Hello Ingo,
I'd like to even further summarize your comparison, since I think you do mention a
few issues that should fall under the same category.
Why use CMP?
* Simplicity
* Performance
* Database portability
Why use BMP?
* Full control
My conclusion is that BMP should only be used when you really do need full control,
for any of the reasons you mention. Otherwise, use CMP.
>
> I have summerized the pros and cons regarding CMP and BMP from posings on
> this list. Please send your comments, tell me if you have a different
> opinion in certain points or if I missed something important.
>
> Pro BMP:
> * Ability to express complex relationships among data.
> Contra CMP:
> * Difficult to use with complex database schema.
I have to comment on this issue since I think it's often described as a bigger deal
than it really is. I agree that CMP might not give you the control you need at all
times, but in a decent container you can express pretty complex relationships.
<vendor>
In the Orion Application Server you can have many kind of relationships between
entities. You can (of course) keep entity bean references directly in another
entity bean, but you can also keep a Collection of entity beans (or a List, a Map
or a Set). This does provide pretty strong support for complex relationships. Of
course, until this is standardized it will be dangerous to use, but this is a
temporary problem.
</vendor>
>
> 1. Does a container, as a matter of principle, have more facilities to
> optimize the persistence (e.g. only the container has knowledge which
> other transactions are currently running -> run-time optimizations). If
> yes, the consequence would be that sooner or later CMP _will_ be the
> alternative with the best performance?
>
Yes, the more abstract the description is, the more the Container can step in and
optimize things.
This is of fundamental importance and is why HotSpot can perform so well and why
it's hard to write assembler-code that is faster than the code generated by an
optimizing C compiler. It's easier to optimize higher-level descriptions.
>
> 2. Are containers really not mature yet (in a sense that BMP is still much
> faster than CMP)?
>
<vendor>
I can only speak for Orion, but in our tests, CMP is normally much faster than BMP
today. I'm sure this is the case with some other servers too, and will be the case
for all once they employ all possible optimizations.
</vendor>
Regards,
Karl Avedal
The Orion team (http://www.orionserver.com)
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