Assuming that concurrent access is not a major factor, can someone
explain to me what the benefits of using entity beans are, as opposed
to a basic object->relational mapping?
My company is currently embarking on its first major project involving
EJB, and I and the others involved in designing the system have been
working hard getting up to speed in the technology. (We already have a
good background in OO Design, Java and RMI.) The more we learned about
entity beans, the more we began to ask ourselves, "why are we using
these?" Ultimately we decided to simply abandon them altogether, and
use the EJB container primarily for transaction management, while
passing serialized data objects back and forth between the server and
clients.
One of the most hyped features about entity beans has been CMP, but
unless we're missing something, that seems to be a joke, not nearly
sophisticated enough to meet our needs. And even if it did, all it
would save us is time and effort, and that's not one of our overriding
goals in building this system, it's performance, stability,
scalability, etc. As it happens anyway, we already have a homegrown
code generator that, given a DB table's metadata, will generate a
matching data object class, a class to do all of the basic CRUD
chores, and a session bean (with the attendant interfaces) for
accessing it, so CMP would not even save us a great deal of work.
Another thing that had us scratching our heads was, a great deal of
the literature pertaining to entity beans is about ways you can work
around their excessive overhead, like network chattiness, excessive
hits on the database, scalability issues, etc., and some of these
workarounds, e.g. Monson-Haefel's "bulk accessor" methods just seemed
clumsy and awkward. If there are so many pitfalls and gotchas
associated with entity beans, why on earth does anyone use them?
The only problem we could think of that entity beans might provide an
elegant solution to was situations where many clients would be
concurrently accessing a single entity bean, and you want one user's
modifications to be visible immediately to clients (as soon as they
call the changed property's getter method, that is.)
I hope no one misinterprets this post as an anti-Java or anti-EJB
troll. Believe me, I love just about everything else about Java and
J2EE. In fact, I would be happy if someone who has some actual
experience with entity beans could enlighten me if there is some great
payoff in using them that I've missed.
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