pom.xml详解
一、什么是POM
ProjectObjectModel,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>
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(dependencylist)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
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:developersandcontributors、pluginlists、reportslists、pluginexecutionswithmatchingids、pluginconfiguration):
[...] <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:
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${X},可用于pom文件任何赋值的位置。有以下分类:
1.env.X:操作系统环境变量,比如${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.JavaSystemProperties: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}
[b]4、构建设置[/b]
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>