JBossDeveloper

Yes but when would this JNDI entry be registered?

Sorry for bothering you time after time but if I havent misunderstood it's the actual @PersistenceContext annotation that does the registration of the JNDI entry?
And one cannot use a attribute-less @PersistenceContext when using multiple EM's - hence the JNDi entry must be registered by something else (my wild guess the persistence.xml interpreter at doploy time)?
And then in the code one could do a JNDI lookup without the use of @PersistenceContext annotation to find the EM based on a name supplied by the caller or some other smart enhancement that does not make it nessesary to hard code the attributes to @PersistenceContext.

"kabir.khan@jboss.com" wrote:
I think this is the (missing) bit of functionality you're after. http://www.jboss.org/index.html?module=bb&op=viewtopic&p=3883141#3883141

Should be there in the final release

We need that as well...but that won't solve the issue of this thread since one still cannot specify "name" of the EM dynamically for a container managed app.

I've studied the spec thoroughly now to see if I could use the EntityManagerFactory and pass the "name" to it at runtime, but all the examples (se chapter 5.5.1 to 5.5.6) and all the descriptions only shows this approach for application managed persistence outside of the app server :-(

All the container managed persistence examples that uses the EntityManagerFactory uses injection with annotations and hence - impossible to send in name as a variable.

I even tried coding an app which has a service that during startup loads mappings between the names declared in the persistence.xml's and user defined names into a hashmap. One can after that always on the fly get the apropriate entity manager name from that service based on what the caller sends in. I then used the "out of container"

 EntityManagerFactory emf = Persistence.createEntityManagerFactory(strCallerPassedNameOfEntityManager);

 EntityManager em = emf.createEntityManager();

Eventually we'll have a global JNDI lookup and/or XML injection. So why do you keep harping on this? It is not that big of a deal....

In the meantime, why don't you just create a Session bean that implements the locator pattern?

@Stateless
public class EMLocatorBean implements EMLocatorLocal {
 @PersistenceContext(...)
 EntityManager em1;

 @PersistenceContext(...)
 EntityManager em2;

 public EntityManager getEntityManager(String name) {
 if (name.equals("EM1")) return em1;
 ...etc...
 }
}

Sorry but I was "harping" because this is a forum and because I wanted to have a discussion that got me the following answer:

http://www.jboss.org/index.html?module=bb&op=viewtopic&p=3884496#3884496

which actually solved the "select entity manager at runtime" issue.

When the next release comes with the persistence.xml's "reference" (<jar-file> and ) functionality implemented - the issue that one must have the same entity bean within several .par archives are also covered :-)

Best regards

Jon,

thanks for pointing me to this post. I also have the same need: add DataSources at runtime (rather than at compilation, like the examples show), and also not have to repackage my ear file for that.

If you come accross a good (or any!) solution to this, please post!!!!

Also let me know if there's a bug opened (that I can vote for) to have this on the radar screen...

Zorzella

Sorry for my prior reply: I somehow missed the last post which seems to have a solution for runtime-selecting the EM.

As for the procedure to deploy, does one need to repackage the .par file with all the same beans and a new persistence.xml that points to different data source, and declares an entity manager with a different name? And then one would use that code snippet to choose the EM based on the name?

Is that it?

Thanks,

Zorzella

Well yes...In my case. I coded a service bean (clustered singleton) which sort of "loads" my own xml mapping file of sitenames (key) and entitymanager names (value) into a thread safe Properties object in memory.
This service bean is accessible from all my session beans.
Each time I want to add a new site (read database) I do that in the service beans management interface through the JMX console at runtime (it stores another key/value in my xml mapping file and in the in memory Properties object).

Then for each table I have an entitybean. Although it is actually the same bean for all the corresponding tables within the different site's databases.

The session bean that calls the entity bean has no @PersistanceContext or similar code , but it calls the service bean with the callers sitename to get the entitymanager name from its in memory "mapping".
Then it calls a method similar to the one posted by triathlon98 to lookup the actual entity manager based on the name recived from the service bean at runtime.

This way the only thing I have to do to add a new database and make my solution work without any coding / recompiling etc is that i deploy a .par with a new persistence.xml (could also be programmaticly automated) and then I register it in JMX console through my service bean.

The only thing that is still a bit clumpsy is that it seems to me that until the "jar-file" and "class" functionalities of the persistence.xml files are implemented, there is no way to have the single entity bean packaged and deployed only once. Hence, one has to copy the entity class file into all the .pars that is about to use it rather than just referencing to it which in the future will be possible.
Let me know if you find a better solution for this.

Good luck.

I had pretty much the same design in mind, though I'm thinking on having a "master" datasource, with a single table doing the job of your Properties file.

Anyway, thanks for all the info. Let us know when/if you ever get the jar ref working (i.e. after it's implemented, of course).

Zorzella

I will be adding a global jndi lookup for managed EntityManagers, managed EntityManagerFactory's. This should solve your problems.

The EntityManager.xxx is non viable as EntityManager is and should stay an interface.

the javax.persistence.Persistence class gives that capability but it really should only be used outside of the container as the EntityManager's created will not be managed by the app server.

I can obtain an EntityManager dynamically using the above techniques but whichever technique I use I can't cast the resultant EntityManager to a org.jboss.ejb3.entity.HibernateSession.

Is there a way to get hold of an EntityManager dynamically that will cast to a HibernateSession (as described in the Hibernate Integration document (chap 2))?

Look in the docbook.

http://docs.jboss.com/ejb3/reference/build/reference/en/html/hibernate.html

The next release I will allow the direct injection of Hibernate Session and SessionFactory. These will be proxies to the real deal and work the same way as container managed EntityManagers and ENtityManagerFactories.

Unfortunately when obtaining an EntityManager using

Object obj = ctx.lookup("java:managedEntityFactory." + unit);

@PersistenceContext
private EntityManager manager;

That's because "java:/managedEntityFactory...." is for INTERNAL USE ONLY!

The next release will provide a way to lookup ENtityManager, ENtityManagerFactory in global JNDI.