maven插件开发

最近开发代码生成相关的工具使用了maven插件开发方式

1. 添加依赖

<!--maven插件必须的-->
<packaging>maven-plugin</packaging>

<!--maven plugin必须-->
<dependency>
    <groupId>org.apache.maven</groupId>
    <artifactId>maven-plugin-api</artifactId>
    <version>3.8.4</version>
    <scope>provided</scope>
</dependency>
<!--maven plugin jdk5 之后支持注解-->
<dependency>
    <groupId>org.apache.maven.plugin-tools</groupId>
    <artifactId>maven-plugin-annotations</artifactId>
    <version>3.6.2</version>
    <scope>provided</scope>
</dependency>

<!--插件版本用新的，老版本会报错-->
<plugin>
    <groupId>org.apache.maven.plugins</groupId>
    <artifactId>maven-plugin-plugin</artifactId>
    <version>3.6.4</version>
</plugin>

注意
packing必须为maven-plugin, artifactId建议以maven-plugin结尾

2. 代码示例

@Mojo(name = "sayhi", threadSafe = true)
public class HelloMojo extends AbstractMojo {

    /**
     * 参数定义
     */
    @Parameter(property = "sayhi.greeting", defaultValue = "hello world")
    private String greeting;

    /**
     * @parameter
     */
    @Parameter(property = "outputDir", defaultValue = "D:/temp")
    private String outputDir;

    @Parameter(property = "projectDir", defaultValue = "${project.baseDir}")
    private String projectDir;

    @Override
    public void execute() throws MojoExecutionException, MojoFailureException {
        getLog().info("hello world.");
        getLog().info(greeting);

        // 相对路径
        File outputDirFile = new File(this.outputDir);
        getLog().info(outputDirFile.getAbsolutePath());
        getLog().info("projectDir:" + projectDir);
        try {
            ClassLoader classLoader = getClassLoader();
            String path = "D:/work_code/xxx_code/xxx-service/xxx/target/classes";
            Path clientPath = Paths.get(path, "/cn/xxx/xxx/xxx/xxx/mapper");
            scanDir(clientPath, classLoader);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    private void scanDir(Path clientPath, ClassLoader classLoader) throws Exception {
        Files.list(clientPath).forEach(p -> {
            try {
                String filePath = p.toString();
                // class文件路径
                String clsPath = filePath.substring(filePath.indexOf("classes") + 8);
                clsPath = clsPath.replace("\\", ".").replace(".class", "");
                Class<?> aClass = classLoader.loadClass(clsPath);
                Method[] methods = aClass.getMethods();
                getLog().info("method size:" + methods.length);
            } catch (Exception e) {
                e.printStackTrace();
            }
        });
    }

    private ClassLoader getClassLoader() throws Exception {
        String path = "D:/work_code/xxx_code/xxx-service/xxx/target/classes";
        String appPath = "D:/work_code/xxx_code/xxx-service/xxx/target/classes";
        URL url = new File(path).toURI().toURL();
        URL appUrl = new File(appPath).toURI().toURL();
        return new URLClassLoader(new URL[]{url, appUrl}, Thread.currentThread().getContextClassLoader());
    }

    public String getGreeting() {
        return greeting;
    }

    public void setGreeting(String greeting) {
        this.greeting = greeting;
    }

    public String getOutputDir() {
        return outputDir;
    }

    public void setOutputDir(String outputDir) {
        this.outputDir = outputDir;
    }

    public String getProjectDir() {
        return projectDir;
    }

    public void setProjectDir(String projectDir) {
        this.projectDir = projectDir;
    }
}

开发步骤

• 自己的类(入口)继承AbstractMojo
• 主类(入口)上添加注解@Mojo(name = "sayhi", threadSafe = true)，name自定义
• 定义参数，@Parameter标识，参数设置属性和默认值等，参数定义好后可以在插件中配置后使用
• 打包 mvn clean install
• 其他项目中使用mvn packageName:name-maven-plugin:version:mojoName<br/>验证

3. 遇到的坑

主要是ClassLoader加载路径时加载不到class文件，原因是定义URL时，使用==file://==开头，后面改为URL url = new File(path).toURI().toURL()即可

4. 2种启动方式及调试

1. 命令方式

   mvn packageName:pluginName:version:mojoName

2. 插件点击方式
   
   debug
   

参考

插件官网
mybatis-plus插件示例