AW: AW: Synchronizing ejb method

If you quote the spec you should read it very very carefully. "The =
container may throw..." is  just a recommendation for the container =
developer, not a must have. I had to experience this problem in a real =
world project, where ATG Dynamo Application Server did not throw such an =
exception on concurrent access to a stateful bean.

As I said in my first posting there should be no state in a stateless =
bean so no need to synchronize. Unless you share the client id =
explicitly you will also not get into the situation, that two different =
clients access a stateful bean at the same time.

To make further discussion easier, Ashwani, you should tell us why you =
want to synchronize (is there a state in the instance, some static =
state, DB DB state?) and on what object this snychronization should =
happen (on EJB instance, on method for all instances, or on some member =
or static object?).

Regards, Andreas.
http://www.andiberg.de/

________________________________

Von: A mailing list for Enterprise JavaBeans development =
[mailto:[email protected]] Im Auftrag von Kalra, Ashwani
Gesendet: Freitag, 19. Mai 2006 07:37
An: [email protected]
Betreff: Re: AW: Synchronizing ejb method


You are right John, It just got out of my mind that batch process is not =
a web client.
=20
Thanks
Ashwani

________________________________

From: Johan Eltes [mailto:[email protected]]=20
Sent: Friday, May 19, 2006 11:03 AM
To: Kalra, Ashwani
Cc: [email protected]
Subject: Re: AW: Synchronizing ejb method


I don't think the batch and the clients will get th same session id. =
That's the whole idea of stateful session beans - that each client gets =
its own instance and that the instance has affinity for requests from =
its owning "user" during the lifetime of the users session. I would =
recommend application-controlled database state management for locking =
out one type of client from the other (with stateless session bean).=20

/Johan

19 maj 2006 kl. 06.15 skrev Kalra, Ashwani:


        No its not correct.=20
        Section 7.5.8 , Ejb 2.1
        =20
        "Clients are not allowed to make concurrent calls to a stateful session =
object. If a client-invoked business

        method is in progress on an instance when another client-invoked call, =
from the same or different client,

        arrives at the same instance of a stateful session bean class, the =
container may throw the

        java.rmi.RemoteException to the second client[7] if the client is a =
remote client, or the

        javax.ejb.EJBException if the client is a local client. This =
restriction does not apply to a stateless

        session bean because the container routes each request to a different =
instance of the session bean

        class."

        I think there is no standard approach as Andreas said. My problem is =
that there is some batch process running and there is jsp page that can =
access the same method of ejb which I wanted to avoid. I think I can use =
statefull session bean so that at least second client gets the =
exception.

=09
        =20

        Thanks

        Ashwani

=09
        =20
=09
        =20

________________________________

        From: A mailing list for Enterprise JavaBeans development =
[mailto:[email protected]] On Behalf Of Tareq Ayub
        Sent: Friday, May 19, 2006 7:55 AM
        To: [email protected]
        Subject: Re: AW: Synchronizing ejb method
=09
=09
        Refer to the EJB spec. The container will not allow multiple threads to =
use the same instance of an SLSB. From the spec - "The container must =
ensure that only one thread can be executing an instance at any time". =
Given that, why would you want to synchronize on an EJB method anyways ? =
Also, SLSB have no state (no instance variables).  The same principle =
applies to SFSB in addition to the fact an instance is tied to a single =
client.=20

        Tareq=20
=09
=09
        On May 15, 2006, at 2:40 AM, Andreas Berg wrote:


                You shouldn't. The only reason to synchronize a stateless session bean =
is if your bean is not stateless. Then ask yourself why you chose a =
stateless bean for some stateful purpose.
                =20
                If you really want to synchronize your SLSB you need to think about =
the runtime environment. If all the instances of the SLSB run in a =
single JVM, you can use the standard Java synchronization features =
inside the bean to synchronize. But this doesn't work with a clustered =
environment. AFAIK there is no standard approach to solve this.
                =20
                Kind regards,
                =20
                Andreas.
                =20
                =20
                Andreas Berg
                Zelfi AG
                Hechtsheimer Stra=DFe 33
                55131 Mainz
                Telefon: 06131-9064850
                Telefax: 06131-9064853
                [email protected]
                http://www.zelfi.com/
                =20

________________________________

                Von: A mailing list for Enterprise JavaBeans development =
[mailto:[email protected]] Im Auftrag von Kalra, Ashwani
                Gesendet: Montag, 15. Mai 2006 06:42
                An: [email protected]
                Betreff: Synchronizing ejb method
        =09
        =09
                Hi,
                The client of my ejb can be an jsp or standalone java class.  How can =
I synchronize access to the SLSB ejb method? I am using ejb2.0 version
                =20
                =20

                __________________=20
                Regards=20
                Ashwani Kalra=20
        =09

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