Class not found when using SwingUtilities.invokeLater in OSGi Bundle

Question

(EDIT: Problem is solved - see details at the end)

I want to create a Swing JFrame with a WindowAdapter in an OSGi Bundle. When I do this using SwingUtilities.invokeLater, the WindowAdapter class is not found. Without invokeLater it works.

What do I need to do so that WindowAdapter is found when using invokeLater? Is invokeLater inappropriate in an OSGi environment?

The details:

I start an Apache Felix framework instance with my custom launcher, install the bundle and start it. My bundle's start method looks like this:

public void start(BundleContext arg0) throws Exception {
    myFrame = new MyFrame();
    myFrame.open();
}

This is the MyFrame class:

public class MyFrame {
    JFrame mainFrame;

    public void open() {
        SwingUtilities.invokeLater(new Runnable() {
            @Override
            public void run() {
                openImpl();
            }
        });
        // If called like this it works:
        // openImpl();
    }

    public void openImpl() {
        mainFrame = new JFrame("Title");
        mainFrame.setDefaultCloseOperation(WindowConstants.DO_NOTHING_ON_CLOSE);
        WindowAdapter wa = new WindowAdapter() {
        };
        mainFrame.addWindowListener(wa);
        mainFrame.setSize(800, 600);
        mainFrame.setLocationRelativeTo(null);
        mainFrame.setVisible(true);
    }
}

This is my manifest for the bundle:

Manifest-Version: 1.0
Ant-Version: Apache Ant 1.8.2
Created-By: 1.7.0_03-b05 (Oracle Corporation)
Built-By: Rainer Schwarze
Bundle-Name: DummyBdl
Bundle-Description: Dummy Bundle
Bundle-Vendor: admaDIC
Bundle-Version: 0.0.1
Bundle-Activator: dummybdl.Activator
Import-Package: org.osgi.framework, javax.swing
Export-Package: dummybdl.api
Export-Service: dummybdl.Provider

And this is the stack trace which I get:

Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
    at org.apache.felix.framework.BundleWiringImpl.findClassOrResourceByDelegation(BundleWiringImpl.java:1432)
    at org.apache.felix.framework.BundleWiringImpl.access$400(BundleWiringImpl.java:72)
    at org.apache.felix.framework.BundleWiringImpl$BundleClassLoader.loadClass(BundleWiringImpl.java:1843)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:356)
    at dummybdl.MyFrame.openImpl(MyFrame.java:24)
    at dummybdl.MyFrame$1.run(MyFrame.java:16)
    at java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:251)
    at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:705)
    at java.awt.EventQueue.access$000(EventQueue.java:101)
    at java.awt.EventQueue$3.run(EventQueue.java:666)
    at java.awt.EventQueue$3.run(EventQueue.java:664)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76)
    at java.awt.EventQueue.dispatchEvent(EventQueue.java:675)
    at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:211)
    at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:128)
    at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:117)
    at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:113)
    at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:105)
    at java.awt.EventDispatchThread.run(EventDispatchThread.java:90)

Being an OSGi newbie I tried several things to fix it, but couldn't find a solution so far. So why not make my first question at StackOverflow :-)

EDIT:

After debugging for half an hour it turns out that the problem was entirely mine: My code stopped the OSGi framework before openImpl gets called in the EDT.

So the Apache Felix framework marked the BundleWiringImpl instance (see stack trace) as disposed. When my openImpl gets called in the EDT, BundleWiringImpl.getClassLoader returns null because it is marked as disposed. Eventually this leads to the NPE. (I should have gone the extra steps of posting the 50 lines of my Felix loader which might have made the error obvious.)

Answer 1

My code stopped the OSGi framework before openImpl gets called in the EDT.

Without invokeLater openImpl is called immediately and before my other code shuts down the OSGi framework. With invokeLater the call to openImpl is scheduled for later and before that "later" happens, my code shuts down the OSGi framework.

In that case the Apache Felix framework marked the BundleWiringImpl instance (see stack trace) as disposed. When my openImpl gets called in the EDT, BundleWiringImpl.getClassLoader returns null because it is marked as disposed. Eventually this leads to the NPE.