My company has most of it's Business data already in relational databases.
We've decided to use EJB's on our AppServer. As I look at designs which
extend and reuse what I've got, I'm concluding the following:
* Entity Beans (CMP)
- I should not use these if the underlying database is being updated by both
the EJB and my non-EJB systems, due to Data dis-integrity issues caused by
"out-of-synch" cache.
- For portions on my systems that are "Read-Only" or "net-new" this is fine.
* Entity Beans (BMP)
- I should use a non-cacheing implementation, unless I can guarantee
synchronization with the updates generated by the non-EJB systems on the
underlying DBMS.
* Session Beans
- I can use JDBC inside the session bean. This is essentially a BMP without
a Finder Method. I have total control over the Business Interface(s) offered
by my Session Bean. I can use a seperate interface for each role played by
my session bean.
I'm tending toward the Session Bean approach for the following reasons:
1. I have full control over the Interface(s) offered by the Bean. From a
multiple release cycle, as my deat requirements change, this allows me to
keep prior interfaces available without being impacted from business domain
type changes.
2. I don't want any Session Beans other than ours accessing the database. I
could rely on administrative security on Entity Beans, but the Session Bean
approach seems to ensure that the architecture is not comprimised, where the
Entity Bean approach allows un-informed administrators to grant access to my
entity beans potentially comprimising the architecture. Before long there
will be client UI's directly calling my Entity Beans. Since my Business has
been involved in many acquisitions, my Business domain types are often
impacted. This appears to me to have a ripple effect into the Interface of
any Entity Beans that I build. Thus due to the cohesion created by client
access the potential change impact on consumers of my entity bean seems very
large.
Am I missing something?
David Marshall
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