maven的超级pom

对于 Maven3，超级 POM 在文件 %MAVEN_HOME%/lib/maven-model-builder-x.x.x.jar 中的 org/apache/maven/model/pom-4.0.0.xml 路径下、

对于 Maven2，超级 POM 在文件 %MAVEN_HOME%/lib/maven-x.x.x-uber.jar 中的 org/apache/maven/project/pom-4.0.0.xml 目录下。

这里的 x.x.x 表示 Maven 的具体版本。

对于使用java的人而言，继承这个词大家应该都不陌生。要继承pom就需要有一个父pom，在Maven中定义了超级pom.xml，任何没有申明自己父pom.xml的pom.xml都将默认继承自这个超级pom.xml。

       先来看一下这个超级pom.xml的定义：

Xml代码  

1. <project>  
2.   <modelVersion>4.0.0</modelVersion>  
3.   <name>Maven Default Project</name>  
4.    
5.   <repositories>  
6.     <repository>  
7.       <id>central</id>  
8.       <name>Maven Repository Switchboard</name>  
9.       <layout>default</layout>  
10.       <url>http://repo1.maven.org/maven2</url>  
11.       <snapshots>  
12.         <enabled>false</enabled>  
13.       </snapshots>  
14.     </repository>  
15.   </repositories>  
16.    
17.   <pluginRepositories>  
18.     <pluginRepository>  
19.       <id>central</id>  
20.       <name>Maven Plugin Repository</name>  
21.       <url>http://repo1.maven.org/maven2</url>  
22.       <layout>default</layout>  
23.       <snapshots>  
24.         <enabled>false</enabled>  
25.       </snapshots>  
26.       <releases>  
27.         <updatePolicy>never</updatePolicy>  
28.       </releases>  
29.     </pluginRepository>  
30.   </pluginRepositories>  
31.    
32.   <build>  
33.     <directory>${project.basedir}/target</directory>  
34.     <outputDirectory>${project.build.directory}/classes</outputDirectory>  
35.     <finalName>${project.artifactId}-${project.version}</finalName>  
36.     <testOutputDirectory>${project.build.directory}/test-classes</testOutputDirectory>  
37.     <sourceDirectory>${project.basedir}/src/main/java</sourceDirectory>  
38.     <!-- TODO: MNG-3731 maven-plugin-tools-api < 2.4.4 expect this to be relative... -->  
39.     <scriptSourceDirectory>src/main/scripts</scriptSourceDirectory>  
40.     <testSourceDirectory>${project.basedir}/src/test/java</testSourceDirectory>  
41.     <resources>  
42.       <resource>  
43.         <directory>${project.basedir}/src/main/resources</directory>  
44.       </resource>  
45.     </resources>  
46.     <testResources>  
47.       <testResource>  
48.         <directory>${project.basedir}/src/test/resources</directory>  
49.       </testResource>  
50.     </testResources>  
51.    <pluginManagement>  
52.        <plugins>  
53.          <plugin>  
54.            <artifactId>maven-antrun-plugin</artifactId>  
55.            <version>1.3</version>  
56.          </plugin>        
57.          <plugin>  
58.            <artifactId>maven-assembly-plugin</artifactId>  
59.            <version>2.2-beta-2</version>  
60.          </plugin>          
61.          <plugin>  
62.            <artifactId>maven-clean-plugin</artifactId>  
63.            <version>2.2</version>  
64.          </plugin>  
65.          <plugin>  
66.            <artifactId>maven-compiler-plugin</artifactId>  
67.            <version>2.0.2</version>  
68.          </plugin>  
69.          <plugin>  
70.            <artifactId>maven-dependency-plugin</artifactId>  
71.            <version>2.0</version>  
72.          </plugin>  
73.          <plugin>  
74.            <artifactId>maven-deploy-plugin</artifactId>  
75.            <version>2.4</version>  
76.          </plugin>  
77.          <plugin>  
78.            <artifactId>maven-ear-plugin</artifactId>  
79.            <version>2.3.1</version>  
80.          </plugin>  
81.          <plugin>  
82.            <artifactId>maven-ejb-plugin</artifactId>  
83.            <version>2.1</version>  
84.          </plugin>  
85.          <plugin>  
86.            <artifactId>maven-install-plugin</artifactId>  
87.            <version>2.2</version>  
88.          </plugin>  
89.          <plugin>  
90.            <artifactId>maven-jar-plugin</artifactId>  
91.            <version>2.2</version>  
92.          </plugin>  
93.          <plugin>  
