Hibernate Cascade PERSIST

问题

I have a general question about Hibernate that I'm batteling with.

I have class A and class B, where B is dependent on A

In my code when I call em.persist(objOfTypeA) I would expect the insert to go and insert into both tables AAA and BBB. If I manually presist A get A's ID and fill it in the list for each object and then persist that list, things are working. But I would expect this to happen magically by Hibernate.

Am I doing something wrong? Or am I just expecting too much of Hibernate?

Thanks

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

    @Id
    @GeneratedValue
    @Column(name = "Id")
    private Long id;


    @NotNull
    @Column(name = "Name")
    private Long name;

    ...

    @OneToMany(mappedBy="a", fetch=FetchType.LAZY, cascade={CascadeType.PERSIST, CascadeType.MERGE, CascadeType.REMOVE})
    private List<B> b;
...
}

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

    @Id
    @GeneratedValue
    @Column(name="Id")
    private Long id;

    @NotNull
    @Column(name="AId")
    private Long aId;

    @NotNull
    @Column(name = "Name")
    private Long name;

    @JoinColumn(name = "AId", referencedColumnName="Id", updatable = false, insertable = false)
    @ManyToOne(optional = false)
    private A a;
...     
}

回答1:

I finally worked it out. None of the examples I was given or found told me exactly what was wrong, it was only after my own experimentation that I managed to come to this conclusion:

Instead of having

@OneToMany(mappedBy="a", fetch=FetchType.LAZY, cascade={CascadeType.PERSIST, CascadeType.MERGE, CascadeType.REMOVE})
private List<B> b;

that didn't work (FK was still coming as NULL)

This did work:

@OneToMany(fetch=FetchType.LAZY, cascade={CascadeType.PERSIST, CascadeType.MERGE, CascadeType.REMOVE})
@JoinColumn(name="AId")
@NotNull
private List<B> b;

回答2:

Modify the mapping of class B as below,

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

    @Id
    @GeneratedValue
    @Column(name="Id")
    private Long id;

    @NotNull
    @Column(name="AId", updatable = false, insertable = false)
    private Long aId;

    @NotNull
    @Column(name = "Name")
    private Long name;

    @JoinColumn(name = "AId", referencedColumnName="Id")
    @ManyToOne(optional = false)
    private A a;
...     
}

You were using the attributes updatable = false, insertable = false at wrong place and I have corrected it.

Read here to understand how they works.

来源：https://stackoverflow.com/questions/9443540/hibernate-cascade-persist

标签

hibernate

jpa

Cascade

persist