开发自定义Maven2插件

原文：http://tianya23.blog.51cto.com/1081650/364121

一、创建一个插件项目 

    > mvn archetype:create -DgroupId=org.sonatype.mavenbook.plugins -DartifactId=first-maven-plugin -DarchetypeGroupId=org.apache.maven.archetypes -DarchetypeArtifactId=maven-archetype-mojo 

    maven会自动到远程库去下载maven-archetype-mojo的插件； 
    创建成功会生成一个first-maven-plugin的文件夹，里有一个pom.xml文件，内容： 

 <groupId>org.sonatype.mavenbook.plugins</groupId>
 <artifactId>first-maven-plugin</artifactId>
 <packaging>maven-plugin</packaging>
 <version>1.0 -SNAPSHOT</version>
 <name>first-maven-plugin Maven Mojo</name>
 <url>http://maven.apache.org</url>

 <dependencies>
     <dependency>
         <groupId>org.apache.maven</groupId>
         <artifactId>maven-plugin-api</artifactId>
         <version>2.0 </version>
     </dependency>
     <dependency>
         <groupId>junit</groupId>
         <artifactId>junit</artifactId>
         <version>3.8 . 1 </version>
         <scope>test</scope>
     </dependency>
 </dependencies>

二、创建一个MOJO 

   MOJO就是一个供插件调用处理的普通类。 

package org.sonatype.mavenbook.plugins;

import org.apache.maven.plugin.AbstractMojo;
import org.apache.maven.plugin.MojoExecutionException;
import org.apache.maven.plugin.MojoFailureException;

/**
* Echos an object string to the output screen.
*
* @goal echo
*/
public class EchoMojo extends AbstractMojo {
   /**
    * Any Object to print out.
    *
    * @parameter expression="${echo.message}"
    *                        default-value="Hello Maven World..."
    */
   private Object message;

   public void execute() throws MojoExecutionException, MojoFailureException {
    getLog().info(message.toString());
  }
}

创建了一个 EchoMojo 类，必须继承AbstractMojo类，实现execute方法，这个方法就是插件调用的入口； 

三、build, run自定义插件 

   > mvn clean install 
   插件运行遵循groupId:artifactId:version:goal格式； 
   >  mvn org.sonatype.mavenbook.plugins:first-maven-plugin:1.0-SNAPSHOT:echo -Decho.message="The Eagle has Landed"  

D:\code\first-maven-plugin>mvn org.sonatype.mavenbook.plugins:first-maven-plugin:1.0-SNAPSHOT:echo -Decho.message="The Eagle has Landed"
[INFO] Scanning for projects...
[INFO] ------------------------------------------------------------------------
[INFO] Building first-maven-plugin Maven Mojo
[INFO]        task-segment: [org.sonatype.mavenbook.plugins:first-maven-plugin:1.0-SNAPSHOT:echo]
[INFO] ------------------------------------------------------------------------
[INFO] [first:echo {execution: default-cli}]
[INFO] The Eagle has Landed
[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESSFUL
[INFO] ------------------------------------------------------------------------
[INFO] Total time: < 1 second
[INFO] Finished at: Sat Jul 31 14:26:50 CST 2010
[INFO] Final Memory: 1M/4M
[INFO] ------------------------------------------------------------------------

上面命令中，出来一个echo，这个就是goal，在 EchoMojo 类里用注释定义@goal echo； 可能上面的命令太长，怎样做到像archetype:create一样写法？可以定义前缀; 

四、定义前缀 
   在setting.xml文件加： 

 <pluginGroups>
   <pluginGroup>org.sonatype.mavenbook.plugins</pluginGroup>
 </pluginGroups>

然后： 
    > mvn first:echo -Decho.message="My first Maven plugin" 
非常简单。 
如果插件的artifactId遵循maven-first-plugin，或者first-maven-plugin模式。Maven就会自动为你的插件赋予前缀first。 
${prefix}-maven-plugin, OR maven-${prefix}-plugin 
也可自定义前缀，在pom.xml加： 

 <build>
   <plugins>
     <plugin>
       <artifactId>first-maven-plugin</artifactId>
       <version>2.3 </version>
       <configuration>
         <goalPrefix>first</goalPrefix>
       </configuration>
     </plugin>
   </plugins>
 </build>