Evgeny,
i have the same app layout when it comes to DAOs and detachment when
communication with business layer but i dont know if i would do it
again. You should consider making the business logic EntityManager-
aware as Patrick said. This way you have the full set of features
like lazy loading and stuff. Furthermore its more performance
friendly because most likely (in your and my scenario) you are going
to re-attach the object because of persisting or updating it in the
DB and this will definitely cost performance.
--
regards
Marc Logemann
[blog] http://www.logemann.org
[busn] http://www.logentis.de
Am 12.09.2007 um 11:04 schrieb Evgeny Shepelyuk:
The idea is that Toplink JPA supports that feature. OpenJPA - no.
Maybe this can be done as some configurable behaviour ?
They do, but really, all that they are doing is hiding the open
EM. In
other words, the objects are not actually really detached yet.
What type of application are you building? Most server frameworks
these days have some sort of request boundary concept, such as a
ServletFilter; given such a concept, it's trivial to register an EM
with a ThreadLocal or some equivalent construct at the beginning of
the request, and close the EM when the context closes.
It's not web application but rather some core service processing
request
coming into it by RMI, REST/HTTP and even SOAP :)
Now we're in the middle of migration to JPA from custom ORM layer.
And just wanna separate "business logic" classes from JPA stuff
completely.
We can easily avoid loading of field of detached entites writing
smth like that
OrderEntity order = .... ;// passed detached entity from some DAO
UserEntity user = new UserDAO().get(order.getUserId());
but i think more convenient way will be following :)
OrderEntity order = .... ;// passed detached entity from some DAO
UserEntity user = order.getUser();
Problem is that for example i have one class that makes some DB
operation and it's used from
several internal clients. Those clients are asking for some entity,
then ask for it's dependants etc.
And i'm kinda unwilling to inject EntityManager into those top-
level classes.
--
Best Regards
Evgeny K. Shepelyuk
