开发自己的Maven插件之一:hello world

2012-07-02 18:19310人阅读评论(3)收藏举报

一直在使用Maven，用了各种各样的插件，但是有时候没有的话，还是需要自己写点。写一个插件并不难，会写插件的另一个好处就是了解了更多的Maven工作机制的内幕。对更好的使用Maven有帮助。

首先创建一个Maven项目，名叫plugin-example1。

这里要理解一个术语:mojo，就是Maven Plain Old Java Object,也就是一个普通的Java类。
我们需要mojo的api库，所以在pom.xml中添加一个依赖：

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1. <dependencies>
2. <dependency>
3. <groupId>org.apache.maven</groupId>
4. <artifactId>maven-plugin-api</artifactId>
5. <version>2.0</version>
6. </dependency>
7. </dependencies>

<dependencies> <dependency> <groupId>org.apache.maven</groupId> <artifactId>maven-plugin-api</artifactId> <version>2.0</version> </dependency> </dependencies>创建一个Example类，继承于AbstractMojo,实现execute方法。
代码很简单：

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1. public class Exampleextends AbstractMojo{
3. public void execute()throws MojoExecutionException, MojoFailureException {
4. getLog().info("Hello world");
5. }
7. }

public class Example extends AbstractMojo{ public void execute() throws MojoExecutionException, MojoFailureException { getLog().info("Hello world"); } }getLog()获取的是AbstractMojo内部的log，类型是：org.apache.maven.plugin.logging.Log;
至少在Mojo的开发中，不要使用其他的Log基础设施。

现在修改一下工程的描述信息：

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1. <groupId>org.freebird</groupId>
2. <artifactId>plugin-example1</artifactId>
3. <version>1.0-SNAPSHOT</version>
4. <packaging>maven-plugin</packaging>
6. <name>plugin-example1</name>
7. <url>http://maven.apache.org</url>
9. <properties>
10. <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
11. </properties>

<groupId>org.freebird</groupId> <artifactId>plugin-example1</artifactId> <version>1.0-SNAPSHOT</version> <packaging>maven-plugin</packaging> <name>plugin-example1</name> <url>http://maven.apache.org</url> <properties> <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding> </properties>
注意,packaging的值是maven-plugin

现在编译吧，很快就遇到错误：

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1. [ERROR] Failed to execute goal org.apache.maven.plugins:maven-plugin-plugin:2.9:descriptor (default-descriptor) on project plugin-example1: Error extracting plugin descriptor: 'No mojo definitions were found for plugin: org.freebird:plugin-example1.' -> [Help 1]
2. org.apache.maven.lifecycle.LifecycleExecutionException: Failed to execute goal org.apache.maven.plugins:maven-plugin-plugin:2.9:descriptor (default-descriptor) on project plugin-example1: Error extracting plugin descriptor: 'No mojo definitions were found for plugin: org.freebird:plugin-example1.'

[ERROR] Failed to execute goal org.apache.maven.plugins:maven-plugin-plugin:2.9:descriptor (default-descriptor) on project plugin-example1: Error extracting plugin descriptor: 'No mojo definitions were found for plugin: org.freebird:plugin-example1.' -> [Help 1]org.apache.maven.lifecycle.LifecycleExecutionException: Failed to execute goal org.apache.maven.plugins:maven-plugin-plugin:2.9:descriptor (default-descriptor) on project plugin-example1: Error extracting plugin descriptor: 'No mojo definitions were found for plugin: org.freebird:plugin-example1.'
需要加入一个maven-plugin-plugin来生成descriptor。不知道Maven的官方文档中为什么不提。

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1. <build>
2. <plugins>
3. <plugin>
4. <groupId>org.apache.maven.plugins</groupId>
5. <artifactId>maven-plugin-plugin</artifactId>
6. <version>3.0</version>
7. <executions>
8. </executions>
9. <configuration>
10. <!-- Needed for Java 5 annotation based configuration, for some reason. -->
11. <skipErrorNoDescriptorsFound>true</skipErrorNoDescriptorsFound>
12. </configuration>
13. </plugin>
14. </plugins>
15. </build>

<build> <plugins> <plugin> <groupId>org.apache.maven.plugins</groupId> <artifactId>maven-plugin-plugin</artifactId> <version>3.0</version> <executions> </executions> <configuration> <!-- Needed for Java 5 annotation based configuration, for some reason. --> <skipErrorNoDescriptorsFound>true</skipErrorNoDescriptorsFound> </configuration> </plugin> </plugins> </build>

这样编译就通过了。或者在类的注视上添加一个descriptor:

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1. /**
2. *
3. * @goal sayhi
4. */
5. public class Exampleextends AbstractMojo{

/** * * @goal sayhi */public class Example extends AbstractMojo{

 

为了将Maven部署在私服上，需要加上如下配置：

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1. <distributionManagement>
2. <snapshotRepository>
3. <id>snapshots</id>
4. <url>http://your_server:8080/nexus/content/repositories/snapshots</url>
5. </snapshotRepository>
6. </distributionManagement>

<distributionManagement> <snapshotRepository> <id>snapshots</id> <url>http://your_server:8080/nexus/content/repositories/snapshots</url> </snapshotRepository> </distributionManagement>
然后运行mvn clean package deploy

部署成功。