Very useful - nice work - might be worth mentioning this in the EJB3/Hibernate
forums as it far less confusing than the Hibernate EntityManager reference
manual.
anonymous wrote : One of the properties must be an Id (mostly a Long) and the
class itself must be annotated with @Entity.
Why a long? (Not come across this before)
anonymous wrote : This needn't happen immediately, he might keep your entity
in the cache and write it to the database later.
By default flushes occurs at the method boundary.
anonymous wrote : (Just by the way: Whenever a RuntimeException occurs during a
transaction a rollback is performed and all changes to data get revoked).
Just RuntimeException? Not all exceptions? Is it EJB3 or the
SeamExceptionFilter that does the rollback?
anonymous wrote : So there's an easy solution: We extend the lifetime of the
persistence context so that the entities remain managed during calling multiple
transactions/methods. Therefore we change the injection of the EntityManager:
| @PersistenceContext(type=PersistenceContextType.EXTENDED
| | private EntityManager em;
| Now the managed entities "live" in an Extended Persistence Context
The Seam Managed Persistence Context takes this further and provides a
conversation scoped entity manager. This prevents Lazy Initialisation
Exceptions from occuring when accessing entities from earlier requests.
It needs to be set up in components.xml (see the Configuration section of the
reference doc), and then can be accessed via (where mySMPC is the name it was
configured under)
@In(create=true) private EntityManager mySMPC;
anonymous wrote : ..."from Entity where lastName=".nameToSearchFor." order by
firstName"
It is recommended not to do this but to do
em.createQuery("select e from Entity e where e.lastName = :lastname order by
e.firstName").setParameter("lastName", lastName).getResultList();
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