In number 2. how do you determine if the EJB already exists?
> -----Original Message-----
> From: Victor Langelo [SMTP:[EMAIL PROTECTED]]
> Sent: 08 December 2000 17:33
> To: [EMAIL PROTECTED]
> Subject: Re: Singelton Bean
>
> Let me clarify my previous statement regarding singleton entity beans.
> This is
> definitely possible to do in a spec compliant way. I was only pointing out
> that
> you probably shouldn't assume that findByPrimaryKey will behave exactly
> like other
> finder methods.
>
> I have implemented singletons using BMP. Some access the database, others
> simply
> return "static" data defined in the bean's deployment descriptor. The
> pattern is
> roughly as follows:
>
> 1. There is only one primary key value for this entity.
> 2. ejbCreate should only allow one bean instance. If it already exists,
> throw
> CreateException.
> 3. ejbFindByPrimaryKey should return the primary key only when called with
> the
> single primary key value.
> 4. Create another finder, i.e. ejbFindTheInstance(), which returns the
> single
> primary key.
> 5. Either find the bean using the findTheInstance finder or using
> findByPrimaryKey
> with the single primary key value. I put the key in the home interface to
> make
> this easy.
>
> Hope this makes sense,
>
> Victor
>
>
> David Sims wrote:
>
> > > 3, I know there were attempts to introduce a singelton bean type. Is
> it
> > > possible toimplement it myself without the support of singelton bean
> through
> > > the app server?
> >
> > As Evan and Victor recently pointed out, no, you can't without making
> > certain assumptions about your app server and machine configuration.
> >
> > cheers,
> > david
>
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