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Refreshing JSP codes to check for data updates without refreshing the entire browser(eg. does not affect a user reading a article while constantly refreshing in the backgrd)

Posted on 2003-11-13
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Last Modified: 2010-04-06
Hi.. I have a urgent question. Basically I have this site written in JSP that allows one computer to send a "instant message" to another computer(both at a specific webpage of my site). The message sent is first stored in a vector/file/db and then retrieved when computer B(reciever) refreshes the page and the codes check that boolean newMsg=true; and displays the message in a Alert box.

My problem is, the reciever has to manually click refresh to check for any new messages. What I need is for the "refresh" to somehow.. run (in the background?) without disturbing the reciever(perhaps reading a article). And when a new message is detected, the Alert box will pop up.

Hope I make this clear enough. Please help! Thanks!
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Question by:lewin85_sg
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linc0ln earned 1500 total points
ID: 9741057
I'm not sure if you can handle that completely on the server side.  I believe what you want to do is create a hidden frame or possibly an iframe, I'll call it the lookup frame.  

In the lookup frame you would run a separate jsp that does the db lookup and if new messages are found, communicates the results to the viewing frame via javascript.  The lookup frame could use a meta-refresh to periodically reload to check for new messages.

Hope this helps.

Linc
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by:jimmack
ID: 9743432
linc0ln is correct, you can't "push" from a server to a browser.  The browser is in control of the communications and the server simply responds.

<META HTTP-EQUIV=Refresh CONTENT="10; URL=http://url.to.servlet">

The meta-refresh should be nice and easy to implement (not all browsers support it, but I don't know which ones).  You could do it with an applet, but that's considerably more work ;-)
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by:Zontar
ID: 9745907
I dont'think there are any graphical browsers that produced in the last 6-7 years that don't support meta refresh tags. That shouldn't be an issue.
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by:jimmack
ID: 9746535
;-)  Thanx Zontar.
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by:lewin85_sg
ID: 9747070
Thanks guys :)
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