Search for "optimistic locking" on google - it sounds like the patern you're after
>From: Ted Neward <[EMAIL PROTECTED]>
>Reply-To: Ted Neward <[EMAIL PROTECTED]>
>To: [EMAIL PROTECTED]
>Subject: Re: good technique for table row locking
>Date: Wed, 9 Jan 2002 23:00:59 -0800
>
> > Has anyone else tried to do something like this? Any
> > thoughts on overcoming these issues?
> >
>Don't use EJB.
>
>Since you've already got the model in mind you're trying to do, why not just
>write the raw SQL from JDBC and be done with it?
>
>Beware, though, that this kind of stateful locking logic is really easy to
>get wrong, and leave rows locked indefinitely. What usually works better is
>to place a timestamp column on each table containing the last time this data
>was modified (and make sure each UPDATE or INSERT also puts the current time
>into the column). While the user works with the data, on each subsequent
>action, compare the locally-held timestamp with the one retrieved from the
>database on each fetch, and if they differ, somebody obviously screwed with
>the row--alert the user, decide what to do from there.
>
>Contention is the enemy of scalability. Locks introduce contention. Ergo,
>reduce locks if you want to scale.
>
>Ted Neward
>{.NET || Java} Course Author & Instructor, DevelopMentor
>(http://www.develop.com)
>http://www.javageeks.com/tneward
>
>----- Original Message -----
>From: "Michael Remijan" <[EMAIL PROTECTED]>
>To: <[EMAIL PROTECTED]>
>Sent: Saturday, January 05, 2002 7:31 AM
>Subject: [EJB-INT] good technique for table row locking
>
>
> > Hi group,
> >
> > I'd like to effectively do a "select ... for update"
> > SQL query so that other's can't mess around with those
> > rows while I have them. Although this is easy to do,
> > the problem I'm having implementing this with J2EE is
> > dealing with UserTransaction. Specifically, my
> > problems are:
> >
> > (1)
> > a UserTransaction doesn't "refresh" itself like an
> > HTTP session object does, so it always times out.
> >
> > (2)
> > There is no listener or callback method I can use for
> > user defined transactions that will alert the bean
> > when the transaction has timed out.
> >
> > (3)
> > When the transaction does time out, it's status is
> > changed to marked for rollback but doesn't actually do
> > the rollback.
> >
> > Has anyone else tried to do something like this? Any
> > thoughts on overcoming these issues?
> >
> > Thanks in advance,
> > Mike
> >
> >
> >
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>
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