import java.awt.*;
import java.awt.event.*;
import java.awt.dnd.*;
import java.awt.datatransfer.*;
import javax.swing.event.*;
import javax.swing.*;
import java.io.*;
import java.util.*;
public class BugDndDeadlock
{
public static void main(String argv[])
{
// Display the Description
for(int i=0; i<desc.length; i++)
System.out.println(desc[i]);
Frame frame = new Frame("Java-2 Drag/Drop Deadlock Bug");
BugDndDeadlock c = new BugDndDeadlock(frame);
}
private static final String desc[] =
{
"Usage: java BugDndDeadlock",
" This test demonstrates a deadlock problem in Java-2 Drag-Drop.",
" Just drag text from one label to another and a deadlock will occur.",
" The deadlock is caused by the Label calling setCursor in MOUSE_MOVED",
" and can be avoided by removing the call to setCursor."
};
public BugDndDeadlock(Frame f)
{
DraggableLabel north = new DraggableLabel("One");
DraggableLabel south = new DraggableLabel("Two");
DraggableLabel east = new DraggableLabel("Three");
DraggableLabel west = new DraggableLabel("Four");
f.add (north, BorderLayout.NORTH);
f.add (south, BorderLayout.SOUTH);
f.add (east, BorderLayout.EAST);
f.add (west, BorderLayout.WEST);
f.setBounds (200, 200, 300, 300);
f.addWindowListener (new WindowAdapter()
{
public void windowClosing(WindowEvent e)
{
System.exit(0);
}
});
f.setVisible (true);
}
// ================================================================
// This is a Subclass of JLabel that supports drag and drop
// ================================================================
class DraggableLabel extends JLabel
implements DragSourceListener
, DragGestureListener
, DropTargetListener
{
public DraggableLabel(String s)
{
super (s);
DragSource dragSource = new DragSource();
dragSource.createDefaultDragGestureRecognizer(this
, DnDConstants.ACTION_COPY_OR_MOVE
, this);
DropTarget dropTarget = new DropTarget (this, this);
}
// This label changes the cursor when the mouse flys over it
//
public void processMouseMotionEvent(MouseEvent e)
{
// Allow Drag/Drop the first crack at mouse events
super.processMouseMotionEvent(e);
if(!e.isConsumed())
{
setCursor(Cursor.getPredefinedCursor(Cursor.HAND_CURSOR));
}
}
public void dragGestureRecognized(DragGestureEvent e)
{
StringSelection transferable = new StringSelection(getText());
e.startDrag(DragSource.DefaultCopyDrop, transferable, this);
}
public void dragDropEnd (DragSourceDropEvent e)
{
System.out.println("Label: DragDropEnd");
}
public void dragEnter (DragSourceDragEvent e){}
public void dragExit (DragSourceEvent e){}
public void dragOver (DragSourceDragEvent e){}
public void dropActionChanged (DragSourceDragEvent e){}
public void dragEnter (DropTargetDragEvent e)
{
System.out.println("Entering Drop Target");
e.acceptDrag (DnDConstants.ACTION_COPY);
}
public void dragExit (DropTargetEvent e)
{
System.out.println("Exiting Drop Target");
}
public void dragOver (DropTargetDragEvent e)
{
e.acceptDrag (DnDConstants.ACTION_COPY);
}
public void drop (DropTargetDropEvent e)
{
try {
Transferable tr = e.getTransferable();
if (tr.isDataFlavorSupported (DataFlavor.stringFlavor))
{
e.acceptDrop(e.getDropAction());
String s = (String)tr.getTransferData (DataFlavor.stringFlavor);
System.out.println("Accepting Drop of '"+s+"'");
setText(s);
e.dropComplete(true);
} else {
System.err.println ("Rejected");
e.rejectDrop();
}
} catch (IOException io) {
io.printStackTrace();
e.rejectDrop();
} catch (UnsupportedFlavorException ufe){
ufe.printStackTrace();
e.rejectDrop();
}
}
public void dropActionChanged(DropTargetDragEvent e)
{
}
}
}
/*
Here's the JDB Thread Dump at the time of deadlock
C:\Dev\com\sssw\test\Jdk12>java -version
java version "1.2"
Classic VM (build JDK-1.2-V, native threads)
C:\Dev\com\sssw\test\Jdk12>\jdk1.2\bin\jdb BugDndDeadlock
Initializing jdb...
0xae:class(BugDndDeadlock)
> run
run BugDndDeadlock
running ...
main[1] Usage: java BugDndDeadlock
This test demonstrates a deadlock problem in Java-2 Drag-Drop.
Just drag text from one label to another and a deadlock will occur.
The deadlock is caused by the Label calling setCursor in MOUSE_MOVED
and can be avoided by removing the call to setCursor.
Current thread "main" died. Execution continuing...
> Entering Drop Target
Exiting Drop Target
Accepting Drop of 'Four'
Label: DragDropEnd
Entering Drop Target
Exiting Drop Target
Entering Drop Target
Exiting Drop Target
> wherei all
AWT-EventQueue-0:
[1] sun.awt.windows.WComponentPeer.setCursor (native method), pc = -1
[2] java.awt.Component.setCursor (Component:1759), pc = 16
[3] java.awt.LightweightDispatcher.retargetMouseEvent (LightweightDispatcher:1953), pc = 156
[4] java.awt.LightweightDispatcher.trackMouseEnterExit (LightweightDispatcher:1817), pc = 117
[5] java.awt.LightweightDispatcher.processMouseEvent (LightweightDispatcher:1705), pc = 25
[6] java.awt.LightweightDispatcher.dispatchEvent (LightweightDispatcher:1645), pc = 40
[7] java.awt.Container.dispatchEventImpl (Container:1019), pc = 12
[8] java.awt.Window.dispatchEventImpl (Window:714), pc = 89
[9] java.awt.Component.dispatchEvent (Component:2289), pc = 2
[10] java.awt.EventQueue.dispatchEvent (EventQueue:258), pc = 36
[11] java.awt.EventDispatchThread.run (EventDispatchThread:68), pc = 16
SunToolkit.PostEventQueue-0:
[1] java.lang.Object.wait (native method), pc = -1
[2] java.lang.Object.wait (Object:424), pc = 2
[3] sun.awt.PostEventQueue.run (PostEventQueue:363), pc = 11
AWT-Windows:
[1] java.lang.Object.wait (native method), pc = -1
[2] java.lang.Object.wait (Object:424), pc = 2
[3] sun.awt.windows.WDropTargetContextPeer.handleMotionMessage (WDropTargetContextPeer:698), pc = 107
[4] sun.awt.windows.WToolkit.eventLoop (native method), pc = -1
[5] sun.awt.windows.WToolkit.run (WToolkit:134), pc = 26
[6] java.lang.Thread.run (Thread:479), pc = 11
Screen Updater:
[1] java.lang.Object.wait (native method), pc = -1
[2] java.lang.Object.wait (Object:424), pc = 2
[3] sun.awt.ScreenUpdater.nextEntry (ScreenUpdater:79), pc = 8
[4] sun.awt.ScreenUpdater.run (ScreenUpdater:99), pc = 6
Thread-2:
[1] sun.awt.windows.WDragSourceContextPeer.doDragDrop (native method), pc = -1
[2] sun.awt.windows.WDragSourceContextPeer$1.run (WDragSourceContextPeer$1:163
), pc = 18
>
*/