Question

@Data
@Entity
@Table(name = "member")
public class MemberEntity {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Integer id;

    @OneToMany
    @JoinColumn(name = "memberId")
    private List<PhoneEntity> phoneEntities;
}


@Data
@Entity
@Table(name = "phone")
public class PhoneEntity {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Integer id;

    @Column
    private Integer memberId;
}


@Repository
public interface MemberRepository extends JpaRepository<MemberEntity, Integer> {

    @Query("select m from MemberEntity m join fetch m.phoneEntities where m.id=?1")
    MemberEntity findByIdWithPhone(Integer id);
}

创建从Member到Phone的OneToMany关系

im试图使用Member查询选择Phone与@Query("select m from MemberEntity m join fetch m.phoneEntities where m.id=?1")提取联接

此查询的创建方式类似于在my-sql查询下

SELECT 
memberenti0_.id as id1_0_0_,
phoneentit1_.id as id1_1_1_,
phoneentit1_.member_id as member_i2_1_1_,
phoneentit1_.member_id as member_i2_1_0__,
phoneentit1_.id as id1_1_0__ 
from member memberenti0_
inner join phone phoneentit1_ on memberenti0_.id=phoneentit1_.member_id
where memberenti0_.id=?

并且结果MemberEntity不为空（这意味着插入和内部联接有效！），但MemberEntity#phoneEntities始终为空

我试图更改List<PhoneEntity> Collections<PhoneEntity> Set<PhoneEntity>的所有集合类型无效。

我怀疑在生成的查询中，“电话”表中的列调用两次（member_i2_1_1_，member_i2_1_0__），但我不知道为什么。

Answer 1

您必须将映射更正为：

@Data
@Entity
@Table(name = "member")
public class MemberEntity {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Integer id;

    @OneToMany(
        mappedBy = "member"
    )        
    private List<PhoneEntity> phoneEntities;
}


@Data
@Entity
@Table(name = "phone")
public class PhoneEntity {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Integer id;

    @ManyToOne(fetch = FetchType.LAZY) // Or Eager 
    @JoinColumn(name = "member_id")
    private MemberEntity member;
}

并且无需在查询中指定连接：

@Query("select m from MemberEntity m where m.id=?1")

Spring JPA @OneToMany一个方向始终为null

1 个答案: