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entitymanager.close() doesn't destroy persistence context in SE application [message #523475]

Fri, 26 March 2010 11:02

Eclipse User

Closing an EntityManager should result in destroying the persistence context according the specs, but this doesn't seem to be the behavior in a SE application.

The following example results in only one query to the database, instead of two.

EntityManagerFactory factory= Persistence.createEntityManagerFactory("testjpa");			

EntityManager em;

em=factory.createEntityManager();			

Contact peterFromDB=em.find(Contact.class, 1);
em.close();

em=factory.createEntityManager();
Contact peterFromDB=em.find(Contact.class, 1);
em.close();

factory.close();

The example does the following:
-Create an EntityManagerFactory.
-Create an EntityManager
-Do a find
-Close the EntityManager (the persistence context should be gone now...)
-Create a new EntityManager
-Do a find again (this should just be new query to the db, there is no "cache" any more).

There is no second level cache configured. From the specs I understand this behavior is wrong.

Quote:

The EntityManager.close method closes an entity manager to release its persistence context and other resources.

It happens both with EclipseLink 1.2 and 2.0.

Re: entitymanager.close() doesn't destroy persistence context in SE application [message #523484 is a reply to message #523475]

Fri, 26 March 2010 06:26

Eclipse User

What happens if you add this option as the second parameter when configuring the EMF?

Map<String, Object> lOptions = new HashMap<String, Object>();
lOptions.put(PersistenceUnitProperties.CACHE_SHARED_DEFAULT, "false");
EntityManagerFactory lEntityManagerFactory = Persistence.createEntityManagerFactory("testjpa", lOptions);

Re: entitymanager.close() doesn't destroy persistence context in SE application [message #523488 is a reply to message #523484]

Fri, 26 March 2010 11:27

Eclipse User

With this option set it works as expected (two queries). To my opinion this is not according to the JPA specs, allthough it might be a useful optimization.

Re: entitymanager.close() doesn't destroy persistence context in SE application [message #523501 is a reply to message #523488]

Fri, 26 March 2010 11:45

Eclipse User

> With this option set it works as expected (two queries). To my opinion
> this is not according to the JPA specs, allthough it might be a useful
> optimization.

I also found that with a standalone application (I have a swing app) this setting is unwanted. But with a single channel access, like a webapplication, this will give some serious speed benefits. So it is a useful feature, but maybe it should be off by default, because it produces unexpected results.

Tom

Re: entitymanager.close() doesn't destroy persistence context in SE application [message #523502 is a reply to message #523501]

Fri, 26 March 2010 12:02

Eclipse User

I agree, it might lead to stale data for example. The downside of setting it to false by default is that most people will probably not set it to true, while it might be useful for most applications.

Because it's not really according to the specs I still believe it should be false anyway however.
Thanks for the fast answers btw Smile

Re: entitymanager.close() doesn't destroy persistence context in SE application [message #523611 is a reply to message #523502]

Sat, 27 March 2010 03:32

Eclipse User

> Thanks for the fast answers btw :)

No problem.
I have a question pending here myself and had to keep an eye if anyone had responded. :-)

Re: entitymanager.close() doesn't destroy persistence context in SE application [message #523739 is a reply to message #523475]

Mon, 29 March 2010 02:41

Eclipse User

I filed a bug for the issue: https://bugs.eclipse.org/bugs/show_bug.cgi?id=307342.

Re: entitymanager.close() doesn't destroy persistence context in SE application [message #523832 is a reply to message #523739]

Mon, 29 March 2010 10:46

Eclipse User

In the provided example the Contact is being loaded from the shared cache and registered within the new Persistence Context. The original Persistence Context has been destroyed. You can verify this by keeping the reference to the original Context instance after closing the Persistence Context and changing an attribute of this instance. You will be able to verify that the subsequently found instance does not have this change.

You can turn EclipseLink caching off using the mentioned Persistence Unit property or through the JPA 2.0 cache settings and API however be aware that there may be a performance cost in disabling the cache.

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