Doing background task in Swing application

[Heatryn]

Hi everyone.

I have a client/server application in Swing. The clients sends a request via RMI to send an email to the server on another computer. However I want the server method to redirect directly to the client. Otherwise my Swing application will hang for some time.

I have done this with a SwingWorker thread and the doInBackground method.

	    emailThread = new SwingWorker<Boolean, Boolean>() {
		@Override
		protected Boolean doInBackground() throws Exception {
		    while (!this.isCancelled()) {
			if (emailQueue.size() > 0) {
			  //  log("Email versturen...");
			    emailQueue.get(0).send();
			    log("Email verstuurd naar " + emailQueue.get(0).getToAddresses().get(0) + " met als onderwerp " + emailQueue.get(0).getSubject());
			    emailQueue.remove(0);
			}
		    }
		    return true;
		}

	    };

I have a class variable with a queue of email messages. Everytime I call the method sendEmail, I just add another email to this queue variable. In the doInBackground method I check continuously if there are some emails in the queue and I send them and remove them afterwards from the queueu. You can see that in the above code.

This works fine. However there is the problem of performance. When I start the server my CPU usage at the server computer goes to 100% and slows everything down.

When I put however a Thread.sleep method in the while lus, I have the problem when I want to send 100 emails, that there is a time between every email. So that is not what I want.

How can I fix this?

[doWhile]

Look into how to use wait/notify. For instance, your worker can wait on the queue, which you can notify when an item is added to the queue. Alternatively, look into the BlockingQueue implementations.

[Heatryn]

Thank you!

Works like a charm.