There are many many messages concerning this in the archives of the
EJB-INTEREST list, available from Sun. Having said that, let me
summarize a few known issues with CMP.
The concept of CMP itself isn't bad and is very usable in some
situations, primarily when there is a 1:1 mapping between objects and
tables in a relational database. This is true either for small systems
or for portions of large systems.
The main issues I see with CMP are as follows:
1. If used extensively in a large scale system, this can lead to a very
inefficient object design (too fine-grained). This will almost always
result in a system that performs poorly and does not scale well.
2. The EJB 2.0 specification will address much of the 1:1 mapping issue.
I think, however, that another issue will become prevailent. That issue
being that CMP ties the hands of the developer in tuning the SQL
statements that access the database. As a result, it will be difficult to
tune an application to perform as required.
These two issues are important because when evaluating where an
application spends its time, typically 70% or more of the time spent is
in communicating with the database. This being the case, you want all
the flexibility possible for reducing the number of requests to the
database and also for making sure that those requests are well tuned.
Scot.
>>>>>>>>>>>>>>>>>> Original Message <<<<<<<<<<<<<<<<<<
On 12/7/00, 11:02:11 AM, Hunter Hillegas <[EMAIL PROTECTED]> wrote
regarding [jBoss-User] CMP:
> Thanks for everyone's input on the Small App vs. Large App question. I
got
> some good info. There's no need to continue bothering the list with it.
> I do now have a question about CMP vs BMP. This may not be the right
place
> to ask this question. If not, please direct me to another list or Web
site
> resource...
> In the Sun training I did for J2EE they were claiming that CMP was really
> great (obviously - they worked for Sun!).
> I get the impression from y'all that it's not all it's cracked up to
be...
> Why is this? What's wrong with it?
> It seems like a benefit. Does it not work well?
> Hunter
> --
> Hunter Hillegas
> [EMAIL PROTECTED]
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