我正在嘗試使用 eclipselink + @ejb 注釋 DAO 提供的 JPA 來持久化一個(gè)對(duì)象。但是當(dāng)我單擊查看命令按鈕時(shí)，它無法持續(xù)存在。已經(jīng)嘗試使用一些互聯(lián)網(wǎng)簡(jiǎn)單的示例代碼，同樣的錯(cuò)誤。道：@Statelesspublic class ClienteDAO {    @PersistenceContext(unitName = "br.com.lucas_app_war_1.0-SNAPSHOTPU")    private EntityManager em;    public void save(Cliente cliente) {        em.persist(cliente);    }}實(shí)體：@Entitypublic class Cliente implements Serializable {    @Id    @SequenceGenerator(name = "seq_cliente", allocationSize = 1,sequenceName = "seq_cliente")    @GeneratedValue(generator = "seq_cliente", strategy = GenerationType.SEQUENCE)    private long id;    private String nome;    private String cpf;   //getters and setters    }托管豆：@ManagedBean(name = "ClienteMB")@ViewScopedpublic class ClienteManagedBean implements Serializable {    @EJB    private ClienteDAO dao;    private Cliente cliente;    private List<Cliente> clientes;    @PostConstruct    public void iniciar(){    cliente = new Cliente();    clientes = new ArrayList<>();    }    public void adicionar() {        dao.save(cliente);        clientes.add(cliente);        cliente = new Cliente();    }    //getters and setters}