code: protected EntityManagerFactory getEntityManagerFactory(OpenEntityManager openEntityManager) {
          final CacheKey key = this.createEntityManagerFactoryKey(openEntityManager);
          EntityManagerFactory emf = this.entityManagerFactories.get(key);
          if (emf == null) {
              emf = this.lookupEntityManagerFactory(openEntityManager);
              this.entityManagerFactories.put(key, emf);
          }
          return emf;
      }
docs: Get the EntityManagerFactory that this filter should use.
  
  @return the EntityManagerFactory to use
  @see #lookupEntityManagerFactory(OpenEntityManager)