Maven pom 配置

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>4.0.0</modelVersion> 
  <!– The Basics –> 
  <groupId>…</groupId> 
  <artifactId>…</artifactId> 
  <version>…</version> 
  <packaging>…</packaging> 
  <dependencies>…</dependencies> 
  <parent>…</parent> 
  <dependencyManagement>…</dependencyManagement> 
  <modules>…</modules> 
  <properties>…</properties> 
  <!– Build Settings –> 
  <build>…</build> 
  <reporting>…</reporting> 
  <!– More Project Information –> 
  <name>…</name> 
  <description>…</description> 
  <url>…</url> 
  <inceptionYear>…</inceptionYear> 
  <licenses>…</licenses> 
  <organization>…</organization> 
  <developers>…</developers> 
  <contributors>…</contributors> 
  <!– Environment Settings –> 
  <issueManagement>…</issueManagement> 
  <ciManagement>…</ciManagement> 
  <mailingLists>…</mailingLists> 
  <scm>…</scm> 
  <prerequisites>…</prerequisites> 
  <repositories>…</repositories> 
  <pluginRepositories>…</pluginRepositories> 
  <distributionManagement>…</distributionManagement> 
  <profiles>…</profiles> 
</project>

基本设置

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>4.0.0</modelVersion> 
  <groupId>org.codehaus.mojo</groupId> 
  <artifactId>my-project</artifactId> 
  <version>1.0</version> 
  <packaging>war</packaging> 
</project>

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

POM之间的关系

主要用于POM文件的复用。

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

  <dependencies> 
    <dependency> 
      <groupId>junit</groupId> 
      <artifactId>junit</artifactId> 
      <version>4.0</version> 
      <scope>test</scope> 
    </dependency> 
    … 
  </dependencies>

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

继承关系：继承其他pom.xml配置的机制。

比如父pom.xml：

<project> 
  [...] 
  <dependencies> 
    <dependency> 
      <groupId>junit</groupId> 
      <artifactId>junit</artifactId> 
      <version>4.4</version> 
      <scope>test</scope> 
    </dependency> 
  </dependencies> 
  [...] 
</project>

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.proficio</groupId> 
  <artifactId>proficio</artifactId> 
  <version>1.0-SNAPSHOT</version> 
</parent> 
[...]

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>4.0.0</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>${project.artifactId}-${project.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> 
    <pluginManagement> 
       <plugins> 
         <plugin> 
           <artifactId>maven-antrun-plugin</artifactId> 
           <version>1.1</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>2.3</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>2.4</version> 
         </plugin> 
         <plugin> 
           <artifactId>maven-plugin-plugin</artifactId> 
           <version>2.4.1</version> 
         </plugin> 
         <plugin> 
           <artifactId>maven-rar-plugin</artifactId> 
           <version>2.2</version> 
         </plugin> 
         <plugin>                
           <artifactId>maven-release-plugin</artifactId> 
           <version>2.0-beta-7</version> 
         </plugin> 
         <plugin>                
           <artifactId>maven-resources-plugin</artifactId> 
           <version>2.2</version> 
         </plugin> 
         <plugin> 
           <artifactId>maven-site-plugin</artifactId> 
           <version>2.0-beta-6</version> 
         </plugin> 
         <plugin> 
           <artifactId>maven-source-plugin</artifactId> 
           <version>2.0.4</version> 
         </plugin>          
         <plugin> 
            <artifactId>maven-surefire-plugin</artifactId> 
            <version>2.4.2</version> 
         </plugin> 
         <plugin> 
           <artifactId>maven-war-plugin</artifactId> 
           <version>2.1-alpha-1</version> 
         </plugin> 
       </plugins> 
     </pluginManagement> 
  </build> 
  <reporting> 
    <outputDirectory>target/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>

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

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>4.0.0</modelVersion> 
  <groupId>org.codehaus.mojo</groupId> 
  <artifactId>my-parent</artifactId> 
  <version>2.0</version> 
  <modules> 
    <module>my-project<module> 
  </modules> 
</project>

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${env.PATH}
2. project.x：pom文件中的属性，比如：<project><version>1.0</version></project>，引用方式：${project.version}
3. settings.x：settings.xml文件中的属性，比如：<settings><offline>false</offline></settings>，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：<properties><installDir>c:/apps/cargo-installs</installDir></properties>，引用方式：${installDir}

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"> 
  … 
  <!– "Project Build" contains more elements than just the BaseBuild set –> 
  <build>…</build> 
  <profiles> 
    <profile> 
      <!– "Profile Build" contains a subset of "Project Build"s elements –> 
      <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/plexus</targetPath> 
        <filtering>false</filtering> 
        <directory>${basedir}/src/main/plexus</directory> 
        <includes> 
          <include>configuration.xml</include> 
        </includes> 
        <excludes> 
          <exclude>**/*.properties</exclude> 
        </excludes> 
      </resource> 
    </resources>

Plugins：设置构建的插件

  <build> 
    … 
    <plugins> 
      <plugin> 
        <groupId>org.apache.maven.plugins</groupId> 
        <artifactId>maven-jar-plugin</artifactId> 
        <version>2.0</version> 
        <extensions>false</extensions> 
        <inherited>true</inherited> 
        <configuration> 
          <classifier>test</classifier> 
        </configuration> 
        <dependencies>…</dependencies> 
        <executions>…</executions> 
      </plugin>