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From Juan Alvarez Ferrando <jaferra...@oviedo.syseca.es>
Subject Re: Expert advice needed
Date Tue, 09 May 2000 11:48:27 GMT
Shaun Campbell wrote:
> 
> ----------------------------------------------------------------
> BEFORE YOU POST, search the faq at <http://java.apache.org/faq/>
> WHEN YOU POST, include all relevant version numbers, log files,
> and configuration files.  Don't make us guess your problem!!!
> ----------------------------------------------------------------
> 
> First of all apologies if this is not the correct forum for asking this
> question but I have looked everywhere and cannot find the solution.
> 
> I have written a scheduling engine in Java which loads up data from a
> database using JDBC and whirrs away for anything up to half an hour
> calculating a solution, which is then posted back to the database.  I run
> this from the command line at the moment but I need to put a graphical front
> end to it:
> 
> a) set up initial parameters.
> b) provide feedback to the user on progress.
> c) provide a cancel facility to stop the scheduler.
> 
> I was thinking of converting my application to a servlet, and using an
> applet in a browser to control it, but I can't see how to get an applet to
> provide ongoing communication with a servlet.  All the examples I have seen
> show servlets basically returning HTML back to the browser as a one-off
> process.
> 

As extracted from O'Reilly's JAVA Servlet Programming (pg. 49):

Not only do servlets persist between requests, but so do any threads
created by servlets. This perhaps isn't useful for the run-of-the-mill
servlet, but opens up some interesting possibilities. Consider the
situation where one background thread performs some calculation while
other threads display the latest results. It's quite similar to an
animation applet where one thread changes the picture and another one
paints the display.

I've never tested this myself, and don't know if Tomcat conforms to it's
principle, but it may be a start point.

Juan Alvarez Ferrando


> Has anybody got any suggestions as to how I can do this sort of thing?
> 
> Thanks
> 
> Shaun Campbell
> 
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