Laurel:
I think Anish meant to say that when using SELECT FOR
UPDATE, unless a commit, rollback, or a deadlock
exception occurs the DB will block other statements..
<guessing>
If you were to use CMT, won't an attribute of
RequiresNew for the checkValue() method, ensure that
when the call returns, the lock will be released ?
</guessing>
thanks/.
- arun
--- Laurel Neustadter <[EMAIL PROTECTED]>
wrote:
> Hi Anish:
>
> I don't understand your answer. In the app servers I
> have worked with, if
> you are using a DataSource, autocommit is always
> turned off. If
> container-managed transactions are not being used,
> the transaction is
> demarcated via UserTransaction::begin() and
>
UserTransaction::commit()/UserTransaction::rollback(),
> even if an update is
> performed.
>
> Do you advocate by-passing the
> DataSource/UserTransaction classes? If so,
> what is your reasoning? (e.g., performance?)
>
> Thanks.
>
> Laurel
>
> -----Original Message-----
> From: Anish Malhotra [mailto:[EMAIL PROTECTED]]
> Sent: Friday, August 31, 2001 9:05 AM
> To: [EMAIL PROTECTED]
> Subject: Re: critical sections in beans
> (transactions?)
>
>
> If you do not do an update, you need to point to the
> container that the
> transaction is over, either by manually saying it or
> by throwing a remote
> exception in case of one.
>
> Anish
>
> -----Original Message-----
> From: Bill Leonard [mailto:[EMAIL PROTECTED]]
> Sent: Wednesday, August 29, 2001 11:30 AM
> To: [EMAIL PROTECTED]
> Subject: Re: critical sections in beans
> (transactions?)
>
> Thanks, Laurel, for looking at this.
>
> I put the checkValue() function as part of the
> transaction. My question: if
> I don't subsequently perform an update on the data,
> I assume EJB will tell
> the resource manager to release the lock?
>
> THanks,
> Bill
>
> -----Original Message-----
> From: Laurel Neustadter
> [mailto:[EMAIL PROTECTED]]
> Sent: Wednesday, August 29, 2001 9:38 AM
> To: 'Bill Leonard'; [EMAIL PROTECTED]
> Subject: RE: critical sections in beans
> (transactions?)
>
>
> Hi Bill:
>
> Is myEntityBean.checkValue() checking the value of a
> persistent field? If
> so, why can't that call be part of your transaction
> ... i.e.,
>
> // start transaction
> if (myEntityBean.checkValue())
> {
> myOtherEntityBean.update();
> myEntityBean.update();
> // end transaction
> }
> // end critical section
>
>
> If you need a write lock on the value you are
> checking, you probably need to
> use BMP so you can do a SELECT ... FOR UPDATE. You
> probably want an
> isolation level of Serializable.
>
> Is there a reason why making
> myEntityBean.checkValue()part of the
> transaction is unworkable? Some more background on
> what you are trying to
> accomplish with myEntityBean.checkValue()would be
> helpful ...
>
> Laurel
>
> -----Original Message-----
> From: Bill Leonard [mailto:[EMAIL PROTECTED]]
> Sent: Wednesday, August 29, 2001 6:20 AM
> To: [EMAIL PROTECTED]
> Subject: critical sections in beans (transactions?)
>
>
> I have the following SessionBean method and want to
> block other clients when
> they try to call checkValue() if another client is
> already in the critical
> section. Further, I need to execute an update to
> the enity bean and another
> entity bean in a transaction.
>
> Can I do this using transactions and isolation
> levels in EJB?
>
> MySessionBean
> {
> mySessionBeanMethod()
> {
> // start crtical section
> if (myEntityBean.checkValue())
> {
> // start transaction
> myOtherEntityBean.update();
> myEntityBean.update();
> // end transaction
> }
> // end critical section
> }
> }
>
> Thanks,
> Bill
>
>
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