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《Maven官方文檔》POM文件（一）
什麼是POM？
POM(project object model)包含了工程信息和工程的配置細節，Maven使用POM文件來構建工程。POM文件包含了工程中的大部分默認值。舉個例子，target是默認的構建目錄，src/main/java是默認的源碼目錄，src/test/java是默認的測試源碼目錄，等等。
Maven2中的pom.xml就是Maven1中的project.xml。相比於在maven.xml中包含可執行的goal，現在goals和plugins都可以在pom.xml中配置。當執行一個task或者goal時，Maven會在當前目錄下尋找並讀取pom.xml來獲取配置信息，然後執行goal。
能在pom.xml中聲明的配置包括工程依賴(project dependencies)，插件(plugins)，可執行的目標(goals)，構建配置(build profiles)等等。其他信息，比如工程版本，描述，開發者，郵件列表等等也可以在pox.xml中聲明。
Super POM
Super POM是Maven的默認POM文件，除非你顯示的聲明繼承關係，否則所有的POM文件都是在Super POM的基礎上的擴展，也就是說，Super POM中的的配置會被你的工程中創建的pom.xml繼承。Maven 2.0.x中的Super POM代碼如下：
<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>https://repo1.maven.org/maven2</url>
<snapshots>
<enabled>false</enabled>
</snapshots>
</repository>
</repositories>
<pluginRepositories>
<pluginRepository>
<id>central</id>
<name>Maven Plugin Repository</name>
<url>https://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>
下麵是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>https://repo1.maven.org/maven2</url>
<snapshots>
<enabled>false</enabled>
</snapshots>
</repository>
</repositories>
<pluginRepositories>
<pluginRepository>
<id>central</id>
<name>Maven Plugin Repository</name>
<url>https://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
一個最小化的POM文件的要求如下：
- project 標簽作為頂層標簽
- modelVersion – 應該設為4.0.0
- groupId – 工程開發組的唯一id
- artifactId – 工件(artifact)或工程(projrct)的唯一id
- version – 版本號
這裏是一個最小化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文件中需要聲明 groupId , artifactId 和 version 。這三個值以<groupId>:<artifactId>:<version>的形式聲明，它們組成了工程的完整名稱。比如上麵的例子，完整名稱為”com.mycompany.app:my-app1″。
如第一節所說，如果配置細節沒有顯示的設置，Maven將會使用繼承自Super POM默認配置。其中一個默認值就是包的類型(packaging type)，每個Maven工程都有一個包類型，如果沒有在POM中設置，則默認為”jar”。
前麵的Minimal POM中，其中 repositories 這個值沒有設置，如果你使用minimal POM來構建你的工程，它將使用繼承Super POM中的 repositories 值(https://repo.maven.apache.org/maven2)，當Maven在POM中找到依賴，它就會去這個地址下載依賴包。
最後更新：2017-05-19 16:38:00