需要帮助来改善Java客户端端口侦听器

Question

我有一小段代码在包含SWING控件的applet中运行，用于将信息写入某个端口上的套接字，然后侦听响应。这可以正常工作，但是有问题。端口侦听器实际上处于循环状态，直到服务器接收到null。我希望用户能够在等待服务器响应的同时在applet实例化的GUI中执行其他操作（这可能需要几分钟的时间）。我还需要担心服务器与客户端之间的连接断开。但是在编写代码的方式中，小程序似乎冻结（实际上是在循环中），直到服务器做出响应。如何允许侦听器在后台进行侦听，从而允许程序中发生其他事情。我认为我需要使用线程，而我
当然对于此应用程序，它很容易实现，但是我缺乏扎实的线程基础阻碍了我的工作。下面是代码（您可以看到它很简单）。我如何改进它以使其能够执行我需要做的事情>

  public String writePacket(String packet) {
/* This method writes the packet to the port - established earlier */
   System.out.println("writing out this packet->"+packet+"<-");
   out.println(packet);
  String thePacket =    readPacket();  //where the port listener is invoked.  
   return thePacket;
   }
    private String readPacket() {
      String thePacket ="";
      String fromServer="";
      //Below is the loop that freezes everything.   
     try {
      while ((fromServer = in.readLine()) != null) { 
        if (thePacket.equals("")) thePacket = fromServer;
        else 
        thePacket = thePacket+newLine+fromServer;
    }
        return thePacket;  //when this happens, all listening should stop.   
   } catch (IOException e) {
        // TODO Auto-generated catch block
    e.printStackTrace();
    return null;
    }

     }

谢谢，

艾略特

Answer 1

有很多不同的方法可以使IO在不同的线程上执行，但是在这种情况下，您可能要使用SwingWorker。

您的代码如下所示：

private final Executor executor = Executors.newSingleThreadExecutor();

public void writePacket(final String packet) 
{
  // schedules execution on the single thread of the executor (so only one background operation can happen at once)
  //
  executor.execute(new SwingWorker<String, Void>()
      {

        @Override
        protected String doInBackground() throws Exception
        {
          // called on a background thread


          /* This method writes the packet to the port - established earlier */
          System.out.println("writing out this packet->"+packet+"<-");
          System.out.println(packet);
          String thePacket = readPacket();  //where the port listener is invoked.  
          return thePacket;            
        }

        @Override
        protected void done()
        {
          // called on the Swing event dispatch thread


          try
          {
            final String thePacket = get();

            // update GUI with 'thePacket'
          }
          catch (final InterruptedException e)
          {
            // TODO Auto-generated catch block
            e.printStackTrace();
          }
          catch (final ExecutionException e)
          {
            // TODO Auto-generated catch block
            e.printStackTrace();
          } 
        }
      });
}

private String readPacket() 
{
  String thePacket ="";
  String fromServer="";
  //Below is the loop that freezes everything.   
  try 
  {
    while ((fromServer = in.readLine()) != null) 
    { 
      if (thePacket.equals("")) 
        thePacket = fromServer;
      else 
        thePacket = thePacket+newLine+fromServer;
    }
    return thePacket;  //when this happens, all listening should stop.   
  } 
  catch (IOException e) 
  {
    e.printStackTrace();
    return null;
  }
}