Actually this issue has been clarified by Sun on this mailing list some
time ago.
With regards to stateless session beans, concurrent method calls are
allowed, the EJB container will delegate them to different bean
instances (the second part is well specified).
With regards to stateful session beans, concurrent method calls will
throw an exception.
Synchronization refers to the EJB container itself making calls on the
bean, these calls must be synchronized and will occur while no client is
able to make calls on that bean.
arkin
dan benanav wrote:
>
>
>
> Jose Gonzalez wrote:
>
> >
> > The EJB specification states that a single instance of an EJB
> > cannot
> > receive concurrent calls, and that the container must serialize
> > calls,
> > but I understand that this is the desired behaviour in case of a
> > program
> > invoking methods on an stateful session bean, not in the case of
> > invoking methods on stateless session beans...
> >
> > Am I right? Is NetDynamics doing right according to the EJB
> > specs?
> > If yes... how could I achieve concurrency on calls on an stateless
> > session bean?
>
> Actually the container is not responsible for serializaing calls to a
> stateful session bean in the way you think. For example suppose
> threadA and threadB are running concurrently and each thread makes the
> following invocation.
>
> myStatelessSesssion.foo();
>
> So each thread is making a call on the same method and the same entity
> object. In that case the container should (according to the spec)
> throw a RemoteException.
>
> So you may be wondering what is the meaning of the phrase,
> "A container must serialize calls to the session bean". The spec is
> talking about calls that the container makes to the session bean
> instance not calls made to the session object. Note that the
> container will make calls like ejbLoad, ejbActivate, and ejbPassivate
> in addition to calls to the business methods.
>
> To answer your question, which actually applies to both stateful and
> stateless session beans, EJB does not provide a way to serialize
> calls. To me this is a major weakness of EJB.
>
> dan
>
>
>
> >
> >
> > Greetings
> > Jose
> >
> > ========
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--
----------------------------------------------------------------------
Assaf Arkin www.exoffice.com
CTO, Exoffice Technologies, Inc. www.exolab.org
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