code: private Connection createConnection() {
          try {
              EntityTransaction tx = this.em.getTransaction();
              if (isHibernatePresentOnClasspath() && em.getDelegate() instanceof Session) {
                  connection = ((SessionImpl) em.unwrap(Session.class)).connection();
              } else {
                  /**
                   * see here:http://wiki.eclipse.org/EclipseLink/Examples/JPA/EMAPI#Getting_a_JDBC_Connection_from_an_EntityManager
                   */
                  tx.begin();
                  connection = em.unwrap(Connection.class);
                  tx.commit();
              }
          } catch (Exception e) {
              throw new RuntimeException("Could not create database connection", e);
          }
  
          return connection;
      }
docs: unfortunately there is no standard way to get jdbc connection from JPA entity manager
  
  @return JDBC connection