public void create(Usuarios usuarios) throws PreexistingEntityException, RollbackFailureException, Exception {
        EntityManager em = null;
        try {
            utx.begin();
            em = getEntityManager();
            em.persist(usuarios);
            utx.commit();
        } catch (Exception ex) {
            try {
                utx.rollback();
            } catch (Exception re) {
                throw new RollbackFailureException("An error occurred attempting to roll back the transaction.", re);
            }
            if (findUsuarios(usuarios.getNoIfe()) != null) {
                throw new PreexistingEntityException("Usuarios " + usuarios + " already exists.", ex);
            }
            throw ex;
        } finally {
            if (em != null) {
                em.close();
            }
        }
    }