94.            <artifactId>maven-javadoc-plugin</artifactId>  
95.            <version>2.5</version>  
96.          </plugin>  
97.          <plugin>  
98.            <artifactId>maven-plugin-plugin</artifactId>  
99.            <version>2.4.3</version>  
100.          </plugin>  
101.          <plugin>  
102.            <artifactId>maven-rar-plugin</artifactId>  
103.            <version>2.2</version>  
104.          </plugin>         
105.          <plugin>                 
106.            <artifactId>maven-release-plugin</artifactId>  
107.            <version>2.0-beta-8</version>  
108.          </plugin>  
109.          <plugin>                  
110.            <artifactId>maven-resources-plugin</artifactId>  
111.            <version>2.3</version>  
112.          </plugin>  
113.          <plugin>  
114.            <artifactId>maven-site-plugin</artifactId>  
115.            <version>2.0-beta-7</version>  
116.          </plugin>  
117.          <plugin>  
118.            <artifactId>maven-source-plugin</artifactId>  
119.            <version>2.0.4</version>  
120.          </plugin>          
121.          <plugin>  
122.             <artifactId>maven-surefire-plugin</artifactId>  
123.             <version>2.4.3</version>  
124.          </plugin>  
125.          <plugin>  
126.            <artifactId>maven-war-plugin</artifactId>  
127.            <version>2.1-alpha-2</version>  
128.          </plugin>  
129.        </plugins>  
130.      </pluginManagement>  
131.   </build>  
132.    
133.   <reporting>  
134.     <outputDirectory>${project.build.directory}/site</outputDirectory>  
135.   </reporting>  
136.   <profiles>  
137.     <profile>  
138.       <id>release-profile</id>  
139.    
140.       <activation>  
141.         <property>  
142.           <name>performRelease</name>  
143.           <value>true</value>  
144.         </property>  
145.       </activation>  
146.    
147.       <build>  
148.         <plugins>  
149.           <plugin>  
150.             <inherited>true</inherited>  
151.             <groupId>org.apache.maven.plugins</groupId>  
152.             <artifactId>maven-source-plugin</artifactId>  
153.             <executions>  
154.               <execution>  
155.                 <id>attach-sources</id>  
156.                 <goals>  
157.                   <goal>jar</goal>  
158.                 </goals>  
159.               </execution>  
160.             </executions>  
161.           </plugin>  
162.           <plugin>  
163.             <inherited>true</inherited>  
164.             <groupId>org.apache.maven.plugins</groupId>  
165.             <artifactId>maven-javadoc-plugin</artifactId>  
166.             <executions>  
167.               <execution>  
168.                 <id>attach-javadocs</id>  
169.                 <goals>  
170.                   <goal>jar</goal>  
171.                 </goals>  
172.               </execution>  
173.             </executions>  
174.           </plugin>  
175.           <plugin>  
176.             <inherited>true</inherited>  
177.             <groupId>org.apache.maven.plugins</groupId>  
178.             <artifactId>maven-deploy-plugin</artifactId>  
179.             <configuration>  
180.               <updateReleaseInfo>true</updateReleaseInfo>  
181.             </configuration>  
182.           </plugin>  
183.         </plugins>  
184.       </build>  
185.     </profile>  
186.   </profiles>  
187.    
188. </project>  

       对于一个pom.xml来说有几个元素是必须定义的，一个是project根元素，然后就是它里面的modelVersion、groupId、artifactId和version。由上面的超级pom.xml的内容我们可以看到pom.xml中没有groupId、artifactId和version的定义，所以我们在建立自己的pom.xml的时候就需要定义这三个元素。和java里面的继承类似，子pom.xml会完全继承父pom.xml中所有的元素，而且对于相同的元素，一般子pom.xml中的会覆盖父pom.xml中的元素，但是有几个特殊的元素它们会进行合并而不是覆盖。这些特殊的元素是：

Ø  dependencies

Ø  developers

Ø  contributors

Ø  plugin列表，包括plugin下面的reports

Ø  resources

参考：

1、http://blog.csdn.net/tounaobun/article/details/8958125

2、http://blog.csdn.net/haojiahj/article/details/49964919