Sometime ago, i asked on SO a question that include if i have to implements my service as they're using JPA managed entities ? Here are the two points of my own answer that should interest you :

• I don't have to abstract the fact that i use managed entities, this will lead to complex and unefficient code

• I choosed JPA, i won't switch for it which is true unless rewriting the full model to stand for something based on non relationnal database.

If you try to abstract the fact that you're using lazy-loading/managed entities, you will just have troubles. For instance, i saw a project where there was DAO Pojo and business POJO, they were always converting the DAO to business POJO using adapter, and thus always triggering loading lazy list in the N+1 select way.

So if I adapt what i was told in that question, at the very least, your should have 2 differents business implementations, one relying on the strength of JPA, and the other, either one that don't care about JPA/RDF, either one that will get the best of RDF DAO layer.

I know that doesn't seems to follow the rule of POO about totally encapsulating behaviour in each layer, but really, try to abstract complex JPA model without triggering cascading N+1 select on every relations or manually fetching each relations when you shouldn't need to with JPA. It just can't work. JPA is really invasive, but really powerful too, as you have very few code to write (and maintain!) to use it.

Of course if you're just doing something really simple having quite few data, a demo, ... you can stick to one business layer that is not using JPA at his best.

But if you need some basic performance, like loading all your database line-by-line in the ORM is not an option, you will probably end up stuck with one implementations that don't use JPA right.

Sometime ago, i asked on SO a question that include if i have to implements my service as they're using JPA managed entities ? Here are the two points of my own answer that should interest you :

• I don't have to abstract the fact that i use managed entities, this will lead to complex and unefficient code

• I choosed JPA, i won't switch for it which is true unless rewriting the full model to stand for something based on non relationnal database.

If you try to abstract the fact that you're using lazy-loading/managed entities, you will just have troubles. For instance, i saw a project where there was DAO Pojo and business POJO, they were always converting the DAO to business POJO using adapter, and thus always triggering loading lazy list in the N+1 select way.

So if I adapt what i was told in that question, at the very least, your should have 2 differents business implementations, one relying on the strength of JPA, and the other, either one that don't care about JPA/RDF, either one that will get the best of RDF DAO layer.

I know that doesn't seems to follow the rule of POO about totally encapsulating behaviour in each layer, but really, try to abstract complex JPA model without triggering cascading N+1 select on every relations or manually fetching each relations when you shouldn't need to with JPA. It just can't work. JPA is really invasive, but really powerful too, as you have very few code to write (and maintain!) to use it.

Of course if you're just doing something really simple having quite few data, a demo, ... you can stick to one business layer that is not using JPA at his best.

But if you need some basic performance, like loading all your database line-by-line in the ORM is not an option, you will probably end up stuck with one implementations that don't use JPA right.