Java EE (Java Enterprise Edition) General Discussion

Hi !

I'm sorry if I'm posting it in the wrong section, but I really did not find anything better ... after all my post is about servet too, even though the problem is not with the servlet :)

I have been reading a lot of stuff lately on the subject of "Reverse AJAX". By some coincidence, the first real webapp which I want to make relies on server pushes, that is, the data on the server constantly changes and I want to be able to update the client's browsers with latest info from the server.

Now what I found out is that I need "active" server-push, to be even more preceise, I'm looking for an implementation of the Comet technique and not Polling or Piggyback, though I guess polling would do the trick, but then again, I can do this very well without server-pushes - AJAX + polling = emulation of server pushes, but I don't want that, which is why I want to implement the Comet technique.

The problem:

There are very few articles which describe what I need, and some of those which are relatively good have sample code which doesn't work for me. Moreover, some samples are too simple and I wouldn't know how to apply that code in my situation.

My problem:

1) My webapp in itself is a servlet with a running thread which polls several other (for instance X) servers;
2) For each of the X servers it creates an object which contains the state of those servers. The state of the servers often changes. Each such instance of a data object is about 1200 bytes.
3) I have Y number of clients which should connect to my servlet and without refreshing the page must get up to date information about each of the X servers.
4) The information about the state of each of the X servers is displayed as a row in an HTML table.
5) So that means that even the number of rows in the table may vary - be dynamic - for example, when one of the X servers goes down, or up.
6) ideally, my servlet would pass/push the Data[] array with info about each server to all monitoring browsers, and the client side HTML/javascript/whatever would re-render the HTML page using DOM or something.

Thing is I know what want, but I am not sure which of the available Comet implementations will do better what I need. The best example of what I need I found here:

http://upl.codeq.info/ajaxkurs/stocks.html

(roll over the table to initialize stocks)

This example is alsmost a perfect example of what I need, the only thing it does not do is that it does not change the number of rows. But I'm sure this can be done as this example does it:
http://upl.codeq.info/ajaxkurs/persontable.html

and all of this is implemented using DWR. Needless to say, all the sample code does not work for me and I don't know why. I've added some comments here:
http://today.java.net/pub/a/today/2007/03/22/developing-applications-using-reverse-ajax.html

Some ideas? Advice? Architectural advice? I'm mainly worried about how would I send the array of data objects ... should I send the objects or should I generate the new table on the server side and push it as javascript ... I'm a bit lost honestly.

I would really appreciate some help,
Regards,
Oleg