Write a thread to check database in web application 2007-11-05 - By Frank W. Zammetti
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On Mon, November 5, 2007 10:40 am, Ashish Kulkarni wrote:
> Hi
> I have to write a thread in web application which will check some values
> in
> database, and then perform some function depending on the values.
>
> There wont be any user input and this thread should be called after like
> 10
> minutes, also i want to have a jsp page from where i can maintain this
> thread, like stop, change the time it should run etc.
>
> Are there any specific J2EE api i can use, or should i just use a time
> thread, and store the handle to this thread in servlet context so i can
> access and modify it..
Spawning threads in a servlet container is generally considered Bad
Voodoo(tm). If memory serves, it's even outlawed by the servlet spec.
That being said, we've all done it, we'll all probably do it again, so
mheh with the recommendations :)
*That* being said, the key thing is to be extra careful doing it. Make
sure the thread code is as bullet-proof as possible, most especially when
it comes to resource usage. The reason spawning such threads is a bad
idea in the first place is because they are not under control of the
container and cannot be managed, nor can the resources it uses.
Therefore, you'll need to do that yourself and be sure you play nice
within the container.
Also, be sure to mark it a daemon thread, otherwise you'll find it can and
will hold up shutdown of the container. Bumping its priority as low as
possible is probably also a good idea.
Or you can do as Chris said and use Quartz, which will deal with most of
these concerns for you. I say most because you can still write bad Quartz
jobs that bork things as badly as if you didn't use Quartz at all, but
it'll help a little bit.
> Ashish
Frank
--
Frank W. Zammetti
Founder and Chief Software Architect
Omnytex Technologies
http://www.omnytex.com
AIM/Yahoo: fzammetti
MSN: fzammetti@(protected)
Author of "Practical Ajax Projects With Java Technology"
(2006, Apress, ISBN 1-59059-695-1)
and "JavaScript, DOM Scripting and Ajax Projects"
(2007, Apress, ISBN 1-59059-816-4)
Java Web Parts - http://javawebparts.sourceforge.net
Supplying the wheel, so you don't have to reinvent it!
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