《Maven官方文档》POM文件（一）

什么是POM？

POM(project object model)包含了工程信息和工程的配置细节，Maven使用POM文件来构建工程。POM文件包含了工程中的大部分默认值。举个例子，target是默认的构建目录，src/main/java是默认的源码目录，src/test/java是默认的测试源码目录，等等。

Maven2中的pom.xml就是Maven1中的project.xml。相比于在maven.xml中包含可执行的goal，现在goals和plugins都可以在pom.xml中配置。当执行一个task或者goal时，Maven会在当前目录下寻找并读取pom.xml来获取配置信息，然后执行goal。

能在pom.xml中声明的配置包括工程依赖(project dependencies)，插件(plugins)，可执行的目标(goals)，构建配置(build profiles)等等。其他信息，比如工程版本，描述，开发者，邮件列表等等也可以在pox.xml中声明。

Super POM

Super POM是Maven的默认POM文件，除非你显示的声明继承关系，否则所有的POM文件都是在Super POM的基础上的扩展，也就是说，Super POM中的的配置会被你的工程中创建的pom.xml继承。Maven 2.0.x中的Super POM代码如下：

 project 

 modelVersion 4.0.0 /modelVersion 

 name Maven Default Project /name 

 repositories 

 repository 

 id central /id 

 name Maven Repository Switchboard /name 

 layout default /layout 

 url http://repo1.maven.org/maven2 /url 

 snapshots 

 enabled false /enabled 

 /snapshots 

 /repository 

 /repositories 

 pluginRepositories 

 pluginRepository 

 id central /id 

 name Maven Plugin Repository /name 

 url http://repo1.maven.org/maven2 /url 

 layout default /layout 

 snapshots 

 enabled false /enabled 

 /snapshots 

 releases 

 updatePolicy never /updatePolicy 

 /releases 

 /pluginRepository 

 /pluginRepositories 

 build 

 directory target /directory 

 outputDirectory target/classes /outputDirectory 

 finalName ${artifactId}-${version} /finalName 

 testOutputDirectory target/test-classes /testOutputDirectory 

 sourceDirectory src/main/java /sourceDirectory 

 scriptSourceDirectory src/main/scripts /scriptSourceDirectory 

 testSourceDirectory src/test/java /testSourceDirectory 

 resources 

 resource 

 directory src/main/resources /directory 

 /resource 

 /resources 

 testResources 

 testResource 

 directory src/test/resources /directory 

 /testResource 

 /testResources 

 /build 

 reporting 

 outputDirectory target/site /outputDirectory 

 /reporting 

 profiles 

 profile 

 id release-profile /id 

 activation 

 property 

 name performRelease /name 

 /property 

 /activation 

 build 

 plugins 

 plugin 

 inherited true /inherited 

 groupId org.apache.maven.plugins /groupId 

 artifactId maven-source-plugin /artifactId 

 executions 

 execution 

 id attach-sources /id 

 goals 

 goal jar /goal 

 /goals 

 /execution 

 /executions 

 /plugin 

 plugin 

 inherited true /inherited 

 groupId org.apache.maven.plugins /groupId 

 artifactId maven-javadoc-plugin /artifactId 

 executions 

 execution 

 id attach-javadocs /id 

 goals 

 goal jar /goal 

 /goals 

 /execution 

 /executions 

 /plugin 

 plugin 

 inherited true /inherited 

 groupId org.apache.maven.plugins /groupId 

 artifactId maven-deploy-plugin /artifactId 

 configuration 

 updateReleaseInfo true /updateReleaseInfo 

 /configuration 

 /plugin 

 /plugins 

 /build 

 /profile 

 /profiles 

 /project 

下面是Maven 2.1.x的Super POM:

 project 

 modelVersion 4.0.0 /modelVersion 

 name Maven Default Project /name 

 repositories 

 repository 

 id central /id 

 name Maven Repository Switchboard /name 

 layout default /layout 

 url http://repo1.maven.org/maven2 /url 

 snapshots 

 enabled false /enabled 

 /snapshots 

 /repository 

 /repositories 

 pluginRepositories 

 pluginRepository 

 id central /id 

 name Maven Plugin Repository /name 

 url http://repo1.maven.org/maven2 /url 

 layout default /layout 

 snapshots 

 enabled false /enabled 

 /snapshots 

 releases 

 updatePolicy never /updatePolicy 

 /releases 

 /pluginRepository 

 /pluginRepositories 

 build 

 directory ${project.basedir}/target /directory 

 outputDirectory ${project.build.directory}/classes /outputDirectory 

 finalName ${project.artifactId}-${project.version} /finalName 

 testOutputDirectory ${project.build.directory}/test-classes /testOutputDirectory 

 sourceDirectory ${project.basedir}/src/main/java /sourceDirectory 

 !-- TODO: MNG-3731 maven-plugin-tools-api 2.4.4 expect this to be relative... -- 

 scriptSourceDirectory src/main/scripts /scriptSourceDirectory 

 testSourceDirectory ${project.basedir}/src/test/java /testSourceDirectory 

 resources 

 resource 

 directory ${project.basedir}/src/main/resources /directory 

 /resource 

 /resources 

 testResources 

 testResource 

 directory ${project.basedir}/src/test/resources /directory 

 /testResource 

 /testResources 

 pluginManagement 

 plugins 

 plugin 

 artifactId maven-antrun-plugin /artifactId 

 version 1.3 /version 

 /plugin 

 plugin 

 artifactId maven-assembly-plugin /artifactId 

 version 2.2-beta-2 /version 

 /plugin 

 plugin 

 artifactId maven-clean-plugin /artifactId 

 version 2.2 /version 

 /plugin 

 plugin 

 artifactId maven-compiler-plugin /artifactId 

 version 2.0.2 /version 

 /plugin 

 plugin 

 artifactId maven-dependency-plugin /artifactId 

 version 2.0 /version 

 /plugin 

 plugin 

 artifactId maven-deploy-plugin /artifactId 

 version 2.4 /version 

 /plugin 

 plugin 

 artifactId maven-ear-plugin /artifactId 

 version 2.3.1 /version 

 /plugin 

 plugin 

 artifactId maven-ejb-plugin /artifactId 

 version 2.1 /version 

 /plugin 

 plugin 

 artifactId maven-install-plugin /artifactId 

 version 2.2 /version 

 /plugin 

 plugin 

 artifactId maven-jar-plugin /artifactId 

 version 2.2 /version 

 /plugin 

 plugin 

 artifactId maven-javadoc-plugin /artifactId 

 version 2.5 /version 

 /plugin 

 plugin 

 artifactId maven-plugin-plugin /artifactId 

 version 2.4.3 /version 

 /plugin 

 plugin 

 artifactId maven-rar-plugin /artifactId 

 version 2.2 /version 

 /plugin 

 plugin 

 artifactId maven-release-plugin /artifactId 

 version 2.0-beta-8 /version 

 /plugin 

 plugin 

 artifactId maven-resources-plugin /artifactId 

 version 2.3 /version 

 /plugin 

 plugin 

 artifactId maven-site-plugin /artifactId 

 version 2.0-beta-7 /version 

 /plugin 

 plugin 

 artifactId maven-source-plugin /artifactId 

 version 2.0.4 /version 

 /plugin 

 plugin 

 artifactId maven-surefire-plugin /artifactId 

 version 2.4.3 /version 

 /plugin 

 plugin 

 artifactId maven-war-plugin /artifactId 

 version 2.1-alpha-2 /version 

 /plugin 

 /plugins 

 /pluginManagement 

 /build 

 reporting 

 outputDirectory ${project.build.directory}/site /outputDirectory 

 /reporting 

 profiles 

 profile 

 id release-profile /id 

 activation 

 property 

 name performRelease /name 

 value true /value 

 /property 

 /activation 

 build 

 plugins 

 plugin 

 inherited true /inherited 

 groupId org.apache.maven.plugins /groupId 

 artifactId maven-source-plugin /artifactId 

 executions 

 execution 

 id attach-sources /id 

 goals 

 goal jar /goal 

 /goals 

 /execution 

 /executions 

 /plugin 

 plugin 

 inherited true /inherited 

 groupId org.apache.maven.plugins /groupId 

 artifactId maven-javadoc-plugin /artifactId 

 executions 

 execution 

 id attach-javadocs /id 

 goals 

 goal jar /goal 

 /goals 

 /execution 

 /executions 

 /plugin 

 plugin 

 inherited true /inherited 

 groupId org.apache.maven.plugins /groupId 

 artifactId maven-deploy-plugin /artifactId 

 configuration 

 updateReleaseInfo true /updateReleaseInfo 

 /configuration 

 /plugin 

 /plugins 

 /build 

 /profile 

 /profiles 

 /project 

最小化POM

一个最小化的POM文件的要求如下：

project 标签作为顶层标签 modelVersion – 应该设为4.0.0 groupId – 工程开发组的唯一id artifactId – 工件(artifact)或工程(projrct)的唯一id version – 版本号

这里是一个最小化POM的例子：

 project 

 modelVersion 4.0.0 /modelVersion 

 groupId com.mycompany.app /groupId 

 artifactId my-app /artifactId 

 version 1 /version 

 /project 

在POM文件中需要声明 groupId ,  artifactId 和 version 。这三个值以 groupId : artifactId : version 的形式声明，它们组成了工程的完整名称。比如上面的例子，完整名称为”com.mycompany.app:my-app1″。

如第一节所说，如果配置细节没有显示的设置，Maven将会使用继承自Super POM默认配置。其中一个默认值就是包的类型(packaging type)，每个Maven工程都有一个包类型，如果没有在POM中设置，则默认为”jar”。

前面的Minimal POM中，其中 repositories 这个值没有设置，如果你使用minimal POM来构建你的工程，它将使用继承Super POM中的 repositories 值(http://repo.maven.apache.org/maven2)，当Maven在POM中找到依赖，它就会去这个地址下载依赖包。

转载自 并发编程网 - ifeve.com

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 https://maven.apache.org/xsd/maven-4.0.0.xsd modelVersion 4.0.0 /model
Maven pom 中配置依赖机制 依赖管理是 Maven 的一个核心特性。管理单个项目的依赖关系非常简单。管理由数百个模块组成的多模块项目和应用程序的依赖关系是可能的。Maven 使用定义良好的类路径和库版本在定义、创建和维护可重复的构建方面帮助很大。