CODEWITHSUNDEEP
javagwtinfinite-loopgxtgwt-2.5
Muhammad Gelbana
Muhammad Gelbana

Reputation: 4000

GWT application freezes due to an internal infinite loop

I'm running a GWT application using GWT 2.5.1 and Ext GWT v2.2.4 on Eclipse Juno. Java 6 (32 bit) and I can't change any of this.

I was recently handed over this application which is working fine on another machine. After starting the application (Run > GWT Application), I proceed with logging into my application, my code executes normally but then my app freezes. I debugged and found that the applications enters an infinite loop in this GWT internal method (i.e. in class com.google.gwt.dev.shell.BrowserChannelServer):

public void reactToMessages(SessionHandlerServer handler) {
    do {
      try {
        getStreamToOtherSide().flush();
        MessageType messageType = Message.readMessageType(
            getStreamFromOtherSide());
        switch (messageType) {
          case FREE_VALUE:
            final FreeMessage freeMsg = FreeMessage.receive(this);
            handler.freeValue(this, freeMsg.getIds());
            break;
          case INVOKE: //<<<< Keeps getting into this block
            InvokeOnServerMessage imsg = InvokeOnServerMessage.receive(this);
            ExceptionOrReturnValue result = handler.invoke(this, imsg.getThis(),
                imsg.getMethodDispatchId(), imsg.getArgs());
            sendFreedValues();
            ReturnMessage.send(this, result);
            break;
          case INVOKE_SPECIAL:
            handleInvokeSpecial(handler);
            break;
          case QUIT:
            return;
          default:
            throw new RemoteDeathError(new BrowserChannelException(
                "Invalid message type " + messageType));
        }
      } catch (IOException e) {
        throw new RemoteDeathError(e);
      } catch (BrowserChannelException e) {
        throw new RemoteDeathError(e);
      }
    } while (true);
}

messageType is always INVOKE and since the while condition is true, the loop never ends. So the execution is stuck at this stack:

Daemon Thread [Code server for av.mymodule from Mozilla/5.0 (Windows NT 6.1; WOW64; rv:26.0) Gecko/20100101 Firefox/26.0 on http://127.0.0.1:8889/mymodule.html?gwt.codesvr=127.0.0.1:9997 @ tsb2t8vtLUT/vrj#] (Suspended)
            BrowserChannelServer.reactToMessages(BrowserChannelServer$SessionHandlerServer) line: 292      
            BrowserChannelServer.processConnection() line: 547  
            BrowserChannelServer.run() line: 364  
            Thread.run() line: 662

I cleaned the project, deleted cache files, tmp files, recompiled numerous times, tried older version 2.4.0, but I can't try 2.6 because I'll need java 7 which I can't install at the moment. I tried chrome and firefox, same results. After some search I found some suggestions that I should not zoom in using the browser, however, and I'm not doing that.

What could be the problem please ?

Upvotes: 0

Views: 636

Answers (2)

Muhammad Gelbana
Muhammad Gelbana

Reputation: 4000

The problem was that Ext GWT 2.2.4 isn't compatible with GWT 2.5.1, but it's compatible with GWT 2.5.0

So using GWT 2.5.0 instead, solved the problem.

Upvotes: 1

Cataclysm
Cataclysm

Reputation: 8548

I think your while condition should be dynamic variable instead of using true. You should break out of do while loop. If not , your execution may stack.

public class TestDoWhile {
private static TestDoWhile test;

public static void main(final String[] args) {
    test = new TestDoWhile();
    test.invokeMethod(2);
    test.invokeMethod(1);
}
public final void invokeMethod(final int testCase) {
    do {
        switch (testCase) {
        case 1:
            System.out.println("Invoke");
            break;
        case 2:
            System.out.println("Please , let me quit !");
            return;
        default:
            return;
        }
    } while (true);
}
}

What is result of my java program ? That may stack. And I can't imagine your these two methods sendFreedValues(); ReturnMessage.send(this, result);

So, Add return instead of break . Have some useful for you.

Upvotes: 0

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