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