FULL PRODUCT VERSION :
java version "1.6.0_10-ea"
Java(TM) SE Runtime Environment (build 1.6.0_10-ea-b09)
Java HotSpot(TM) Client VM (build 11.0-b09, mixed mode, sharing)

The compiler is: javac 1.6.0_03

FULL OS VERSION :
Microsoft Windows XP [Version 5.1.2600]

A DESCRIPTION OF THE PROBLEM :
The gui thread invokes component's importData(), which invokes Transferable's getTransferData(). I do not see the debug trace right after the transferable invocation. I conclude that the thread terminates. But no exception stack traces are printed in the console.

THE PROBLEM WAS REPRODUCIBLE WITH -Xint FLAG: Yes

THE PROBLEM WAS REPRODUCIBLE WITH -server FLAG: Did not try

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
See source code below.

EXPECTED VERSUS ACTUAL BEHAVIOR :
Drag and Drop produces the following messages:

DEBUG1: dropping on 'Sample i'
DEBUG2: getTransferData(): The item to drop is 'Sample j'

The third message expected:

DEBUG3: got 'Sampe j'

is not shown.
REPRODUCIBILITY :
This bug can be reproduced always.

---------- BEGIN SOURCE ----------
Use console to compile and run:

import java.awt.event.*;
import java.awt.*;
import javax.swing.*;
import javax.swing.tree.*;
import javax.swing.filechooser.*;
import java.io.*;
import java.util.*;
import java.awt.datatransfer.*;
 
class SongTree extends JTree {
 
class Item extends DefaultMutableTreeNode {

Item(Object userObj) {
super(userObj);
}

void appendChild(Item item) {
((DefaultTreeModel)treeModel).insertNodeInto(item, this, getChildCount());
}

public void Drop(Object o) {
log("Some " + o + "-thing has dropped on me. Handling is not implemented.");
}

}

static void log(String msg) {
System.out.println(msg);
}

SongTree() {
super();
     Item top = new Item("root");
setModel(new DefaultTreeModel(top));
top.appendChild(new Item("Sample 1"));
top.appendChild(new Item("Sample 2"));
getSelectionModel().setSelectionMode(TreeSelectionModel.SINGLE_TREE_SELECTION);
setEditable(true);
setRootVisible(true);
     setDragEnabled(true);
     setDropMode(DropMode.ON_OR_INSERT);
     expandRow(0);
     setTransferHandler(new TransferHandler() {

public boolean importData(TransferSupport support) {
if (!canImport(support)) {
return false;
}

try {
Item target = (Item)((JTree.DropLocation)support.getDropLocation()).getPath().getLastPathComponent();
log("dropping on " + target + " DEBUG1"); // <- I SEE THIS
Object o = support.getTransferable().getTransferData(null);
log("dropping item " + o + " DEBUG3"); // <-- BUT CANNOT SEE THIS!!
target.Drop(o);
log("ok");
} catch (UnsupportedFlavorException e) {
log("ERROR " + e + " importing the data");
return false;
} catch (IOException e) {
log("ERROR " + e + " importing the data");
return false;
}
log("ok2");
return true;

}

public boolean canImport(TransferSupport support) {
JTree.DropLocation dropLocation = (JTree.DropLocation)support.getDropLocation();
if (!support.isDrop() || dropLocation.getPath() == null) {
return false;
}

Class transferrableRefClass = support.getDataFlavors()[0].getRepresentationClass();
log("ref is " + transferrableRefClass);
return true;//((Item) dropLocation.getPath().getLastPathComponent()).isMethodImplemented("Drop", new Class[] {transferrableRefClass});

}

public int getSourceActions(JComponent comp) {
log("getSourceActions");
return LINK; // COPY
}

public Transferable createTransferable(JComponent comp) {
final Object ref = getSelectionPath().getLastPathComponent();
log("createTransferable(" + (ref) + ")");

return new Transferable() {

final DataFlavor[] flavours = new DataFlavor[] {new DataFlavor(ref.getClass(), DataFlavor.javaJVMLocalObjectMimeType)};

public Object getTransferData(DataFlavor flavor) {
log("getTransferData. The item to drop is " + ref + " DEBUG2"); // <- I SEE THIS
return ref;
}

public DataFlavor[] getTransferDataFlavors() {log("getFlavours"); return flavours;}

public boolean isDataFlavorSupported (DataFlavor flavor) {
log("isFlavourSupported(" + flavor + ")");
return false; // this normally must not be called
}

};
}

});

} // TransferHandler

}
 
class JTreeTest {

public static void main(String[] args) {
        javax.swing.SwingUtilities.invokeLater(new Runnable() {
            public void run() {
final JFrame frame = new JFrame("JTreeTest");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

frame.getContentPane().add(new SongTree(), BorderLayout.CENTER);
frame.setPreferredSize(new Dimension(300, 300));

frame.pack();
frame.setVisible(true);
            }
        });
}
---------- END SOURCE ----------