How to use singleinstance service with a JWS application

Question

Hello,
I have a Swing application and i am using Java web start to deploy on the user machines.
I want to know how to implement the single instance service. so that only one instance os the application is running.
Where should i use the singleinstance class provided by JNLP api.
for ex:
package test;
import java.awt.BorderLayout;
import javax.swing.JFrame;
import javax.swing.JOptionPane;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTextArea;
import javax.swing.border.EmptyBorder;
import java.util.Date;
// classes of the web-start API, used in this example.
import javax.jnlp.SingleInstanceListener;
import javax.jnlp.SingleInstanceService;
import javax.jnlp.ServiceManager;
import javax.jnlp.UnavailableServiceException;
/** A test of the SingleInstanceService using the web-start API.
@author Andrew Thompson
@version 2007/1/8
public class SingleInstanceApplication
extends JFrame
implements SingleInstanceListener {
/** A simple editing area. */
JTextArea document;
/** Assemble the GUI. */
SingleInstanceApplication() {
super("JNLP API single instance service");
try {
SingleInstanceService singleInstanceService =
(SingleInstanceService)ServiceManager.
lookup("javax.jnlp.SingleInstanceService");
// add the listener to this application!
singleInstanceService.addSingleInstanceListener(
(SingleInstanceListener)this );
} catch(UnavailableServiceException use) {
use.printStackTrace();
System.exit(-1);
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
document = new JTextArea(
"Try openning another version of this application\n");
document.setEditable(false);
JPanel main = new JPanel(new BorderLayout());
main.add(new JScrollPane(document));
main.setBorder( new EmptyBorder(8,8,8,8) );
getContentPane().add(main);
pack();
setSize(400,300);
setLocationRelativeTo(null);
/** Specified by the SingleInstanceListener interface
@param args The command line parameters used for this invocation */
public void newActivation(String[] args) {
StringBuffer sb = new StringBuffer();
for (int ii=0; ii<args.length; ii++) {
sb.append("'" + args[ii] + "' ");
String message = "Got new args: " + sb.toString();
// this usually serves to alert the user the app.
// wants attention. On Win. it will flash the
// apps. icon in the task bar.
JOptionPane.showMessageDialog(this, message);
// also add the new args and time to the document.
document.append( new Date() + "\t" + message + "\n" );
/** Construct the GUI and display it. If the user double clicked
a file to start the application, begin measures to load that file. */
public static void main(String[] args) {
SingleInstanceApplication app =
new SingleInstanceApplication();
app.setVisible(true);
in my progrma there are many clasess where should i use this.
Pls help new bie!!
Thanks and Regards

Answer 1

To work for your project, the SIS has to be implemented on the class that is the main(). To implement the SIS for a class, it needs to declare it implements the SingleInstanceListener and define the new activation method. Also, it needs to have the SingleInstanceService added to it via. the methods addSingleInstanceListener(). It is not strictly necessary to call addSingleInstanceListener() from the main() class, but it does make a lot of sense.
Does that answer your question?
Edited by: AndrewThompson64 on Dec 15, 2007 1:28 AM
Edited by: AndrewThompson64 on Dec 15, 2007 1:48 AM