The FoodSmart example application on the GemStone developer's guide CD
combines EJB with an OODBMS (i.e., GemStone). FoodSmart is architected to
be able to switch between OODBMS persistence and relational persistence
according to a property read at system startup time. It uses stateless
session beans for the service layer, and other startup properties control
whether certain domain objects are encapsulated by entity beans or not (it
has a complete domain model implemented with plain old java objects - we
created entity beans to wrap some of the domain objects, but not all). I
too am skeptical of the viability of using exclusively entity beans to model
a highly complex domain, due to inheritance and relationship limitations,
and due to scalability questions if lots of domain abstractions are modeled
with heavyweight remotable objects (i.e., entity beans). And of course I
prefer to avoid O/R mapping as much as possible ;-)
You can get the developer's guide CD (which includes an eval copy of
GemStone/J) from http://www.gemstone.com.
Randy Stafford
Senior Architect
GemStone Professional Services
> -----Original Message-----
> From: Bert Robben [SMTP:[EMAIL PROTECTED]]
> Sent: Wednesday, March 01, 2000 11:44 AM
> To: [EMAIL PROTECTED]
> Subject: Re: EJB and ODBMS
>
> > Is someone has already made a design with an appserver and a ODMS?
> > In particular, have you use
> > * Only Session bean,
> > * Some Entity bean
> > * what type of ODBMS ?
>
> Yes, we're setting up such an architecture. We want to build collaborative
> applications with complex business objects and constraints.
>
> We are planning to use no entity beans and only stateless session beans.
>
> Reasons:
> * entity beans constrain us too much (for instance w.r.t. querying, db
> clustering, indexing)
> * relationships/inheritance is too difficult with entity beans
> => we prefer to use persistent objects as domain objects
> * relative benefits w.r.t. OODB are minor (for instance no O/R mapping)
>
> And yes, we do need to write a large amount of support software on top of
> EJB before we can write applications (for instance business constraints,
> client caching, ...).
>
> I am happy to discuss this in more detail if people are interested.
>
> regards,
>
> Bert
>
> PS: For products, we're considering Weblogic + ObjectStore/Javlin
>
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