Thread of execution terminates silently on getting local transferable data

Question

I have the following class to drag and drop node references within a JTree:
     class MyTransferable implements Transferable {
          Item ref;
          final DataFlavor[] flavours = new DataFlavor[1];
          MyTransferable(Item i) {
               super();
               ref = i;
               flavours[0] = new DataFlavor(i.getClass(), DataFlavor.javaJVMLocalObjectMimeType);
               log("items flavour is " + flavours[0]);
          public Item getTransferData(DataFlavor flavor) {
               log("getTransferData. Returning " + ref); // *<-- I see this*
               return ref; // *<-- the procedure never returns*
          public DataFlavor[] getTransferDataFlavors() {log("getFlavours"); return flavours;} // try null
          public boolean isDataFlavorSupported (DataFlavor flavor) {log("isFlavourSupported(" + flavor + ")"); return false;}
     }In the importData(), I have the following code
     try {
          Node target = (Node)((JTree.DropLocation)support.getDropLocation()).getPath().getLastPathComponent();
          log("dropping on " + target); // *<-- I see this*
          Object o = support.getTransferable().getTransferData(null);
          log("dropping item " + o); // <- does not appear on the console
          target.Drop(o);
     } catch (UnsupportedFlavorException e) {
          log("ERROR " + e + " importing the data");
          return false;
     } catch (IOException e) {
          log("ERROR " + e + " importing the data");
          return false;
return true;The execution of the thread mysteriously ceases at the end of getTransferData(). No traces in the console. Yet, application does not fail and goes not reacting on graphic controls in normal way.Any ideas why and where the control jumps?
BTW, I have mentioned that DataFlavor.javaJVMLocalObjectMimeType) creates java.awt.datatransfer.DataFlavor[mimetype=application/x-java-[b]serialized-object;representationclass=SongTree$Pattern
Why does it serialize the local object, which is of type javaJVMLocalObjectMimeType and must be transferred by reference? Can be the problem because I try to gain access the serialized object?
Edited by: valjok on Jan 9, 2008 2:08 PM

Answer 1

Thank you for responding. I have double checked and assure you that the traces are produced by the code.
I have purified the code for you to reproduce. I 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 + " DEBUG"); // <-- 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);
}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)