The EJB 2.x model is being completely overhauled for the EJB 3.0 release which will be included in J2EE 5.
The main changes are that the EJB 2.x Entity Bean model has been completely dropped in favour of a lightweight persistence model which is 95% the same as the JDO 2.0 standard. So you're best bet for new applications is to develop with Session Beans + JDO persistent objects, and this will allow for easy migration to EJB 3 Entity Beans when they're delivered by some major vendors.
WebSphere 5.1 will happily run JDO - I've used Versant's VOA as well as JPOX on WAS 5.1 and WAS 6, and they run like a charm. But since WAS 6 supports J2EE 1.4 and J2EE 5 likely won't be delivered before WebSphere 7, then we'll probably have to wait until WebSphere v8 before we get an IBM release of EJB 3.
The good news for JDO adopters though, is that the major JDO vendors will be implementing EJB 3 on top of JDO 2, so you'll be able to use a pluggable EJB 3 persistence implementation into appservers like WebSphere and WebLogic, well before IBM or BEA deliver theirs. So if you go JDO now, you'll be able to stick with the same JDO vendor for EJB 3, and easily mix and match the use of the 2 APIs (i.e. use the JDO 2 API now, and then use the EJB 3 API when it's delievered on top of the same persistence runtime implementation).
Versant's Open Access product will let you do all of this, and some of the other JDO vendors have similar plans.
Dave Clark<br />Senior WebSphere Architect<br /><a href="http://www.versant.com" target="_blank" rel="nofollow">Versant Open Access - JDO2 & EJB3</a>
Joined: Jun 25, 2004
Thanks for all the great info. When is v3 set for general release?
Joined: Feb 16, 2005
the current release of Versant's Open Access for JDO implements a lot of the JDO 2.0 spec features, but since the standard was only approved a couple of weeks ago, they're busy right now making VOA fully-compliant with JDO 2.0. So the fully JDO 2.0 compliant version should be released soon-ish.
As for an implementation of VOA that implements the early draft of the EJB 3 persistence APIs - that will be Job #1 once the fully JDO 2.0 compliant release is published.
If you ask email@example.com, I'm sure they'll be able to give you more specific dates than 'soon-ish' and 'sometime after that' ;-)