Exceptions with JEditorPane setPage() method (Catching not possible)

Question

hi all
if anyone can help me...please help
I got serious exceptions with the JEditorPane()'s setPage() method
I have written the try & catch still i could not catch the exception..(those exceptions are not displaying any of my program lines)..setPage() mehod was executed properly and the page was displyed on the editorpane..and then exceptions r coming..
--------my code--------
java.net.URL fileurl =LongTask.class.getResource(modifiedfilename);
editorpane.setPage(fileurl);
---------------------exceptions
java.lang.NullPointerException
at java.util.Hashtable.put(Hashtable.java:393)
at javax.swing.text.SimpleAttributeSet.addAttribute(SimpleAttributeSet.java:176)
at javax.swing.text.html.CSS.translateHTMLToCSS(CSS.java:687)
at javax.swing.text.html.StyleSheet.translateHTMLToCSS(StyleSheet.java:491)
at javax.swing.text.html.StyleSheet$ViewAttributeSet.<init>(StyleSheet.java:2476)
at javax.swing.text.html.StyleSheet.getViewAttributes(StyleSheet.java:312)
at javax.swing.text.html.BlockView.getAttributes(BlockView.java:275)
at javax.swing.text.html.StyleSheet$ViewAttributeSet.getResolveParent(StyleSheet.java:2609)
at javax.swing.text.html.StyleSheet$ViewAttributeSet.doGetAttribute(StyleSheet.java:2589)
at javax.swing.text.html.StyleSheet$ViewAttributeSet.getAttribute(StyleSheet.java:2569)
at javax.swing.text.ParagraphView.setPropertiesFromAttributes(ParagraphView.java:105)
at javax.swing.text.html.ParagraphView.setPropertiesFromAttributes(ParagraphView.java:87)
at javax.swing.text.html.ParagraphView.setParent(ParagraphView.java:60)
at javax.swing.text.CompositeView.replace(CompositeView.java:200)
at javax.swing.text.BoxView.replace(BoxView.java:164)
at javax.swing.text.CompositeView.loadChildren(CompositeView.java:97)
at javax.swing.text.CompositeView.setParent(CompositeView.java:122)
at javax.swing.text.html.BlockView.setParent(BlockView.java:55)
at javax.swing.text.CompositeView.replace(CompositeView.java:200)
at javax.swing.text.BoxView.replace(BoxView.java:164)
at javax.swing.text.html.TableView$RowView.replace(TableView.java:1414)
at javax.swing.text.CompositeView.loadChildren(CompositeView.java:97)
at javax.swing.text.CompositeView.setParent(CompositeView.java:122)
at javax.swing.text.CompositeView.replace(CompositeView.java:200)
at javax.swing.text.BoxView.replace(BoxView.java:164)
at javax.swing.text.html.TableView.replace(TableView.java:864)
at javax.swing.text.CompositeView.loadChildren(CompositeView.java:97)
at javax.swing.text.CompositeView.setParent(CompositeView.java:122)
at javax.swing.text.html.TableView.setParent(TableView.java:768)
at javax.swing.text.CompositeView.replace(CompositeView.java:200)
at javax.swing.text.BoxView.replace(BoxView.java:164)
at javax.swing.text.View.updateChildren(View.java:1126)
at javax.swing.text.View.insertUpdate(View.java:710)
at javax.swing.text.View.forwardUpdateToView(View.java:1217)
at javax.swing.text.View.forwardUpdate(View.java:1192)
at javax.swing.text.BoxView.forwardUpdate(BoxView.java:222)
at javax.swing.text.View.insertUpdate(View.java:716)
at javax.swing.plaf.basic.BasicTextUI$RootView.insertUpdate(BasicTextUI.java:1487)
at javax.swing.plaf.basic.BasicTextUI$UpdateHandler.insertUpdate(BasicTextUI.java:1726)
at javax.swing.text.AbstractDocument.fireInsertUpdate(AbstractDocument.java:184)
at javax.swing.text.DefaultStyledDocument.insert(DefaultStyledDocument.java:201)
at javax.swing.text.html.HTMLDocument.insert(HTMLDocument.java:232)
at javax.swing.text.html.HTMLDocument$HTMLReader.flushBuffer(HTMLDocument.java:3254)
at javax.swing.text.html.HTMLDocument$HTMLReader.addContent(HTMLDocument.java:3196)
at javax.swing.text.html.HTMLDocument$HTMLReader.blockClose(HTMLDocument.java:3128)
at javax.swing.text.html.HTMLDocument$HTMLReader$BlockAction.end(HTMLDocument.java:2334)
at javax.swing.text.html.HTMLDocument$HTMLReader.handleEndTag(HTMLDocument.java:2233)
at javax.swing.text.html.parser.DocumentParser.handleEndTag(DocumentParser.java:217)
at javax.swing.text.html.parser.Parser.parse(Parser.java:2072)
at javax.swing.text.html.parser.DocumentParser.parse(DocumentParser.java:106)
at javax.swing.text.html.parser.ParserDelegator.parse(ParserDelegator.java:78)
at javax.swing.text.html.HTMLEditorKit.read(HTMLEditorKit.java:230)
at javax.swing.JEditorPane.read(JEditorPane.java:504)
at javax.swing.JEditorPane$PageLoader.run(JEditorPane.java:551)
please share ideas to solve this problem

Answer 1

But how can I cause GUI thread to run in my thread
group? As I suppose GUI thread is started by JVM and
is something separate from my code - I can get a
reference to GUI thread but don't know how to
manipulate or replace it...One alternative is to completely separate the GUI code from your code.
Your code, which is wrapped in appropriate try/catch blocks, runs on its own thread and does its own processing. When it's done with that processing, it queues the results on the event thread for display. If an exception occurs during your processing, then you queue something that notifies the GUI.
The simplest way to implement this is to spawn a new thread for each operation. The Runnable that you give to that thread looks like the following:
public MyOperationClass implements Runnable
    public void run()
        try
            // do your exception-generating code here
            SwingUtilities.invokeLater( new MyGUIUpdateClass(param1, param2));
        catch (Exception e)
            SwingUtilities.invokeLater(new MyExceptionReporter(e));
}This is only a bare-bones solution (and hasn't been compiled). Since it separates the GUI from actual processing, you'll probably want to display a wait cursor while the processing thread is doing its thing. You'll probably end up implementing a class that implements this pattern. You may also want to create a producer-consumer thread, so that the user won't invoke, say, a dozen different operations at once.
However, this sort of code is absolutely essential to Swing programming. Most apps do extensive non-GUI processing, such as database queries. If you run such queries in the GUI thread, your GUI will freeze.
Sun has named this pattern "SwingWorker", although I don't think they've fleshed it out very fully: http://java.sun.com/products/jfc/tsc/articles/threads/threads2.html