How to view everything running on the event thread

We are experiencing a bug we cannot track down where something is freezing up our swing thread (it's been almost 2 weeks now and no real results) - we are experienced Swing programmers but we have 开发者_JS百科a huge program and believe it to be in some of the legacy code

I am wondering, is there any way outside of editing the actual EventQueue class in the JDK which will allow us to view all pieces of our code currently running on the Event Dispatch Thread - maybe some type of tool which will allow us to view things as they enter or leave the event dispatch thread?

One interesting approach is to extend EventQueue and push() it, as shown here.

Logging everything that passes through the Event Dispatch Thread seems a cumbersome way to diagnose a freeze. Wouldn't it be easier to wait until the problem occurs, and then ask the Event Dispatch Thread what it's doing now? One way to do this is to enable JMX monitoring, connect to your running process with a JMX client such a VisualVM (which ships with the JDK), wait for the problem to occur, and then take a thread dump.

In case you still wish to log everything the Event Dispatch Thread is doing, you can do this by:

1. In Eclipse, launch the application in debug mode.

2. Create a breakpoint on EventQueue.dispatchEvent, right-click it, select "properties", check "condition", and enter the following "condition":

   System.out.println(arg0);
   return false;
   

It might be good idea to try BTrace to instrument the EventQueue and capture stack traces each time something gets added. I think the latest VisualVM has plugins that will allow you to instrument a running JVM with a BTrace script.

If you're using the Oracle JRE, there is a TracedEventQueue included already. You can install it as mentioned before:

EventQueue eventQueue = Toolkit.getDefaultToolkit().getSystemEventQueue();
eventQueue.push(new TracedEventQueue());

Note, this will output a lot of output...