Considering recent postings, I must ask the question:
"Is there any real advantage to wrap entity beans with session beans?"
Here are the reasons for my question:
- some posters have questioned the validity of encapsulating conceptually
related data inside two or more beans. I strongly agree with them.
- some posters have questioned the much publicized performance gains when
calling session beans as opposed to entity beans. I strongly agree with
them; a remote call is a remote call.
- some posters have questioned the "special capabilities" attributed to
session beans (as opposed to entity beans) "when it comes to accessing ejb's
of any type", returning custom data or dealing with transactions. I strongly
agree with them.
- some posters have complained about having to wrap all client calls to
session objects in try/catch blocks to deal with session object expirations
thus making client logic convoluted and client code brittle. See my previous
posting.
- some posters have complained that ad-hoc data already resident on the
server cannot be cached and shared among different clients. We avoid using
session beans for sharable or not client related data.
- I stated that session beans are conceptually more expensive on the server
than entity beans (the server has to manage timeouts).
- I raised the issue that some platforms cannot conceptually reclaim
unreferenced entity objects thus leading to resource exhaustion.
I certainly hope, based on the above, that some posters of this list are not
simply glorifying a platform shortcoming (i.e. not being able to release
entity objects thus forcing the use of session objects) into full fledged
paradigms of EJB usage.
VERY IMPORTANT NOTE: Since wrapping of entity beans into session beans is a
usage paradigm and the above conceptual flaw is a platform characteristic,
the EJB architecture (and spec) is not questioned. Furthermore, session
beans are complementary to entity beans and both are necessary for
implementing feature complete solutions.
Imre Kifor
Valto Systems
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