Reverse Ajax + JSP-Servlet

Question

We are trying to create a reverse ajax in our project.

I've checked on the net and didn't find something concrete. I was unable to run any of the tutorials provided successfully.

My object is: to provide on-screen alerts (like a pop-up) when ever there is an even pushed from the server (it could be high cpu usage/ram, anything).

Answer 1

The HTTP protocol (fortunately, after all) doesn't support PUSH, so it stops there.

Best what you can do is to let the client fire ajax poll requests at timed intervals I can recommend jQuery.ajax() in combination with setInterval() for this.

Alternatively (and with a bit more effort) you could make use of Comet technique (which simulates the fictive HTTP PUSH less or more). Check the appserver specific documentation/wiki using this keyword for details. Here's a Tomcat targeted example: http://wiki.apache.org/tomcat/WhatIsComet

Edit: as requested, here's a Tomcat+Comet tutorial to get started: http://www.ibm.com/developerworks/web/library/wa-cometjava/#N100CC Hope this helps.

Answer 2

Here is a valuable resource