We are investigating the following exception which occurs in the drop phase of a D'n'D operation.

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java.io.IOException: com.nortel.cpt.gui.dnd.TemplateItem
        at sun.awt.datatransfer.TransferableProxy.getTransferData(TransferableProxy
.java:61)
        at java.awt.dnd.DropTargetContext$TransferableProxy.getTransferData(DropTar
getContext.java:359)
        at com.nortel.cpt.gui.dnd.DropTree.drop(DropTree.java:270)
        at java.awt.dnd.DropTarget.drop(DropTarget.java:404)
        at sun.awt.dnd.SunDropTargetContextPeer.processDropMessage(SunDropTargetCon
textPeer.java:547)
        at sun.awt.dnd.SunDropTargetContextPeer.access$800(SunDropTargetContextPeer
.java:52)
        at sun.awt.dnd.SunDropTargetContextPeer$EventDispatcher.dispatchDropEvent(S
unDropTargetContextPeer.java:806)
        at sun.awt.dnd.SunDropTargetContextPeer$EventDispatcher.dispatchEvent(SunDr
opTargetContextPeer.java:744)
        at sun.awt.dnd.SunDropTargetEvent.dispatch(SunDropTargetEvent.java:29)
        at java.awt.Component.dispatchEventImpl(Component.java:3456)
        at java.awt.Container.dispatchEventImpl(Container.java:1623)
        at java.awt.Component.dispatchEvent(Component.java:3439)
        at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:3450)
        at java.awt.LightweightDispatcher.processDropTargetEvent(Container.java:323
6)
        at java.awt.LightweightDispatcher.dispatchEvent(Container.java:3090)
        at java.awt.Container.dispatchEventImpl(Container.java:1609)
        at java.awt.Window.dispatchEventImpl(Window.java:1585)
        at java.awt.Component.dispatchEvent(Component.java:3439)
        at java.awt.EventQueue.dispatchEvent(EventQueue.java:450)
        at com.nortel.inmP.commonuiP.swingP.GUIBlockerC.dispatchEvent(GUIBlockerC.j
ava:207)
        at java.awt.EventDispatchThread.pumpOneEventForHierarchy(EventDispatchThrea
d.java:197)
        at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.
java:150)
        at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:144)
        at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:136)
        at java.awt.EventDispatchThread.run(EventDispatchThread.java:99)

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This exception only occurs when the transfer object "TemplateItem" (and the DataFlavour) are not in the classpath but have been loaded by a user class loader (URLClassLoader). In our environment, most classes are loaded this way - the system and bootstrap loaders are not busy. The problem can be easily seen in the following decompiled code from

sun.awt.datatransfer.TransferableProxy:

    public Object getTransferData(DataFlavor dataflavor)
        throws UnsupportedFlavorException, IOException
    {
        Object obj = transferable.getTransferData(dataflavor);
        if(obj != null && isLocal &&
dataflavor.isFlavorSerializedObjectType())
        {
            ByteArrayOutputStream bytearrayoutputstream = new
ByteArrayOutputStream();
            (new
ObjectOutputStream(bytearrayoutputstream)).writeObject(obj);
            ByteArrayInputStream bytearrayinputstream = new
ByteArrayInputStream(bytearrayoutputstream.toByteArray());
            try
            {
                obj = (new
ObjectInputStream(bytearrayinputstream)).readObject();
            }
            catch(ClassNotFoundException classnotfoundexception)
            {
                throw new IOException(classnotfoundexception.getMessage());

            }
        }
        return obj;
    }

In this method, the transfer object obj is being serialized and deserialized. In the deserialization step, the classloader present in obj or dataflavor is not used (and it should be) to recreate obj. When the classloader in obj is different than the classloader in the ObjectInputStream, this code will not work.