Kevin Lewis wrote:
>
> > http://www.middleware-company.com/RogerEdDebate.htm
> >
> > I'd love to hear comments and opinions.
>
> That was pretty interesting. I noticed:
>
> ...
>
> o R. Sessions didn't seem to have a grasp on the "spec" differences between
> entity and session beans (e.g., ejbStore). Was this only my interpretation?
> This also seems to come through from the things in his ObjectWatch letter.
If you try to implement "Session Beans with Automatic Failover", you will
discover that you can view session beans as entity beans with no client-visible
primary key. The fact that a session bean does not have ejbLoad/ejbStore does
not mean that the container will not use similar operations on the wrapper
object (or generated class) that it uses for ejbPassivate and ejbActivate.
It is possible to do the passivation/activation of a session bean in
ejbPassivate/ejbActivate instead of ejbStore/ejbLoad because it is assumed
that only one server at a time will be servicing that object. But in the case
of supporting automatic failover, multiple servers can end up trying to service
the same session 'object' at the same time. That requires a modification to the
way passivation and activation is handled (although this can be made mostly
transparent to the bean developer).
> o R. Sessions asserted several times that one must have a transaction to
> reference an entity bean. This is not true. Did I misinterpret what he was
> saying?
At a minimum, you need to call a finder method before you can do any useful
work with an existing entity. Perhaps this is what Roger is referring to.
> o I am more confused than ever about the stateful session equivalent in MTS.
> Would someone like to compare and contrast the two models?
As I understand it, and as we implement it, an MTS-style component that retains
conversational state can only retain it until the transaction ends, at which
time the servicing instance is destroyed or pooled.
> Good stuff, though.
>
> -Kevin
>
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