"Jeffery, Myles" wrote:
> In number 2. how do you determine if the EJB already exists?
Depends on how you are storing the data. If data comes from bean's environment,
there is no need to create the entity, it always exists. I always throw an
exception in this case.
If it's stored in the database, use the same techniques you would with any other
entity bean. Generally, I use a unique primary key index which causes an sql
exception when trying to insert a duplicate.
--Victor
>
>
> > -----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
> >
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