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Re: [eclipselink-users] EntityManager.remove does not remove entity from cache
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Tom,
I see where you're coming from. The spec references that you gave do
seem to support this behavior (unfortunate, but that's an issue for a
different list). But, I think you then run into other conflicts with the
spec. For example, contains on that the removed entity will return true
after retrieving it with the query.
Section 3.2.5
The contains method returns true:
• If the entity has been retrieved from the database, and has not been
removed or detached.
• If the entity instance is new, and the persist method has been called
on the entity or the persist
operation has been cascaded to it.
The contains method returns false:
• If the instance is detached.
• If the remove method has been called on the entity, or the remove
operation has been cascaded
to it.
• If the instance is new, and the persist method
mike
mike
Tom Ware wrote:
The spec references I have found are in section 3.2.3 of the JPA 1.0
specification:
Reference 1:
---
Bidirectional relationships between managed entities will be persisted
based on references held by the
owning side of the relationship. It is the developer’s responsibility
to keep the in-memory references
held on the owning side and those held on the inverse side consistent
with each other when they change.
---
Reference 2: (for flushing)
----
The semantics of the flush operation, applied to an entity X are as
follows:
<snip>
- If X is a removed entity, it is removed from the database. No
cascade options are relevant.
----
Is there something I am missing in the spec that you can point me to?
-Tom
Mike Traum wrote:
Maybe I've been defining my entities strangely, but if you define a
@OneToMany on A and then a @ManyToOne on B (pointing to A), the
schema generated by eclipselink will have the foreign key in B
pointing to A. So, this will not be enforced by the database. I can
drop in some code to illustrate if desired.
If the above is not funky, I think, by the JPA spec, the DB delete
should not occur. Otherwise, the relationship 'magic' will occur
between app restarts but not within app queries.
mike
Tom Ware wrote:
EclipseLink relies on your DB foreign-key-contstraints to enforce this.
i.e. You should get a SQL exception on the remove if a
foreign-key-constraint exists for this relationship.
Mike Traum wrote:
Yes, I thought that might be the answer. But, the implementation
seems odd. JPA doesn't provide magic for this, but it is deleted
from the database, however the cache is maintained in a stale
state. It seems to me that either it should not be deleted from the
database or it should be removed from the cache.
mike
Tom Ware wrote:
Hi Mike,
You need to sever the relationship between an A and a B before
you remove B. JPA does not provide any magic for this.
-Tom
Mike Traum wrote:
I have the following enitiy map:
A->B->C (where -> represents a OneToMany relationship)
If I do a EntityManager.remove on a B, a following Query (select
all) will still return that entity, even though it has been
removed from the database.
Any ideas on the proper way to handle this?
Here's some code illustrating the issue:
EntityManager em = emf.createEntityManager();
Query q = em.createQuery("select a FROM A a");
List<A> as = q.getResultList();
em.clear();
em.close();
System.out.println(as.get(0).getChildren().size()); // output
is 2
B b = as.get(0).getChildren().get(0);
em = emf.createEntityManager();
em.getTransaction().begin();
B bm = em.merge(b);
em.remove(bm);
em.getTransaction().commit(); // successfully removes B and
children from database
em.clear();
em.close();
em = emf.createEntityManager();
q = em.createQuery("select a FROM A a");
as = q.getResultList();
em.clear();
em.close();
System.out.println(as.get(0).getChildren().size()); // output
is 2
em = emf.createEntityManager();
q = em.createQuery("select a FROM A a");
((ReadAllQuery)((EJBQueryImpl)q).getDatabaseQuery()).refreshIdentityMapResult();
as = q.getResultList();
em.clear();
em.close();
System.out.println(as.get(0).getChildren().size()); // output
is 1
Thanks,
Mike
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