Sunil Kuchipudi wrote:
> Seth,
> I am not sure if you would need to enforce singleton type on design pattern
> when it comes to EJB. From what I know, the container will allocate and
> manage the pool of beans and decide on the number of beans instances
> depending on the traffic. As such, the bean developers should not have to
> worry about about concurrency control and threading issues. These issues
> should now be handled by the EJB container.
>
> Based on this premise, I do not understand why some ppl are looking to
> implement the singleton pattern. Please enlighten me if I am missing
> anything here.
Consider a situation where all beans would want to share a single
service. The singleton class lives in the same VM as the beans. If
beans are spread across VMs then there is a singleton per VM.
>
>
> Thanks.
> -Sunil .K
> ----- Original Message -----
> From: Seth Hawthorne <[EMAIL PROTECTED]>
> To: <[EMAIL PROTECTED]>
> Sent: Wednesday, May 31, 2000 12:32 AM
> Subject: Singleton design/implementation techniques
>
> > We have worked with C++ for the past 5 years, but are new to EJB
> design/implementation. One of our biggest challenges is knowing when to map
> C++ design paradigms that we are familiar with (signeltons, polymorpism,
> ...etc) to EJBs and knowing when we should be thinking in terms of different
> paradigms.
> >
> > For instance, there are a number of places in our design where we have
> "manager" objects that encapsulate a collection of objects from which they
> select an object to delegate work to. Such "manager" objects are logically
> singeltons, however, EJBs seem not to provide a direct representation for
> singeltons. This leads to a number of related questions:
> >
> > 1) Is this design approach reasonable? Are there any EJB patterns that
> might apply?
> >
> > 2) We have seen several approaches to implementing singletons mentioned in
> this newsgroup. The first is creating an object bound using JNDI, and the
> second is creating an object with a static accessor. Which approach is
> generally preferred? What are the pros and cons?
> > Does using a JNDI based object pose the risk of a single point of failure
> or scaling problems?
> >
> > 3) When should the singleton objects be created and initialized? Should
> this always be done on server startup?
> >
> > Any and all input is greatly appreciated. Thanks!
> >
> > Seth Hawthorne
> > OpenGrid
> >
> >
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