NotSerializableException for ToolkitImage when serializing a model in Swing - exception

Question

I have Swing application which manipulate shapes. In my toolbar I have a zoom function that the user activate by clicking on a button, then the cursor of the mouse changes to a magnifier which is an image.
My problem is actually the cursor, for some raisons, when I set the cursor on the panel displaying the shapes, I can't save my model and I get the java.io.NotSerializableException: sun.awt.image.ToolkitImage exception.
My model
public class Document implements IDocObservable,Serializable{
...
public void updateCursor() {
Iterator<IDocObserver> iter = docObservers.iterator();
while (iter.hasNext()) {
iter.next().docCursorChanged();
}
}
...
}
The action
public class ZoomInAction extends AbstractAction {
public void actionPerformed(ActionEvent arg0) {
...
Application.getInstance().getActiveDocument().updateCursor();
}
}
The display Panel (note : if I comment the setCursor(..) line, I'am able to save )
public class Window extends JPanel implements IDocObserver{
...
public void paint(Graphics g){
//drawing the differents shapes
}
#Override
public void docCursorChanged() {
setCursor(Utile.getZoomInCursor();
}
}
}
The class that provide the cursor
public class Utile {
private static Image zoomIn = toolkit.getImage(Utile.class.getResource("/images/zoomin_mouse.png"));
...
public static Cursor getZoomInCursor() {
return toolkit.createCustomCursor(zoomIn, hotSpot, "");
}
}
The writing of the object is a standard Java methode with outStream.writeObject(doc);
thanks

Answer 1

You aren't just serializing a model, you are serializing a list of IDocObservers, which includes Window extends JPanel implements IDocObserver. IOW you are serializing a JPanel. Don't do that: see the warning at the top of the Javadoc. You don't need to save the observers along with the observable, surely: can't you make that list transient?