QueryDSL fetchJoin不提取数据

Question

long id

String someField

// No bidirectional linkage to B entity via hibernate

long id

String someBField

@ManyToOne(optional = false, fetch = FetchType.LAZY)
@JoinColumn(name="b_id")
A entityA

@ManyToOne(optional = true, fetch = FetchType.LAZY)
@JoinColumn(name="b_id")
C entityC;   

实体C：

long id

String someCField

// No bidirectional linkage to B entity via hibernate

现在，目标是（为了简单起见，有一些排序和过滤，但这不影响我的问题）返回所有B记录，每个记录都带有A和C记录

所以我正在做这样的事情（我习惯于使用spring-data-jpa来(LEFT)JOIN FETCH属性，以避免按需惰性加载，防止向数据库触发无用的查询，我想在QueryDSL中做完全相同的事情）

    JPAQuery<DealBo> query = new JPAQuery<>(entityManager);

    query.select(qB)
            .from(qB)
            .innerJoin(qA).on(qA.a_id.eq(qB.id)).fetchJoin()
            .innerJoin(qC).on(qC.a_id.eq(qB.id)).fetchJoin()
            .fetch()

select b.id, b.someBfield from b
inner join a // join clause is right and omitted for simplicity
inner join b // join clause is right and omitted for simplicity

b.getc（）或b.geta()，我正在向数据库触发另一个查询，这是我首先要避免的事情。

我做错了什么？

Answer 1

我认为，连接条件的定义是不恰当的。

希望我已经用UserEntity<-UserRoleEntity->roleentity重新创建了所描述的星座：

@Entity
@Table(name = "t_user")
public class UserEntity {

    @Id
    @Column(name = "id")
    private Integer id;
    @Column(name = "name") 

    // ..
}

@Entity
@Table(name = "t_user_role")
public class UserRoleEntity {
    @Id
    @Column(name = "id")
    private Integer id;
    @ManyToOne
    @JoinColumn(name = "user_id")
    private UserEntity user;
    @ManyToOne
    @JoinColumn(name = "role_id")
    private RoleEntity role;

    // ..
}

@Entity
@Table(name = "t_role")
public class RoleEntity {
    @Id
    @Column(name = "id")
    private Integer id;
    @Column(name = "name")
    private String name;

    // ..
}

查询

List<UserRoleEntity> findAll() {
    JPAQuery<UserRoleEntity> query = new JPAQuery<>(entityManager);

    return query.select(QUserRoleEntity.userRoleEntity)
            .from(QUserRoleEntity.userRoleEntity)
            .innerJoin(QUserRoleEntity.userRoleEntity.user).fetchJoin()
            .innerJoin(QUserRoleEntity.userRoleEntity.role).fetchJoin()
            .fetch();

}

    select 
        userroleen0_.id as id1_5_0_, 
        userentity1_.id as id1_4_1_, 
        roleentity2_.id as id1_2_2_, 
        userroleen0_.role_id as role_id2_5_0_, 
        userroleen0_.user_id as user_id3_5_0_, 
        userentity1_.name as name2_4_1_, 
        roleentity2_.name as name2_2_2_ 
    from t_user_role userroleen0_ 
    inner join t_user userentity1_ on userroleen0_.user_id=userentity1_.id 
    inner join t_role roleentity2_ on userroleen0_.role_id=roleentity2_.id