Your DAO object will probably be quite lightweight and you can link it's
construction/destruction to the entity bean instance (to reduce how often
you are constructing/destructing it). Anyways, I wouldn't spend a lot of
time worrying about the cost of constructing the DAO. Premature
optimization is a bad thing.
Cheers
-----Original Message-----
From: J. Babu
To: [EMAIL PROTECTED]
Sent: 9/21/01 12:37 PM
Subject: Bmp with DAO
All,
Any comments on the following design.
Requirements: System should support transacation, large number of
Clients
, performance and business layer -Persistence layer isolation.
Scenario 1:
Let Session Beans call directly DAOs.
It fulfills all the above requirements excecpt maybe little performance
hit,
as SessionBeans starts transaction and DAOs does
insert/delete/update/search
operations. For each call, DAO instances are created and destroyed at
the
end.
Drawbacks:
Both business layer and perrsistence layer has
to be
in the same machine.
Scenario 2:
Let Session Beans call directly to singleton DAOs.
It also fulfills all the requirements, but not sure about thread safe
of
Singleton objects, as all the session beans ( concurrent threads) use
the
same instance of DAO, for insert/delete/search/update operations,
without
having any class variables.
Drawbacks:
Both business layer and persistence layer has to be in the
same
machine.
Not sure about Thread safe of DAOs.
Scenario 3:
let session beans call to BMP which inturn calls singleton DAOs. BMPs
offer transaction and caches the data if required, and uses the
Singleton
DAOs for all access to DB or any persistence service.
Drawbacks:
Not sure about Thread safe of DAOs.
Scenario 4:
Let session beans call to BMP which inturn uses DAOs. In this case,
for
each call from BMP, new DAO instance is created.
Drawbacks:
Performance of system may go down, as each client call
ends
up creating new DAO instances.
I appreciate all you guys valuable comments. In all the above
scenarios, I prefer scenario 4, as it suits all the above requirements,
except small hit on memory and perfromance.
Thanks,
Babu
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