This week's book giveaway is in the OCPJP forum. We're giving away four copies of OCA/OCP Java SE 7 Programmer I & II Study Guide and have Kathy Sierra & Bert Bates on-line! See this thread for details.
A mysql database in the background of the web server stores some information about the user.
If the user is logged into the system a userdependant page will be displayed. I store his session and username of the sql database temporary in a serialized final class object to identify the user (Session binding).
An external Java program is able to communicate through the Internet by using an XML-RPC server interface integrated in another servlet with the same serialized class and database to check if the user is online. If this is the case I want to trigger a pop up on the users computer if a special event on this java program happens. The pop up is not related to any mouse movement or button click of the user!
The pop up should only be displayed if an event on the program side happens!!
Joe, You can't send a request to the user browser without them doing something. You could have the user's browser periodically pool your server to see if it should create the pop-up, but the server can't initiate it.