Hi Johnny,
At 05:42 PM 4/28/2002 -0700, Johnny Ren wrote:
>Hi,
>
>I am new to Cayenne project. I will be very likely to
>join your project two weeks from now after I finish my
>SUN certified java programmer test.
Good luck with that :-).
>I do have some questions regarding the transactional
>behavior topic.
>
>1: the topic itself
> > "Transactional behavior of Cayenne when used for
> > data persistence in
> > Stateful Session Beans".
>
>Why do you only mention Stateful Session Beans ? Do
>you plan to use different strategy for Stateless
>Session Beans, Stateful Session Beans and BMP ?
>
>It seems to me that only one strategy should be used
>for those beans.
I think Cayenne is not an efficient tool to be used in Entity beans for
BMP. It would require a set of Cayenne access and map classes (DataNode,
DataMap, entities) to be created within every bean instance. Looks like
lots of overhead. Unless we find a way to make a single "Cayenne instance"
to be shared between all the entity beans, I don't think it is feasible. I
am open to suggestions though.
I was concentrating on beans that can implement SessionSynchronization
interface, since it provides hooks for Cayenne to save data or undo
changes. In fact Cayenne architecture maps rather well to that. Note that
only *stateful session* beans can implement this interface. Therefore this
specific discussion.
>2: transaction attributes
> > by the container. Furthermore there are 3 types of
> > EJB transaction
> > attributes:
>
>The attributes you mentioned are CMP attribute. They
>are not applied to Session beans and BMP.
I am no big EJB expert, but I think you are wrong on that. These attributes
are specified in deployment descriptor of any kind of bean and are applied
by bean business method.
As for my questions they were not about CMP like behavior. I don't see how
we can help with BMP of Entity beans in any reasonable way (again unless
there is a way to use shared instance of Cayenne from beans and not via a
remote call, but rather locally). I suggest to concentrate on persistence
in workflow EJBs.
As for real CMP, we are planning to use Cayenne as an O/R plugin for an EJB
server (JBoss for instance). This would be a very cool deployment scenario
and would make Cayenne a much more used tool (even though I hate EJB as
technology, a good CMP may make it bearable :-)). But this feature is not
on our immediate schedule yet (unless there is a volunteer to pick it up ;-)).
Andrus
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