小编Sim*_*0rn的帖子

我有一个关于从Child Entites引用ParentEntities的问题如果我有这样的事情:

Parent.java:

@Entity(name ="Parent")
public class Parent {
    @Id
    @Generate.....
    @Column
    private int id;

    @OneToMany(cascade = CascadeType.ALL, fetch = FetchType.LAZY, mappedBy = "parent")
    private Set<Child> children;

    simple ... getter and setter ...
}

而Child.java:

@Entity(name ="Child")
public class Child{
    @Id
    @Generate....
    @Column
    private int id;

    @ManyToOne
    private Parent parent;

    ... simple getter an setter
}

将创建以下表:

Parent:
     int id

Child:
     int id
     int parent_id (foreign key: parent.id)

好吧,到目前为止,everthings很好.但是当谈到从Java使用这个参考时,我想,你可以做这样的事情.

 @Transactional
 public void test() {
    Parent parent = new Parent();

    Child …