Persistence.createEntityManagerFactory() in Java EE ignores JTA source - jpa

Question

I have a perfectly working application client deployed to a GlassFish v2 server inside an ear with some EJBs, Entities, etc. I'm using eclipselink.
Currently I have in my persistence.xml:
<persistence-unit name="mysource">
<provider>org.eclipse.persistence.jpa.PersistenceProvider</provider>
<jta-data-source>jdbc/mysource</jta-data-source>
<class>entities.one</class>
<class>entities.two</class>
...
<properties>
<property name="eclipselink.target-server" value="SunAS9"/>
<property name="eclipselink.logging.level" value="FINE"/>
</properties>
</persistence-unit>
And this works fine when I inject the EntityManager into the EJB:
#PersistenceContext(unitName="mysource")
private EntityManager em;
Now I have a requirement to dynamically switch persistence units/databases.
I figure I can get an EntityManager programatically:
em = Persistence.createEntityManagerFactory("mysource").createEntityManager();
but I get the following error:
Unable to acquire a connection from driver [null], user [null] and URL [null]
Even "overriding" javax.persistence.jtaDataSource" to "jdbc/mysource" in a Map and calling createEntityManagerFactory("mysource", map) doesn't make a difference.
What am I missing?

Answer 1

You are trying to circumvent the container with creating an entity manager programmatically and this means you'll most probably create a non-JTA data source (as it's outside the container, the transaction type should be RESOURCE_LOCAL), thus your original config is useless.
Try injecting an entity manager with a different unitName property or create a RESOURCE_LOCAL transaction type persistence unit.