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Struts & Hibernate
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| | | concurrency problem | concurrency problem 2005-04-08 - By Kalra, Ashwani
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That is not the scenario. here two actions are calling the same stateful
session bean's method. when user quickly invokes some other action, while
previous one is still executing. Both action classes/instances are different
Thanks & Regds
Ashwani
Ext: 1860
> -- --Original Message-- --
> From: An interest list for Sun Java Center J2EE Pattern Catalog
> [mailto:J2EEPATTERNS-INTEREST@(protected)]On Behalf Of Vijay K Dasari
> Sent: Friday, April 08, 2005 7:02 PM
> To: J2EEPATTERNS-INTEREST@(protected)
> Subject: Re: concurrency problem
>
>
> Hi,
>
> If you are using STRUTS and you want to prevent the user from
> submitting the
> same page twice(by immediate clicks) we can use Tokens from
> STRUTS, so that
> we make only first click valid.
>
> Action class has - saveToken() and isTokenValid() methods.
>
>
> Vijay.
>
> > -- --Original Message-- --
> > From: An interest list for Sun Java Center J2EE Pattern Catalog
> > [mailto:J2EEPATTERNS-INTEREST@(protected)]On Behalf Of
> Deepak Nagaraj
> > Sent: Friday, April 08, 2005 8:19 AM
> > To: J2EEPATTERNS-INTEREST@(protected)
> > Subject: Re: concurrency problem
> >
> >
> > Hi Ashwani,
> >
> > I totally agree with what abhijit has mentioned. Application server
> > serializes the calls to the Session beans.
> >
> > It would be ideal case to handle the multiple clicks or simultaneous
> > clicks in the Action classes. If you are using struts framework, a
> > feature is already provided to handle it.
> >
> > With Regards,
> > Deepak Nagaraj
> >
> >
> > -- --Original Message-- --
> > From: An interest list for Sun Java Center J2EE Pattern Catalog
> > [mailto:J2EEPATTERNS-INTEREST@(protected)] On Behalf Of
> abhijeet rai
> > Sent: Friday, April 08, 2005 5:34 PM
> > To: J2EEPATTERNS-INTEREST@(protected)
> > Subject: Re: concurrency problem
> >
> > Hi Ashwani,
> >
> > please read below from the EJB spec 2.0 which is old
> > spec version --
> >
> > ===========> > EJB 2.0 spec
> > ===========> > "[6.5.6] Serializing session bean methods
> > A container serializes calls to each session bean
> > instance.Most containers will support many instances
> > of a session bean executing concurrently; however,
> > each instance sees only a serialized sequence of
> > method calls. Therefore a session bean does not have
> > to be coded as reentrant.
> >
> > The container must serialize all the container-invoked
> > callbacks (ejbPassivate, beforeCompletion, ...)
> >
> > Clients are not allowed to make concurrent calls to a
> > SFSB(Stateful Session Bean).The container must throw a
> > java.rmi.Exception to the second client.This
> > restriction does not apply to SLSB(Stateless Session
> > Bean)."
> >
> > Please check EJB spec 2.1 if you are using it and
> > confirm whether this is still valid.
> >
> > Hope this helps.
> >
> > Cheers
> > Abhijeet
> > BEA Support Engineer
> >
> > --- "Kalra, Ashwani" <ashwani.kalra@(protected)>
> > wrote:
> > >
> > > I am facing concurrency problem in following
> > > scenario.
> > >
> > >
> > >
> > > All our action classes call same stateful session
> > > bean . Each action class obtains the reference from
> > > HTTPSession object and calls one and only one
> > > business method.
> > >
> > > To prevent the concurrent access to this instance
> > > which occurs when user immediately presses two links
> > > quickly in succession I am using the following code
> > > block
> > >
> > >
> > >
> > > execute(...) //execute methods of Action class
> > >
> > > {
> > >
> > > .....
> > >
> > > .....
> > >
> > > //Obtain the session from Request.User will always
> > > be in session here
> > >
> > > session=request.getSession()
> > >
> > > Synchronised(session)
> > >
> > > {
> > >
> > > //call ejb's business method.
> > >
> > > }
> > >
> > >
> > >
> > > }
> > >
> > > However sometimes more than one thread is able to
> > > pass through, And I get exception from Appserver. As
> > > 2 threads are not allowed for statefull Session
> > > bean.
> > >
> > > Can there be problem in above code. Is it ok to
> > > synchronise on session object.
> > >
> > > Thanks & Regds
> > > Ashwani
> > >
> > > Ext: 1860
> > >
> > >
> > >
> > >
> > >
> > >
> > >
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