Question

我有两个表（列）： PARENT（P_ID_PK，AUTO_INCREMENT）和儿童（P_ID_FK，C_NAME（PK = P_ID + C_NAME））

他们有一对多的关系。当我持久保存父对象和子对象时，P_ID_PK具有auto_incremented值，但P_ID_FK仅具有默认值（0）。如何让P_ID_FK具有与P_ID_PK相同的值？这是我的代码：

@Entity
@Tabler (name="PARENT")
public class Parent {
  @ID
  @Column (name = "P_ID_PK")
  @GeneratedValue(strategy=GenerationType.Identity)
  private Integer pIdPk;

  @OneToMany(mappedBy = "parent", cascade={CascadeType.ALL})
  @JoinColumn (name = "P_ID_PK")
  private List<Child> children;
  //...getters setters, constructors 
 }

@Embeddable
public class ChildId implements Serializable {
  private Integer pIdFk;
  private String cName;

  @Column(name="P_ID_FK")
  public Integer getPIdFk(){
  return this.pIdFk;}

  @Column(name="C_NAME")
  public String getCName(){
  return this.cName;}
  //... setters, @Override hashCode(),equals()
}

@Entity
@Table(name="CHILD")
public class Child {
  @EmbeddedId
  @AttributeOverrides({
     @AttributeOverride (name="pIdFk", column=@Column(name="P_ID_FK")),
     @AttributeOverride (name="cName", column=@Column(name="C_NAME"))})
 private ChildId childId;

@ManyToOne
@JoinColumn (name="P_ID_FK", referencedColumnName="P_ID_PK")
private Parent parent;
 //... Constructors, getters and setters 
}

test:
{
Session session = sessionFactory.openSession();
Transaction tx = session.beginTransaction();

Parent p = new Parent();
List<Child> cs = new Arraylist<Child>();
ChildId cId = new ChildId();
cId.setCName("xxx");
Child C = new Child();
c.setChildId(cId);
c.setParent(p);
cs.add(c);
p.setChildren(cs);

session.save(p);
System.out.println("pIdPk= "+p.getPIdPk());
System.out.println("pIdFk= "+p.getChidren().get(0).getPIdFk);
....
}

Output:
pIdPk= Auto_incremented values (works well)
pIdFk= 0 (Problem: how to have the same value as pIdPk?)

Answer 1

经过多次尝试，似乎无法自动填充作为复合键一部分的外键。我找到了两种解决方法：1）首先坚持父母，然后读取pk值，设置fk值并坚持孩子; 2）使用ElementCollection。

Hibernate在复合id中自动填充外键

1 个答案: