Question

我有2个分类用户和底部，用户与Bottom有很多关系。用户有2个复合键

用户id

class TireId {
 private String uId;
 private String schoolId
}

用户实体：

@IdClass(UserId.class)
@Entity
Class User {

 @Id
 private String uId;
 @Id
 private String schoolId

    @OneToMany(mappedBy="user")
    private List<Bottom> bottoms;


}

BottomId：

class BottomId {
   private String bId;
   private String cId;
   private String schoolId;

}

底层课程：

@IdClass(BottomId.class) 
@Entity
class Bottom {
    private String bId;
   private String cId;
   private String schoolId;
    @ManyToOne
   private  User user;
}

在上面的例子中，hibernate将在底部表名user_uId和user_schoolId中创建2个附加列。

但我需要User with OneToMany与以下关系的关系

schoolId of user == schoolId of Bottom
and uId of user == cId of of Bottom

我如何存档？

Answer 1

这是“派生身份”，因此BottomId应如下所示：

class BottomId {
    private String bId;
    private UserId user; // matches name of attribute and type of User PK
}

和Bottom应该像这样映射：

@IdClass(BottomId.class) 
@Entity
class Bottom {
    @Id
    private String bId;

    @Id
    @JoinColumns({
        @JoinColumn(name="cId", referencedColumnName="uId"),
        @JoinColumn(name="schoolId", referencedColumnName="schoolId")
    })
    @ManyToOne
    private  User user;
}

在第2.4.1节的JPA 2.1规范中讨论了衍生身份（带有示例）。

具有复合键的OneToMany

1 个答案: