Re: critical sections in beans (transactions?)

[Bill Leonard]

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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