At 17:11 23.07.00 , you wrote:
>Hi,
>
>I had a discussion with a colleque of mine and we did not reach a agreement,
>maybe some experts on this mailing list can help us out....
>
>The question is: Should you use database level constraints to enforce the
>integrity of the database or is the integrity of the database the
>responsibility of the EJB?
Most definitely yes. Not using a proven mechanism such as database
constraints to enforce constraints in your model to me would be like not
wearing your seatbelt because you are afraid of wrinkles in your suite.
Even if you enforce your constraints at the EJB level, why not use the
extra safety that database constraints provide. I would view them on the
same level as asserts in your code. The only thing I can think of, that
would be a con is that you might have some extra maintenance work because
if your model constraints change, the db constraints also have to change.
from my personal experience I'm completely pro using db constraints as they
have helped discover numerous bugs in the EJB code in projects I've been
involved in. at signal7 we use a homegrown code-generation suite that
generates both database definition including constraints and EJB entity
bean code including relationships and deployment files from a consistent
model so we don't even have the extra maintenance effort. one could
argue about using cascading deletes and triggers because they can cause
problems with EJB caches but just enforcing constraints in a (relational)
database model has helped us considerably in our projects.
>My collegues opinion is that it is the responsibility of the EJB to enforce
>the integrity of the data in the database. If you would implement this in
>constraints in the database then both the EJBs and the database would have
>to know about the integrity rules. Which is duplication of knowledge/logic,
>which is not a good thing.
it depends, see comment above about maintenance and code generation.
>At first I agreed with him, but now I have second thoughts:
>- What if the database is used by other (non J2EE) applications? The
>integrity then must be maintained by the database, or should all
>applications be held responsible for the integrity? The latter would mean
>distributing the reponsibility over multiple applications, which is not a
>good thing? This would advocate to put the responsibility in the database
>and define the constraints there.
>- By putting the constraints in the database you enforce that their is one
>place where the data is consistent. Specific application could add
>additional constraints for that application into their logic, as long as it
>does not conflict with the data model.
>
>I'm anxious to hear your opinions on this....
>
>Regards,
>
>Gero Vermaas
>
regards,
robert
(-) Robert Kr�ger
(-) SIGNAL 7 Gesellschaft f�r Informationstechnologie mbH
(-) Br�der-Knau�-Str. 79 - 64285 Darmstadt,
(-) Tel: 06151 665401, Fax: 06151 665373
(-) [EMAIL PROTECTED], www.signal7.de
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