pom.xml
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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>4.0.0</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>
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>4.0.0</modelVersion> <groupId>org.codehaus.mojo</groupId> <artifactId>my-project</artifactId> <version>1.0</version> <packaging>war</packaging> </project>
- groupId : 组织标识，例如：org.codehaus.mojo，在M2_REPO目录下，将是: org/codehaus/mojo目录。
- artifactId : 项目名称，例如：my-project，在M2_REPO目录下，将是：org/codehaus/mojo/my-project目录。
- 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。
- 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>junit</groupId> <artifactId>junit</artifactId> <version>4.0</version> <scope>test</scope> </dependency> … </dependencies>
- groupId , artifactId , version :
- scope : compile(default),provided,runtime,test,system
- 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>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
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>4.0.0</modelVersion> <groupId>org.codehaus.mojo</groupId> <artifactId>my-parent</artifactId> <version>2.0</version> <modules> <module>my-project<module> </modules> </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${X}，可用于pom文件任何赋值的位置。有以下分类：
- env.X：操作系统环境变量，比如${env.PATH}
- project.x：pom文件中的属性，比如：<project><version>1.0</version></project>，引用方式：${project.version}
- settings.x：settings.xml文件中的属性，比如：<settings><offline>false</offline></settings>，引用方式：${settings.offline}
- Java System Properties：java.lang.System.getProperties()中的属性，比如java.home，引用方式：${java.home}
- 自定义：在pom文件中可以：<properties><installDir>c:/apps/cargo-installs</installDir></properties>，引用方式：${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"> … <!– "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>
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