Multithreaded GUI creation

Question

Hi,
I'm working on a project that uses EJB's for business work and Swing for the GUI.
The major problem is that the EJB's calls can be quite long to return.
As I am populating combos and tables from the results of these calls, it is problematic since it slows down the bring up of the GUI.
I have implemented a threaded model of the component loading.
I'd like to have your advise on this, if it's good or not and if there are possible improvements.
Here are the two classes I have build from now :
- this is the initComponents() part of the main class. It creats a PersonneChooser and waits until it has finished to load (in order to avoid NullPointerException due to calls to the paint() method of the main frame)
  private void initComponents() {
    try     {
      java.util.logging.Logger.getLogger("root").info("Creating PersonneChooser");
      PersonneChooser pc = new PersonneChooser();
      java.util.logging.Logger.getLogger("root").info("Done");
      pc.addActionListener(this);
      pc.getThread().join();
      this.getContentPane().add(pc);
      this.pack();
      this.setVisible(true);
    catch(SecurityException e) {
        System.out.println("Op not allowed");
  }- this is the PersonneChooser. It is a combo box populated with the objects returned from a call to an EJB method. It has an embeded renderer for the viewing.
public
  class PersonneChooser
  extends javax.swing.JComboBox
  implements Runnable {
    private Thread _thread = null;
    public Thread getThread() {
      return _thread;
    public void run() {
      java.util.logging.Logger.getLogger("root").config("Assigning PersonneChooserRenderer");
      setRenderer(new PersonneChooserRenderer());
      java.util.logging.Logger.getLogger("root").config("Populating combo");
      try {
     Iterator i = HomeCaching.getInstance().getCalendrier().getAllPersonnes().iterator();
     while(i.hasNext()) {
       addItem(i.next());
      java.util.logging.Logger.getLogger("root").config("Done");
      catch(Exception e) {
     e.printStackTrace();
    public PersonneChooser() {
      _thread = new Thread(this);
      _thread.start();
class PersonneChooserRenderer
  extends javax.swing.JLabel
  implements javax.swing.ListCellRenderer {
    public PersonneChooserRenderer() {
      setOpaque(true);
      setHorizontalAlignment(javax.swing.SwingConstants.CENTER);
      setVerticalAlignment(javax.swing.SwingConstants.CENTER);
    public java.awt.Component getListCellRendererComponent(
      javax.swing.JList list,
      Object value,
      int index,
      boolean isSelected,
      boolean cellHasFocus) {
      if (isSelected) {
     setBackground(list.getSelectionBackground());
     setForeground(list.getSelectionForeground());
      else {
     setBackground(list.getBackground());
     setForeground(list.getForeground());
      PersonneValue pv = (PersonneValue)value;
      setText(pv.getNom() + " " + pv.getPrenom());
      return this;
}thanks,
ionel

Answer 1

Hi,
thanks for your reply.
I have changed my code to
      java.util.logging.Logger.getLogger("root").info("Creating PersonneChooser");
      PersonneChooser pc = new PersonneChooser();
      java.util.logging.Logger.getLogger("root").info("Done");
      pc.addActionListener(this);
      this.getContentPane().add(pc);
      this.pack();
      this.setVisible(true);for the initComponents() part
and
      java.util.logging.Logger.getLogger("root").config("Setting up self Action listening");
      addActionListener(this);
      java.util.logging.Logger.getLogger("root").config("Assigning PersonneChooserRenderer");
      setRenderer(new PersonneChooserRenderer());
      disable();But when I launch the app, i get an NPE
     [java] java.lang.NullPointerException
     [java]     at org.TechAdvantage.intranet.client.gui.PersonneChooserRenderer.getListCellRendererComponent(Unknown Source)
     [java]     at javax.swing.plaf.metal.MetalComboBoxButton.paintComponent(MetalComboBoxButton.java:143)
     [java]     at javax.swing.JComponent.paint(JComponent.java:804)
...I didn't understand what did you mean by "disable JComboBox in the event dispatch thread). Does the disable() method do this ? If so, why do I get the NPE ?
thanks,
ionel