maven-Maven的聚合模块和pom的继承使用

xiaoxiao2021-12-14 24

原文地址:http://yanan0628.iteye.com/blog/2270411

1.什么是maven的聚合模块？

聚合模块为项目目录的最顶层，其他模块作为聚合模块子目录而存在。目的是为一次构建多个项目模块。

1.1 项目结构

我自己化了一个关于项目的关系：

1.2 pom标签配置-module

maven-aggregate作为maven pom项目，需要定义pom.xml的 packaging 为 pom类型

我们还是参照 maven的依赖特性,冲突解决(五) 创建 maven-01 maven-02 maven-03工程，通过maven-aggregate pom工程对这三个maven项目做一个聚合，配置如下：

对 maven-aggregate执行下mvn clean compile

Xml代码 [INFO] Scanning for projects... [WARNING] [WARNING] Some problems were encountered while building the effective model for com.sohu.train:maven-02:jar:1.0-SNAPSHORT [WARNING] 'dependencies.dependency.exclusions.exclusion.groupId' for junit:junit:jar is missing. @ line 38, column 16 [WARNING] 'dependencies.dependency.exclusions.exclusion.artifactId' for junit:junit:jar is missing. @ line 38, column 16 [WARNING] [WARNING] It is highly recommended to fix these problems because they threaten the stability of your build. [WARNING] [WARNING] For this reason, future Maven versions might no longer support building such malformed projects. [WARNING] [INFO] ------------------------------------------------------------------------ [INFO] Reactor Build Order: //构建 maven 的反应堆，执行清理编译的顺序 [INFO] [INFO] maven-02 [INFO] maven-01 [INFO] maven-03 [INFO] maven-aggregate [INFO] [INFO] ------------------------------------------------------------------------ [INFO] Building maven-02 1.0-SNAPSHORT [INFO] ------------------------------------------------------------------------ [INFO] [INFO] --- maven-clean-plugin:2.5:clean (default-clean) @ maven-02 --- [INFO] Deleting E:\train\test\maven-02\target [INFO] [INFO] --- maven-resources-plugin:2.6:resources (default-resources) @ maven-02 --- [INFO] Using 'UTF-8' encoding to copy filtered resources. [INFO] skip non existing resourceDirectory E:\train\test\maven-02\src\main\resources [INFO] [INFO] --- maven-compiler-plugin:3.1:compile (default-compile) @ maven-02 --- [INFO] Changes detected - recompiling the module! [INFO] Compiling 1 source file to E:\train\test\maven-02\target\classes [INFO] [INFO] ------------------------------------------------------------------------ [INFO] Building maven-01 1.0-SNAPSHOT [INFO] ------------------------------------------------------------------------ [INFO] [INFO] --- maven-clean-plugin:2.5:clean (default-clean) @ maven-01 --- [INFO] Deleting E:\train\test\maven-01\target [INFO] [INFO] --- maven-resources-plugin:2.6:resources (default-resources) @ maven-01 --- [INFO] Using 'UTF-8' encoding to copy filtered resources. [INFO] Copying 1 resource [INFO] [INFO] --- maven-compiler-plugin:3.1:compile (default-compile) @ maven-01 --- [INFO] Changes detected - recompiling the module! [INFO] Compiling 1 source file to E:\train\test\maven-01\target\classes [INFO] [INFO] ------------------------------------------------------------------------ [INFO] Building maven-03 0.0.1-SNAPSHOT [INFO] ------------------------------------------------------------------------ [INFO] [INFO] --- maven-clean-plugin:2.5:clean (default-clean) @ maven-03 --- [INFO] Deleting E:\train\test\maven-03\target [INFO] [INFO] --- maven-resources-plugin:2.6:resources (default-resources) @ maven-03 --- [INFO] Using 'UTF-8' encoding to copy filtered resources. [INFO] skip non existing resourceDirectory E:\train\test\maven-03\src\main\resources [INFO] [INFO] --- maven-compiler-plugin:3.1:compile (default-compile) @ maven-03 --- [INFO] Changes detected - recompiling the module! [INFO] Compiling 1 source file to E:\train\test\maven-03\target\classes [INFO] [INFO] ------------------------------------------------------------------------ [INFO] Building maven-aggregate 0.0.1-SNAPSHOT [INFO] ------------------------------------------------------------------------ [INFO] [INFO] --- maven-clean-plugin:2.5:clean (default-clean) @ maven-aggregate --- [INFO] ------------------------------------------------------------------------ [INFO] Reactor Summary: // 可以看到对3个maven项目一起执行编译 [INFO] [INFO] maven-02 ........................................... SUCCESS [ 1.874 s] [INFO] maven-01 ........................................... SUCCESS [ 0.108 s] [INFO] maven-03 ........................................... SUCCESS [ 0.158 s] [INFO] maven-aggregate .................................... SUCCESS [ 0.002 s] [INFO] ------------------------------------------------------------------------ [INFO] BUILD SUCCESS [INFO] ------------------------------------------------------------------------ [INFO] Total time: 2.263 s [INFO] Finished at: 2016-01-15T14:35:41+08:00 [INFO] Final Memory: 14M/227M [INFO] ------------------------------------------------------------------------ 这样我们就完成 maven对子模块的聚合，像我们平常用的dubbo jetty tomcat spring hibernate等等都是按模块去开发，一次编译各个模块都能紧密联系在一起了。我们在平常开发项目也需要适当的去分模块开发，这是dubbo的子模块，分了很多子模块：

2.什么是pom继承？

pom继承是为了抽出重复配置，通常配置在父模块中，为子模块提供使用，这样可以做到“一处声明，处处使用”。

2.1 继承结构

2.2 pom标签配置-parent,*Management

1.常用的pom被继承的元素

Xml代码 groupId ：项目组 ID ，项目坐标的核心元素； version ：项目版本，项目坐标的核心元素； description ：项目的描述信息； properties ：自定义的 Maven 属性； dependencies ：项目的依赖配置； dependencyManagement ：醒目的依赖管理配置； repositories ：项目的仓库配置； build ：包括项目的源码目录配置、输出目录配置、插件配置、插件管理配置等；

1.配置maven-aggregate pom文件：

Xml代码 <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.sohu.train</groupId> <artifactId>maven-aggregate</artifactId> <version>0.0.1-SNAPSHOT</version> <packaging>pom</packaging>  <modules> <module>../maven-01</module> <module>../maven-02</module> <module>../maven-03</module> </modules>  <properties> <junit.version>3.8.1</junit.version> </properties>  <dependencyManagement> <dependencies> <dependency> <groupId>junit</groupId> <artifactId>junit</artifactId> <version>${junit.version}</version> <scope>test</scope> </dependency> </dependencies> </dependencyManagement> </project>

maven-01,maven-02,maven-03 需要配置parent ,dependencies，同时对junit做一个依赖,3个工程的pom配置如下：

Xml代码 <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.sohu.train</groupId> <artifactId>maven-aggregate</artifactId> <version>0.0.1-SNAPSHOT</version> <relativePath>../maven-aggregate/pom.xml</relativePath> </parent> <artifactId>maven-03</artifactId> <packaging>jar</packaging>  <dependencies> <dependency> <groupId>junit</groupId> <artifactId>junit</artifactId> </dependency> </dependencies> </project>

这样就完成pom的继承，讲公用的jar一次配置，就可以实现多处引用了。

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