Question

我的WEB应用程序中存在CascateType.ALL的问题。更新我的实体Aluno后，我的子实体NivelAlunoLinguaEstrangeira无法按预期工作

@Entity
@Table(name = "ed44_aluno")
@SequenceGenerator(name = "ED44_SQC", sequenceName = "ed44_aluno_ed44_cod_aluno_seq", initialValue = 0, allocationSize = 1)
public class Aluno implements AbstractEntity {

    @Id
    @GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "ED44_SQC")
    @Column(name = "ed44_cod_aluno")
    private Long id;

    @OneToMany(mappedBy = "aluno", cascade = { CascadeType.ALL })
    private List<NivelAlunoLinguaEstrangeira> linguas;

}

@Entity
@Table(name = "ed77_linguagem_aluno")
@SequenceGenerator(name = "ED77_SQC", sequenceName = "s_ed77_linguagem_aluno", initialValue = 0, allocationSize = 1)
public class NivelAlunoLinguaEstrangeira implements AbstractEntity {

    @Id
    @GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "ED77_SQC")
    @Column(name = "ed77_cod_linguagem")
    private Long id;

    @OneToOne
    @JoinColumn(name = "fked77ed44_cod_aluno")
    private Aluno aluno;

}

    public static void main(String[] args) {
        EntityManagerFactory factory = Persistence.createEntityManagerFactory("post");      
        EntityManager manager = factory.createEntityManager();
        Aluno aluno = manager.find(Aluno.class, 1l);
        aluno.getLinguas().size();
        manager.close();

        NivelAlunoLinguaEstrangeira nivel = new NivelAlunoLinguaEstrangeira();
        nivel.setAluno(aluno);
        aluno.addLingua(nivel);

        manager = factory.createEntityManager();
        manager.getTransaction().begin();
        manager.merge(aluno); //update
        manager.getTransaction().commit();
        manager.close();

        System.out.println(nivel); // nivel.getId() == null WHY?
    }

我的输出：

找到方法调用后

：

选择aluno，其中id = 1（已编辑，长查询）

合并方法调用后：

选择nextval（'s_ed77_linguagem_aluno'）

提交后

：

插入ed77_linguagem_aluno（fked77ed44_cod_aluno，fked77tg22_cod_nivel_lingua_ent，fked77tg22_cod_nivel_lingua_esc，fked77tg22_cod_nivel_lingua_fal，fked77tg22_cod_nivel_lingua_le，fked77tg33_cod_lingua，ed77_cod_linguagem）的值（？，？，？，？，？，？，？）

代码结束：

NivelAlunoLinguaEstrangeira [id = null，aluno = Aluno [id = 1，codigoInep = null，codigoNis = null，nome = FULANO DE TAL EDITADO 8，apelido = null，nascimento = null，nDependentes = null，mae = null，pai = null，conjuge = null，fotoSrc = null，dataCadastro = 2014-05-23 15：46：43.586，endereco = null，contato = null，documentacao = null]，lingua = null，escreve = null，entende = null，fala = null，leitura = null]

问题是：为什么我的实体NivelAlunoLinguaEstrangeira没有收到您的身份证明？

Answer 1

由于merge会返回修改后的值，因此无法按照文档here触及参数。

所以你需要像这样保留引用：

manager = factory.createEntityManager();
manager.getTransaction().begin();
aluno = manager.merge(aluno); //update
manager.getTransaction().commit();
manager.close();

父实体合并后，实体的子节点不会收到id

1 个答案: