pom.xml详解



一、什么是POM

Project Object Model，项目对象模型。通过xml格式保存的pom.xml文件。作用类似ant的build.xml文件，功能更强大。该文件用于管理：源代码、配置文件、开发者的信息和角色、问题追踪系统、组织信息、项目授权、项目的url、项目的依赖关系等等。

一个完整的pom.xml文件，放置在项目的根目录下。

<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>4.0.0modelVersion>
  >
  <groupId>…groupId>
  <artifactId>…artifactId>
  <version>…version>
  <packaging>…packaging>
  <dependencies>…dependencies>
  <parent>…parent>
  <dependencyManagement>…dependencyManagement>
  <modules>…modules>
  <properties>…properties>
  >
  <build>…build>
  <reporting>…reporting>
  >
  <name>…name>
  <description>…description>
  <url>…url>
  <inceptionYear>…inceptionYear>
  <licenses>…licenses>
  <organization>…organization>
  <developers>…developers>
  <contributors>…contributors>
  >
  <issueManagement>…issueManagement>
  <ciManagement>…ciManagement>
  <mailingLists>…mailingLists>
  <scm>…scm>
  <prerequisites>…prerequisites>
  <repositories>…repositories>
  <pluginRepositories>…pluginRepositories>
  <distributionManagement>…distributionManagement>
  <profiles>…profiles>
project>

  4.0.0
  
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二、基本设置

1、maven的协作相关属性

<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>4.0.0modelVersion>
  <groupId>org.codehaus.mojogroupId>
  <artifactId>my-projectartifactId>
  <version>1.0version>
  <packaging>warpackaging>
project>

  4.0.0
  org.codehaus.mojo
  my-project
  1.0
  war

1. groupId : 组织标识，例如：org.codehaus.mojo，在M2_REPO目录下，将是: org/codehaus/mojo目录。
2. artifactId : 项目名称，例如：my-project，在M2_REPO目录下，将是：org/codehaus/mojo/my-project目录。
3. version : 版本号，例如：1.0，在M2_REPO目录下，将是：org/codehaus/mojo/my-project/1.0目录。
4. packaging : 打包的格式，可以为：pom , jar , maven-plugin , ejb , war , ear , rar , par

2、POM之间的关系

主要用于POM文件的复用。

a）依赖关系：依赖关系列表（dependency list）是POM的重要部分

<dependencies>
   <dependency>
     <groupId>junitgroupId>
     <artifactId>junitartifactId>
     <version>4.0version>
     <scope>testscope>
   dependency>
   …
 dependencies>

 
    
      junit
      junit
      4.0
      test
    
    …
  

1. groupId , artifactId , version :
2. scope : compile(default),provided,runtime,test,system
3. exclusions

b）继承关系：继承其他pom.xml配置的机制。

比如父pom.xml：

<project>
  [...]
  <dependencies>
    <dependency>
      <groupId>junitgroupId>
      <artifactId>junitartifactId>
      <version>4.4version>
      <scope>testscope>
    dependency>
  dependencies>
  [...]
project>

  [...]
  
    
      junit
      junit
      4.4
      test
    
  
  [...]

在子pom.xml文件继承它的依赖（还可以继承其他的：developers and contributors、plugin lists、reports lists、plugin executions with matching ids、plugin configuration）：

[...]
<parent>
<groupId>com.devzuz.mvnbook.proficiogroupId>
  <artifactId>proficioartifactId>
  <version>1.0-SNAPSHOTversion>
parent>
[...]

[...]

com.devzuz.mvnbook.proficio
  proficio
  1.0-SNAPSHOT

[...]

在这种机制下，maven还提供了一个类似java.lang.Object的顶级父pom.xml文件：

<project>
  <modelVersion>4.0.0modelVersion>
  <name>Maven Default Projectname>
  <repositories>
    <repository>
      <id>centralid>
      <name>Maven Repository Switchboardname>
      <layout>defaultlayout>
      <url>http://repo1.maven.org/maven2url>
      <snapshots>
        <enabled>falseenabled>
      snapshots>
    repository>
  repositories>
  <pluginRepositories>
    <pluginRepository>
      <id>centralid>
      <name>Maven Plugin Repositoryname>
      <url>http://repo1.maven.org/maven2url>
      <layout>defaultlayout>
      <snapshots>
        <enabled>falseenabled>
      snapshots>
      <releases>
        <updatePolicy>neverupdatePolicy>
      releases>
    pluginRepository>
  pluginRepositories>
  <build>
    <directory>targetdirectory>
    <outputDirectory>target/classesoutputDirectory>
    <finalName>${project.artifactId}-${project.version}finalName>
    <testOutputDirectory>target/test-classestestOutputDirectory>
    <sourceDirectory>src/main/javasourceDirectory>
    <scriptSourceDirectory>src/main/scriptsscriptSourceDirectory>
    <testSourceDirectory>src/test/javatestSourceDirectory>
    <resources>
      <resource>
        <directory>src/main/resourcesdirectory>
      resource>
    resources>
    <testResources>
      <testResource>
        <directory>src/test/resourcesdirectory>
      testResource>
    testResources>
    <pluginManagement>
       <plugins>
         <plugin>
           <artifactId>maven-antrun-pluginartifactId>
           <version>1.1version>
         plugin>
         <plugin>
           <artifactId>maven-assembly-pluginartifactId>
           <version>2.2-beta-2version>
         plugin>
         <plugin>
           <artifactId>maven-clean-pluginartifactId>
           <version>2.2version>
         plugin>
         <plugin>
           <artifactId>maven-compiler-pluginartifactId>
           <version>2.0.2version>
         plugin>
         <plugin>
           <artifactId>maven-dependency-pluginartifactId>
           <version>2.0version>
         plugin>
         <plugin>
           <artifactId>maven-deploy-pluginartifactId>
           <version>2.3version>
         plugin>
         <plugin>
           <artifactId>maven-ear-pluginartifactId>
           <version>2.3.1version>
         plugin>
         <plugin>
           <artifactId>maven-ejb-pluginartifactId>
           <version>2.1version>
         plugin>
         <plugin>
           <artifactId>maven-install-pluginartifactId>
           <version>2.2version>
         plugin>
         <plugin>
           <artifactId>maven-jar-pluginartifactId>
           <version>2.2version>
         plugin>
         <plugin>
           <artifactId>maven-javadoc-pluginartifactId>
           <version>2.4version>
         plugin>
         <plugin>
           <artifactId>maven-plugin-pluginartifactId>
           <version>2.4.1version>
         plugin>
         <plugin>
           <artifactId>maven-rar-pluginartifactId>
           <version>2.2version>
         plugin>
         <plugin>
           <artifactId>maven-release-pluginartifactId>
           <version>2.0-beta-7version>
         plugin>
         <plugin>
           <artifactId>maven-resources-pluginartifactId>
           <version>2.2version>
         plugin>
         <plugin>
           <artifactId>maven-site-pluginartifactId>
           <version>2.0-beta-6version>
         plugin>
         <plugin>
           <artifactId>maven-source-pluginartifactId>
           <version>2.0.4version>
         plugin>
         <plugin>
            <artifactId>maven-surefire-pluginartifactId>
            <version>2.4.2version>
         plugin>
         <plugin>
           <artifactId>maven-war-pluginartifactId>
           <version>2.1-alpha-1version>
         plugin>
       plugins>
     pluginManagement>
  build>
  <reporting>
    <outputDirectory>target/siteoutputDirectory>
  reporting>
  <profiles>
    <profile>
      <id>release-profileid>
      <activation>
        <property>
          <name>performReleasename>
          <value>truevalue>
        property>
      activation>
      <build>
        <plugins>
          <plugin>
            <inherited>trueinherited>
            <groupId>org.apache.maven.pluginsgroupId>
            <artifactId>maven-source-pluginartifactId>
            <executions>
              <execution>
                <id>attach-sourcesid>
                <goals>
                  <goal>jargoal>
                goals>
              execution>
            executions>
          plugin>
          <plugin>
            <inherited>trueinherited>
            <groupId>org.apache.maven.pluginsgroupId>
            <artifactId>maven-javadoc-pluginartifactId>
            <executions>
              <execution>
                <id>attach-javadocsid>
                <goals>
                  <goal>jargoal>
                goals>
              execution>
            executions>
          plugin>
          <plugin>
            <inherited>trueinherited>
            <groupId>org.apache.maven.pluginsgroupId>
            <artifactId>maven-deploy-pluginartifactId>
            <configuration>
              <updateReleaseInfo>trueupdateReleaseInfo>
            configuration>
          plugin>
        plugins>
      build>
    profile>
  profiles>
project>

  4.0.0
  Maven Default Project
  
    
      central
      Maven Repository Switchboard
      default
      http://repo1.maven.org/maven2
      
        false
      
    
  
  
    
      central
      Maven Plugin Repository
      http://repo1.maven.org/maven2
      default
      
        false
      
      
        never
      
    
  
  
    target
    target/classes
    ${project.artifactId}-${project.version}
    target/test-classes
    src/main/java
    src/main/scripts
    src/test/java
    
      
        src/main/resources
      
    
    
      
        src/test/resources
      
    
    
       
         
           maven-antrun-plugin
           1.1
               
         
           maven-assembly-plugin
           2.2-beta-2
         
         
           maven-clean-plugin
           2.2
         
         
           maven-compiler-plugin
           2.0.2
         
         
           maven-dependency-plugin
           2.0
         
         
           maven-deploy-plugin
           2.3
         
         
           maven-ear-plugin
           2.3.1
         
         
           maven-ejb-plugin
           2.1
         
         
           maven-install-plugin
           2.2
         
         
           maven-jar-plugin
           2.2
         
         
           maven-javadoc-plugin
           2.4
         
         
           maven-plugin-plugin
           2.4.1
         
         
           maven-rar-plugin
           2.2
         
                        
           maven-release-plugin
           2.0-beta-7
         
                        
           maven-resources-plugin
           2.2
         
         
           maven-site-plugin
           2.0-beta-6
         
         
           maven-source-plugin
           2.0.4
                  
         
            maven-surefire-plugin
            2.4.2
         
         
           maven-war-plugin
           2.1-alpha-1
         
       
     
  
  
    target/site
  
  
    
      release-profile
      
        
          performRelease
          true
        
      
      
        
          
            true
            org.apache.maven.plugins
            maven-source-plugin
            
              
                attach-sources
                
                  jar
                
              
            
          
          
            true
            org.apache.maven.plugins
            maven-javadoc-plugin
            
              
                attach-javadocs
                
                  jar
                
              
            
          
          
            true
            org.apache.maven.plugins
            maven-deploy-plugin
            
              true
            
          
        
      
    
  

可以通过下面命令查看当前pom.xml受到超pom.xml文件的影响：
mvn help:effective-pom

c）聚合关系：用于将多个maven项目聚合为一个大的项目。

<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>4.0.0modelVersion>
  <groupId>org.codehaus.mojogroupId>
  <artifactId>my-parentartifactId>
  <version>2.0version>
  <modules>
    <module>my-project<module>
  modules>
project>

  4.0.0
  org.codehaus.mojo
  my-parent
  2.0
  
    my-project
  

3、属性

maven的属性，是值的占位符，类似EL，类似ant的属性，比如${X}，可用于pom文件任何赋值的位置。有以下分类：

1. env.X：操作系统环境变量，比如${env.PATH}
2. project.x：pom文件中的属性，比如：1.0，引用方式：${project.version}
3. settings.x：settings.xml文件中的属性，比如：false，引用方式：${settings.offline}
4. Java System Properties：java.lang.System.getProperties()中的属性，比如java.home，引用方式：${java.home}
5. 自定义：在pom文件中可以：c:/apps/cargo-installs，引用方式：${installDir}

4、构建设置

构建有两种build标签：

<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">
  …
  >
  <build>…build>
  <profiles>
    <profile>
      >
      <build>…build>
    profile>
  profiles>
project>

  …
  
  …
  
    
      
      …
    
  

build中的主要标签：Resources和Plugins。

Resources：用于排除或包含某些资源文件

<resources>
  <resource>
    <targetPath>META-INF/plexustargetPath>
    <filtering>falsefiltering>
    <directory>${basedir}/src/main/plexusdirectory>
    <includes>
      <include>configuration.xmlinclude>
    includes>
    <excludes>
      <exclude>**/*.propertiesexclude>
    excludes>
  resource>
resources>

    
      
        META-INF/plexus
        false
        ${basedir}/src/main/plexus
        
          configuration.xml
        
        
          **/*.properties
        
      
    

Plugins：设置构建的插件

<build>
   …
   <plugins>
     <plugin>
       <groupId>org.apache.maven.pluginsgroupId>
       <artifactId>maven-jar-pluginartifactId>
       <version>2.0version>
       <extensions>falseextensions>
       <inherited>trueinherited>
       <configuration>
         <classifier>testclassifier>
       configuration>
       <dependencies>…dependencies>
       <executions>…executions>
     plugin>

 
    …
    
      
        org.apache.maven.plugins
        maven-jar-plugin
        2.0
        false
        true
        
          test
        
        …
        …