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copied!<p>Okay... What you're asking is a little fuzzy so let me rephrase: </p> <ul> <li><p>You have a user (USER1) who opens a web page and sees some data.</p></li> <li><p>You have a second user (USER2) (who may be an application) who is able set a value from time to time.</p></li> <li><p>When USER2 updates that value you want USER1 to see it change in their open browser window?</p></li> </ul> <p>If this is the case you need to understand basic ajax. For that get these demo applications working: </p> <p>This example uses dojo and perhaps the S2 ajax tag lib I don't remember I prefer not to use ajax tags (as they are deprecated and prefer jquery for ajax):</p> <p><a href="http://struts.apache.org/2.x/docs/struts-2-spring-2-jpa-ajax.html" rel="nofollow">http://struts.apache.org/2.x/docs/struts-2-spring-2-jpa-ajax.html</a></p> <p>This example here shows a very similar application but using jquery, no tag library, upgraded to Spring 3, it still needs polish:</p> <p><a href="http://www.kenmcwilliams.com/Downloads/" rel="nofollow">http://www.kenmcwilliams.com/Downloads/</a></p> <p>Now that you know how to get data via ajax, look at the request with firebug. You'll see that the request is just like a typical function call, the browser keeps waiting for the data to come back.</p> <p>What you do is simply not return from the action until new data is provided. This is called <em>long polling</em> see: <a href="http://en.wikipedia.org/wiki/Comet_%28programming%29#Ajax_with_long_polling" rel="nofollow">http://en.wikipedia.org/wiki/Comet_%28programming%29#Ajax_with_long_polling</a> </p> <p>If you have not written a simple chat program, using just terminal windows I recommend you do so. Two windows per client (client-send, client-receive windows) and you'll need a server program. I remember hacking one together in a few hours using _Thinking In Java 2nd Edition (Later books took out the networking section if I remember correctly). Anyways between understanding client server interaction and long polling will let you get things working. It would be fun to extend the simple terminal based chat application to a S2 ajax chat application. Would make an awesome tutorial! PS: This is just an application of the producer/consumer problem (If you understand that then I guess you don't need to do the fun exercise).</p> <p>The interfaces would look very pretty if the server was managed by spring. I know there must be nice servers already written but I am not familiar with any, but would love to hear of one.</p>

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