[eclipselink-users] Looking for the ORM that best matches my needs

["Francisco P." <luxspes@xxxxxxxxx>]

My first contact with an ORM was NextStep EOF... an ever since I have felt
that nothing compares to it .

The thing is, I have had to work with JPA/Hibernate for a few years now...
and I feel it has some weaknesses I really do not like, I am thinking about
"switching to something else" but first i would like to be sure that the ORM
I switch to does not have this weaknesses too. 

List of weaknesses in JPA/Hibernate: 

-No way to manage an object that "will be persisted", in JPA/Hibernate if
you call entityManager.persist(object) and the database does not support
sequences (like MS-Sql) an insert will be triggered, and if any of the non
nullable fields of the objects is null, it will crash. If your object has a
compound primary key, things get worse, because the entityManager can not
deal with it until the compound primary key is set, and if your compound
primary key is formed by foreign keys pointing to objects that are new too,
that means you will not be able to save stuff with with a simple single call
to entityManager.persist to one of the objects, cascading will not help you
(I really miss something "magic" like the single shot
EditingContext.commitChanges() in EOF)

-No easy way to know if "an object is dirty" (if it has changed/deleted
since it was read from the database, there is just no API for that), and
since you can not know what objects will be persisted, and what object have
changed, and what objects will be deleted from database, that means you can
not easily create an unified API for centralized polymorphic validation
(that is no easy way to create validateForSave, or validateForDelete methods
in your persistent entity classes)

-No real equivalent for validateForXXX, JPA lifecycle callbacks are not
match for validateForXXX because you can not query the database during the
lifecycle callbacks, and if you throw an exception inside a lifecycle
callback, the JPA/Hibernate entityManager enters an invalid state, and after
that you can not continue to use your POJOs, you have to start over with a
fresh entityManager... and without you modifications to the POJOs. Note that
Hibernate new validation framework does not offer a real solution for this
problem... and AFAIK JSR-000303 will not help with this either.

-No support for some kind of temporary id: In JPA/Hibernate, the id for an
object is "null" until you flush it to the database, so if you need to
reference a particular object instance from the user interface... there is
plain no way to do it, you have to "save it first" to get a primary key.

-No support for Nested Contexts... ( I think they would be a perfect fit for
conversational frameworks like Seam or Shale). One of the goals of the
ObjectContext is to provide an isolated area where local object changes can
be performed without affecting other similar areas or the underlying
storage. Nested Context changes can be saved to the parent Context without
saving them to the database. Such child context is often called "nested".
Nested contexts are useful in many situations, such as nested UI dialogs,
complicated workflows, etc.

Those are my main disagreements with the way I have to work with
JPA/Hibernate... will switching to
JPA/EclipseLink help me with those? Apparently Cayenne, another ORM still in
its way to become JPA complaint does not have any of this weaknesses (see
http://www.nabble.com/Coming-from-EOF%3A-Cayenne-vs-Hibernate-to22463349.html
for the answer to a very similar question in Cayenne forum), so I have been
wondering... are this limitations an intrinsic part of the JPA standard and
therefore EclipseLink shares this weaknesses (and Cayeenne will have to act
as if were limited by them too while used with the the JPA complaint API) ,
or are this abstraction leaks in the way JPA/Hibernate works that are not
shared by other JPA implementations (like EclipseLink)?

Thanks,

Regards,

LuxSpes
-- 
View this message in context: http://www.nabble.com/Looking-for-the-ORM-that-best-matches-my-needs-tp22474341p22474341.html
Sent from the EclipseLink - Users mailing list archive at Nabble.com.