Java background server class that might be called from ui thread

Question

I have a server communicating over network interface. This server should run on a background thread, so that it does not block the ui thread. The ui thread starts and stops the server. Even starting and stopping should be done from a background thread.

Currently I wrap all public methods of the server class in a thread that gets started immediately:

class Server {

  public void start() {
    new Thread() {
      public void run() {
        handleStart();
      }
    }.start();
  }

  public void stop() {
    new Thread() {
      public void run() {
        handleStop();
      }
    }.start(); 
  }

  private void handleStart() {
    startLooperThread();
  }

  private void handleStop() {
    stopLooperThread();
  }
}

Is this the proper way to do this or are there any neat alternatives provided by JDK (or any other library)?

Answer 1

Disclaimer: This answer uses the lambda-feature for java 8. Assuming non-availability of java 8, the expressions can be easily converted to Runnables.

You're completely overexerting yourself. Use inbuilt features of Java with a little composition and your server becomes by far easier:

public class Server {
     private final ExecutorService threadPool = Executors.newFixedThreadPool(1);

     public Server() {}

     public void start() {
         threadPool.execute(() -> handleStart()); //Runnable
     }

     public void stop() {
         threadPool.execute(() -> handleStop());
         threadPool.shutdown(); //depends a little on your functionality
     }
     //rest can remain unchanged
}

The Thread-Pool can be expanded manually. Additionally I'd recommend to override finalize() to shut down your executor.

Answer 2

What you have done is not the ideal way. For UI applications that generate events processed by a "Server", there are established design patterns. One such pattern is the "Event loop" or the "Scheduler queue". Goes something like this (In a pseudo-Java like language that is not quite verbose):

UI:

void onSomeUIEvent(UIEvent ev) {
    ServerContext.pushEvent(ev);
}

ServerContext:

static void pushEvent(UIEvent ev) {
    _blockingQueue.push(ev);
}

Server:

class Server {

    private BlockingQueue<UIEvent> _blockingQueue; //Shared with ServerContext
    Thread worker {
        void run() {
            UIEvent e = _blockingQueue.pop();
            //Now do something with the event, like start/stop something

        }
    }
}