Design Patterns discussion

[Patrick Plaatje <patrick AT ipros.nl>]

Hi all,

im fairly new to design patterns, but have read my share on the subject 
already. I am aware that not all programming needs design patterns, but 
i've come to a point where i could use a little help in solving a 
problem i am facing. Although i am not sure if i should post this, but 
if not, i hope someone can push me in the right direction.

I am implementing a data layer in my application, which on it's turn 
will be based on the JSR-283 specification (Java Content Repository). So 
with an existing package of interfaces i am trying to develop an 
independent storage (data) layer. The intention is that data can be 
stored on local disk, webdav, database, etc. When 
googling/reading/trying i finally came across Sun's Core J2EE pattern 
library. Here they have a pretty interesting pattern which could solve 
my challenge: the Data Access Object. So i started off implementing this 
design, but soon enough it stroke me that it was really a lot of work 
implementing this, and i'm starting to think that this might not be the 
way to go. Here's what's happening:

I am creating an abstract class: the DAOFactory, which is extended by 
the Data Layers (LocalFileSystem, WebDav, DB). These specific datalayers 
have methods which return a specialized object which knows how to deal 
with the actual object (loading/saving/etc). This sounds fairly simple 
and easy to do, but when i implemented this, it actually results in 
very, to my opinion, bloated code. Because for each specific 
datastore(-source) the domain objects need their specific implementation 
and when a new domain object is introduced, i will need to modify all 
datalayer classes.

I was wondering if someone had some thoughts about the preceding? I'd 
really appreciate anyone's opinion on this. If you need more info or 
actual code, please leave a reply.

Thanks in advance & best regards,

Patrick