java - hibernate/JPA : Is it possible to Override @Id field?

Question

@Id 分配给父实体中的某个字段后，是否有方法重新分配子实体中的 @Id

例如:

@MappedSuperclass
@Access(AccessType.FIELD)
public abstract class Parent implements Serializable {

  @Id
  protected Integer parentId;

  public Integer getId() {
    return parentId;
  }

  public void setId(Integer id) {
    this.id = parentId;
  }
}


@Entity
@Access(AccessType.FIELD)
public class Child extends Parent implements Serializable {

  /*
   What should be added to this entity to re assign the @Id to a new field and 
   make the parentId field just an ordianry field in the Child, not the entity Id
  */
  @Id
  private Long childId;

}

我试过使用@AttributeOverride , 但它所能提供的只是重命名 id 列名称。

Answer 1

这听起来像是一个设计问题。

实现这一目标的正确方法可能是定义另一个类:@MappedSuperclass GenericEntity 具有 Parent 除了 parentId 的所有属性:

@MappedSuperclass
@Access(AccessType.FIELD)
public abstract class GenericEntity implements Serializable {
     ... all your common attributes without parentId
}

@MappedSuperclass
public abstract class Parent extends GenericEntity implements Serializable {

    @Id
    protected Integer parentId;

    public Integer getId() {
        return parentId;
    }

    public void setId(Integer id) {
        this.id = parentId;
    }

    //nothing more in this class
}

@Entity
public class Child extends GenericEntity implements Serializable {

   @Id
   private Long childId;

   private Integer parentId; //if you need it

   ...
}    

---

另一种实验性解决方案是隐藏 Child 类中的 parentId 字段。

免责声明:我不推荐这种方法，我不确定它是否有效!

@Entity
@Access(AccessType.FIELD)
public class Child extends GenericEntity implements Serializable {

   @Id
   private Long childId;

   private Integer parentId;

   ...
}