I have a piece of code that works under JDK 1.8_09a and 1.2.2_05a but
generates NullPointerException under 1.3. The code and stack trace is enclosed
for your reference.

The code basically allow users to click url links inside a displayed
html document (in a JEditorPane) and then display the linked document. The
document is always properly displayed and the NPE only happens sporadically.

I spent a lot of time searching the bug database, but can not find
something similar. I suspected that this may be caused by the non-thread-safe
aspect of swing and I inserted SwingUtilities.isEventDispatchThread() inquiries
before text.setPage(), text.setCursor(), and repaint() just to make sure they
are all running in the event dispatching thread, and they are.

HTML files are included as bug report Attachments. Thanks.

< stack trace>


Exception occurred during event dispatching:
java.lang.NullPointerException
        at
javax.swing.text.ParagraphView$Row.modelToView(ParagraphView.java:688)
        at javax.swing.text.CompositeView.modelToView(CompositeView.java:238)
        at javax.swing.text.BoxView.modelToView(BoxView.java:344)
        at javax.swing.text.CompositeView.modelToView(CompositeView.java:238)
        at javax.swing.text.BoxView.modelToView(BoxView.java:344)
        at
javax.swing.plaf.basic.BasicTextUI$RootView.modelToView(BasicTextUI.java:1245)
        at javax.swing.plaf.basic.BasicTextUI.modelToView(BasicTextUI.java:818)
        at javax.swing.text.DefaultCaret.repaintNewCaret(DefaultCaret.java:872)
        at javax.swing.text.DefaultCaret$1.run(DefaultCaret.java:851)
        at java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:154)
        at java.awt.EventQueue.dispatchEvent(EventQueue.java:331)
        at
java.awt.EventDispatchThread.pumpOneEvent(EventDispatchThread.java:103)
        at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:93)
        at java.awt.EventDispatchThread.run(EventDispatchThread.java:84)

< code snippets >

  public class FileViewer extends JDialog implements HyperlinkListener
    
    // in the constructor:
    text = new JEditorPane();
    text.setEditable(false);
    text.addHyperlinkListener(this);
    
  public void hyperlinkUpdate(HyperlinkEvent e) {
    if (e.getEventType() == HyperlinkEvent.EventType.ACTIVATED) {
      URL link = e.getURL();
      if (link == null) {
        return;
      }
      linkActivated(link);
    }
  }
  protected synchronized void linkActivated(URL u) {
    Cursor c = text.getCursor();
    Cursor waitCursor = Cursor.getPredefinedCursor(Cursor.WAIT_CURSOR);
    text.setCursor(waitCursor);
    Document doc = text.getDocument();
    try {
      text.setPage(u);
    } catch (MalformedURLException e) {
      System.out.println("FileViewer.linkActivated: Malformed URL");
      text.setDocument(doc);
      Configurator.showStatus("Malformed help URL",ProgressMonitor.ERROR);
    } catch (IOException e) {
      System.out.println("FileViewer.linkActivated: IO Exception");
      text.setDocument(doc);
      Configurator.showStatus("IO Error",ProgressMonitor.ERROR);
    } finally {
      text.setCursor(c);
      repaint();
    }
  }


elaine.hsu@East 2000-12-14