Hi all,
I'm right now having to deal with some tough design decisions concerning
Data Access Objects (DAOs). I know this is really not a direct related
Struts question, but I also understand that everybody in this list already
faced this issue while integrating Struts in their model.
I'm not using EJBs but this should really not be an issue, as the DAOs are
supposed to be reusable in non-EJBs designs as well. What I have is struts
dealing with controllers, and these controllers dealing with business ojects
and DAOs. Let's see what I found/have:
- J2EE Pet Store, in their DAO objects, for every new business method, they
get a new connection from the pool and later release it. This makes the code
cleaner at the controller side, but VERY repetitive at the DAO side (note
that they replicate the getConnection,closeConnection, closeResultSet,
etc... all over the DAOs. It's kind of amazing to see such a replication in
a reference implementation. It also sounds very, very expensive to get a new
connection every time. In some cases, a business method makes a call to
another business method, and they are getting the connection twice for this.
Imagine a call where the controller needs to talk to 3 DAOs and perform
about 10 business method calls. They will get and close the connection 10
times. The connection pool, managed by the application server, will more
than likely create a bottle neck in this whole thing.
- in my approach, while testing, the controller is responsible for getting a
new connection and forwarding it (through parameters) to the DAOs. The
problems with this approach are: the DAOs are not a member of the Business
objects, but work in parallel with them. Thus, the controller deals with
both the business objects and the DAOs, and makes all the "control", serving
also as a bridge, or facade. The advantage of this approach is that
basically, for every user request, you will have only one connection lookup,
doesn't matter how many DAOs methods you call from different objects in
order to full fill the request.
I need to confess I'm lost. The PetStore approach sounds cleaner in some
sence, but also sounds too repetite in other, and mostly, sounds way to
expensive (or it isn't?).
How do you see all this?
Regards,
Vanderlei
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