Question

我有3个表A，B和映射表A_B，其中包含两者的ID（A_ID和B_ID）。以下是映射这3个表的java类的外观：

@Entity
@Table(name = "A")
public class A {

    @Id
    @GeneratedValue(strategy = GenerationType.SEQUENCE)
    @Column(name = "ID")
    private Long id;

    @OneToMany(cascade=CascadeType.ALL)
    @JoinColumn(name = "FK_A", referencedColumnName="Id", nullable = false)
    private Set<A_B> ab;

    //Other attributes, Getters Setters etc.
}

@Entity
@Table(name = "A_B")
public class A_B {

     @Id
     @GeneratedValue(strategy = GenerationType.SEQUENCE)
     @Column(name = "ID")
     private Long id;

     @ManyToOne(cascade=CascadeType.ALL)
     @JoinColumn(name = "FK_B", nullable = false)
     private B b;

     //Other attributes, Getters Setters etc.
 }

Entity
@Table(name = "B")
public class B  {

    @Id
    @GeneratedValue(strategy = GenerationType.SEQUENCE)
    @Column(name = "ID")
    private Long id;

    //Other attributes, Getters Setters etc.
}

现在让我说我已经坚持了B（b）的对象。现在我想要坚持A（a）的对象和这两者之间的关联（ab）。我的代码如下：

@PersistenceContext(unitName = "demoPU")
private EntityManager em;

B b = em.createNamedQuery(queryName, B); // Getting obj of B
A a = new A();
A_B ab = new A_B();
ab.setB(b); // Setting B in relationship
a.setAb(ab);

em.persist(a);

然而，这又试图坚持b＆amp;由于它的id已经设置，因此抛出异常：

org.hibernate.PersistentObjectException: detached entity passed to persist

您是否可以告诉我如何在不必再次坚持B的情况下坚持这种情况下的关联？

Answer 1

为什么不尝试设置a而不是b？

你也可以在一个空格中清空它，所以它不会试图坚持它。

编辑：正如评论中所述，它没有预期的效果。您应该使用saveOrUpdate()

中建议的persist()代替

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var o = new JavaAdapter(javax.net.ssl.X509TrustManager, obj);
var oo = new Array();
oo.push(o);

Hibernate持久映射

1 个答案: