请教怎么用java 程序启动Apache-ftpserver 功能

    FtpServerFactory serverFactory = new FtpServerFactory();   
        
        //监听   
        ListenerFactory factory = new ListenerFactory();   

        factory.setPort(2121);   

     
        serverFactory.addListener("default", factory.createListener());   
        PropertiesUserManagerFactory userManagerFactory = new PropertiesUserManagerFactory();   
        userManagerFactory.setFile(new File("D:/users.properties"));   
        /**使用自己的加密类,因为apache ftp server 使用的是md5 也就是logon之前需把密码加密后才能logon */  
  //      userManagerFactory.setPasswordEncryptor(new LocalPassword());   
        serverFactory.setUserManager(userManagerFactory.createUserManager());   
        //创建服务并启动   
        FtpServer server =   serverFactory.createServer();    
        try {   
         server.start();   
  } catch (FtpException e) {   
   e.printStackTrace();   
  }