编写 Java FTP 服务器

Question

我正在尝试编写一个代码，在我的独立设备上打开一个 FTP 服务器，这样我就可以将文件从它复制到另一台计算机上的客户端，反之亦然，但我对服务器端编程非常陌生，不会了解如何。

我得到了Apache FtpServer，但对它的使用有点困惑，我正在寻找如何使用它的基本步骤。可能是这样的：

1. 执行连接命令
2. 登录
3. 做一些事情....

Answer 1

让我为你写一个基本的例子，使用非常有用的Apache FtpServer：

FtpServerFactory serverFactory = new FtpServerFactory();
ListenerFactory factory = new ListenerFactory();
factory.setPort(1234);// set the port of the listener (choose your desired port, not 1234)
serverFactory.addListener("default", factory.createListener());
PropertiesUserManagerFactory userManagerFactory = new PropertiesUserManagerFactory();
userManagerFactory.setFile(new File("/home/blablah/myusers.properties"));//choose any. We're telling the FTP-server where to read its user list
userManagerFactory.setPasswordEncryptor(new PasswordEncryptor()
{//We store clear-text passwords in this example

        @Override
        public String encrypt(String password) {
            return password;
        }

        @Override
        public boolean matches(String passwordToCheck, String storedPassword) {
            return passwordToCheck.equals(storedPassword);
        }
    });
    //Let's add a user, since our myusers.properties file is empty on our first test run
    BaseUser user = new BaseUser();
    user.setName("test");
    user.setPassword("test");
    user.setHomeDirectory("/home/blablah");
    List<Authority> authorities = new ArrayList<Authority>();
    authorities.add(new WritePermission());
    user.setAuthorities(authorities);
    UserManager um = userManagerFactory.createUserManager();
    try
    {
        um.save(user);//Save the user to the user list on the filesystem
    }
    catch (FtpException e1)
    {
        //Deal with exception as you need
    }
    serverFactory.setUserManager(um);
    Map<String, Ftplet> m = new HashMap<String, Ftplet>();
    m.put("miaFtplet", new Ftplet()
    {

        @Override
        public void init(FtpletContext ftpletContext) throws FtpException {
            //System.out.println("init");
            //System.out.println("Thread #" + Thread.currentThread().getId());
        }

        @Override
        public void destroy() {
            //System.out.println("destroy");
            //System.out.println("Thread #" + Thread.currentThread().getId());
        }

        @Override
        public FtpletResult beforeCommand(FtpSession session, FtpRequest request) throws FtpException, IOException
        {
            //System.out.println("beforeCommand " + session.getUserArgument() + " : " + session.toString() + " | " + request.getArgument() + " : " + request.getCommand() + " : " + request.getRequestLine());
            //System.out.println("Thread #" + Thread.currentThread().getId());

            //do something
            return FtpletResult.DEFAULT;//...or return accordingly
        }

        @Override
        public FtpletResult afterCommand(FtpSession session, FtpRequest request, FtpReply reply) throws FtpException, IOException
        {
            //System.out.println("afterCommand " + session.getUserArgument() + " : " + session.toString() + " | " + request.getArgument() + " : " + request.getCommand() + " : " + request.getRequestLine() + " | " + reply.getMessage() + " : " + reply.toString());
            //System.out.println("Thread #" + Thread.currentThread().getId());

            //do something
            return FtpletResult.DEFAULT;//...or return accordingly
        }

        @Override
        public FtpletResult onConnect(FtpSession session) throws FtpException, IOException
        {
            //System.out.println("onConnect " + session.getUserArgument() + " : " + session.toString());
            //System.out.println("Thread #" + Thread.currentThread().getId());

            //do something
            return FtpletResult.DEFAULT;//...or return accordingly
        }

        @Override
        public FtpletResult onDisconnect(FtpSession session) throws FtpException, IOException
        {
            //System.out.println("onDisconnect " + session.getUserArgument() + " : " + session.toString());
            //System.out.println("Thread #" + Thread.currentThread().getId());

            //do something
            return FtpletResult.DEFAULT;//...or return accordingly
        }
    });
    serverFactory.setFtplets(m);
    //Map<String, Ftplet> mappa = serverFactory.getFtplets();
    //System.out.println(mappa.size());
    //System.out.println("Thread #" + Thread.currentThread().getId());
    //System.out.println(mappa.toString());
    FtpServer server = serverFactory.createServer();
    try
    {
        server.start();//Your FTP server starts listening for incoming FTP-connections, using the configuration options previously set
    }
    catch (FtpException ex)
    {
        //Deal with exception as you need
    }

请注意，在服务器端，您不必手动处理连接、登录等：Ftplet 会为您完成。

但是，您可以在匿名内部 Ftplet 类的重写方法中添加自定义的预处理[或后]处理（当您使用 new Ftplet(){ ... } 实例化它时。