So theoretically, a merge will also persist?
Actually I started out this project assuming it would, but because it has to
work with TopLink as well OpenJPA, I stopped using merge() when I came across a
bug in the TopLink implementation.
But TopLink aside, thanks for the reminder.
Michael Dick on 07/04/08 17:06, wrote:
It looks like the persist is being cascaded to the detached entity. If
that's the case then we're throwing the exception per these bullets in the
JPA spec :
3.2.1 Persisting an Entity Instance
A new entity instance becomes both managed and persistent by invoking the
persist method on it or
by cascading the persist operation.
The semantics of the persist operation, applied to an entity X are as
follows:
<snip>
• If X is a detached object, the EntityExistsException may be thrown
when the persist
operation is invoked, or the EntityExistsException or another
PersistenceException
may be thrown at flush or commit time.
• For all entities Y referenced by a relationship from X, if the
relationship to Y has been annotated
with the cascade element value cascade=PERSIST or cascade=ALL, the persist
operation is applied to Y.
If you were to merge the new entity instead of persisting it then the merge
action would be cascaded to the parent entity. It would become managed, but
that might be one way to resolve the issue you're hitting.
-Mike
On Mon, Apr 7, 2008 at 7:09 AM, Adam Hardy <[EMAIL PROTECTED]>
wrote:
I've got an issue with the persist operation, when I use a detached entity
as one of the entity's referenced entities.
OpenJPA throws the
org.apache.openjpa.persistence.EntityExistsException: Attempt to persist
detached object
"[EMAIL PROTECTED]
".
The situation is this: my MVC layer has received a new entity which it
must create. The parent entity for this is found in a cache, in a detached
state.
What I'd like to know, is why is JPA forcing me to merge this detached
entity before allowing me to persist the new child?
It means I can't use the cache, or I have to program the DAO to merge all
referenced entities. This latter option seems like a job that JPA should be
doing. JPA knows this parent is a detached entity, so why can't it merge the
managed entity?
I can't see any text in the EJB spec that would mandate this behaviour,
yet Hibernate does it too.
