，就是多个模块的pom.xml文件的内容出现了冗余、重复的内容，解决这个问题其实使用Maven的继承机制即可，就像Java的继承一样，父类就像一个模板，子类继承自父类，那么有些通用的方法、变量都不必在子类中再重复声明了，具体Java继承在内存中的表现形式可以参考
http://suhuanzheng7784877.iteye.com/blog/1000635
和http://suhuanzheng7784877.iteye.com/blog/1000700 中的部分内容。Maven的继承机制类似，在一个父级别的Maven的pom文件中定义了相关的常量、依赖、插件等等配置后，实际项目模块可以继承此父项目的pom文件，重复的项不必显示的再声明一遍了，相当于父Maven项目就是个模板，等着其他子模块去继承。不过父Maven项目要高度抽象，高度提取公共的部分（交集）。笔者使用了先前的聚合项目模块做的父模板pom，实际上很多机构也是这么实施的。
<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/maven-v4_0_0.xsd"> <modelVersion>4.0.0</modelVersion> <groupId>com.liuyan.account</groupId> <artifactId>MavenAccount-aggregator</artifactId> <version>0.0.1-SNAPSHOT</version> <packaging>pom</packaging> <properties> <springversion>2.5.6</springversion> <junitversion>2.5.6</junitversion> </properties> <dependencies> <dependency> <groupId>org.springframework</groupId> <artifactId>spring-core</artifactId> <version>${springversion}</version> </dependency> <dependency> <groupId>org.springframework</groupId> <artifactId>spring-beans</artifactId> <version>${springversion}</version> </dependency> <dependency> <groupId>org.springframework</groupId> <artifactId>spring-context</artifactId> <version>${springversion}</version> </dependency> <dependency> <groupId>org.springframework</groupId> <artifactId>spring-context-support</artifactId> <version>${springversion}</version> </dependency> <dependency> <groupId>javax.mail</groupId> <artifactId>mail</artifactId> <version>1.4.1</version> </dependency> <dependency> <groupId>junit</groupId> <artifactId>junit</artifactId> <version>4.7</version> <scope>test</scope> </dependency> <dependency> <groupId>com.icegreen</groupId> <artifactId>greenmail</artifactId> <version>1.3.1b</version> <scope>test</scope> </dependency> </dependencies> <build> <resources> <resource> <directory>src/main/resource</directory> </resource> </resources> <plugins> <plugin> <groupId>org.apache.maven.plugins</groupId> <artifactId>maven-source-plugin</artifactId> <version>2.1.1</version> <executions> <execution> <id>buildSource</id> <goals> <goal>jar-no-fork</goal> </goals> <inherited>false</inherited> <configuration> </configuration> </execution> </executions> </plugin> <plugin> <groupId>org.apache.maven.plugins</groupId> <artifactId>maven-compiler-plugin</artifactId> <configuration> <target>1.5</target> </configuration> </plugin> </plugins> </build> <modules> <module>../MavenAccount-email</module> <module>../MavenAccount-persist</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/maven-v4_0_0.xsd"> <modelVersion>4.0.0</modelVersion> <artifactId>MavenAccount-email</artifactId> <packaging>jar</packaging> <parent> <groupId>com.liuyan.account</groupId> <artifactId>MavenAccount-aggregator</artifactId> <version>0.0.1-SNAPSHOT</version> <relativePath>../MavenAccount-aggregator/pom.xml</relativePath> </parent> </project>