public class Application {
      
       @Resource
       private UserTransaction utx = null;
       
       // Initialized on each application request and not closed!
       @PersistenceUnit(unitName = "UnitName")
       private EntityManagerFactory emf = Persistence.createEntityManagerFactory("PersistenceUnit"); 

       public EntityManager getEntityManager() {
             return this.emf.createEntityManager();
       }
      
       public void businessMethod() {
            
             // Create a new EntityManager instance via from the newly created EntityManagerFactory instance
             // Do something...
             // Close the EntityManager instance
       }
}