> 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
>
>
>
> __________________________________________________
> Do You Yahoo!?
> Send FREE video emails in Yahoo! Mail!
> http://promo.yahoo.com/videomail/
>
>
===========================================================================
> To unsubscribe, send email to [EMAIL PROTECTED] and include in the
body
> of the message "signoff EJB-INTEREST". For general help, send email to
> [EMAIL PROTECTED] and include in the body of the message "help".
>
>
===========================================================================
To unsubscribe, send email to [EMAIL PROTECTED] and include in the body
of the message "signoff EJB-INTEREST". For general help, send email to
[EMAIL PROTECTED] and include in the body of the message "help".
