Write a thread to check database in web application 2007-11-05 - By Ashish Kulkarni
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Hi
I dont need more then one thread, or a timer job i would say, this timer
should sleep and then activate like after 10 minutes, check the database, if
there is nothing to do go back to sleep.
I will look into quartz, is it ok to use Java Timer and TimerTask to do it.
For example this will be my taslk
class MyTimerTask extends TimerTask
{
public void run()
{
//Class to check for database
}
}
Timer tt = new Timer();
tt.scheduleAtFixedRate(myTimerTask, 100000, 100000);
In ServletContext i will save instance of myTimerTask and then provide a jsp
to stop or start this Task
I will make sure that the class with does check database function will not
go in loop or be there for ever
Any suggestions
On 11/5/07, Frank W. Zammetti <fzlists@(protected)> wrote:
>
> 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)
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>
>
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