There are several ways to use an EntityManagerFactory. One is indeed Persistence.createEntityManagerFactory but you need to set the ContextClassLoader to a classloader that can see the persistence provider as well as the database drivers. This is more a workaround than a good solution.
Another option is to use Aries JPA. It creates the EMF from you persistence.xml and offers it as an OSGi service which you can then refer to. See https://github.com/apache/aries-jpa/tree/master/examples Christian
