如何使用 JPQL 从 Spring 数据存储库获取 HashMap 结果？

Question

我目前已经在User 、 Shop和Role之间使用 Map 实现了三元关系。 所以在我的用户实体中我有这个映射：

用户.java

@Entity
@Table(name = "us_users")
public class User implements Serializable {

@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
@Column(nullable = false)
private int id;

@Basic(fetch = FetchType.LAZY, optional = false)
private String uuid;

@NotBlank(message = "First name can not be empty")
@Column(name = "usFname")
private String usFname;

@NotBlank(message = "Username can not be left empty")
@Column(name = "us_lname")
private String usLname;

@NotBlank(message = "Email field can not be empty")
@ValidEmail
    @Column(name = "usEmail", unique = true)
    @Basic(fetch = FetchType.LAZY, optional = false)
    private String usEmail;
 //this is the actual mapping
//a user can have a list of shops, but one role assigned for each shop
@ManyToMany
    @MapKeyJoinColumn(name = "shop_fk")
    @JoinTable(name = "user_shop_role",
            joinColumns = @JoinColumn(name = "user_fk"), inverseJoinColumns = @JoinColumn(name = "role_fk"))
    private Map<Shop, Role> shopRoleMap = new HashMap<>();
//GETTERS AND SETTERS,
}

角色.java

@Entity
@Table(name = "ro_roles")
public class Role {

@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
@Column(nullable = false)
private int id;

@Column(name = "rn_role_name")
private String roleName;

public int getId() {
    return id;
}

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

public String getRoleName() {
    return roleName;
}

public void setRoleName(String roleName) {
    this.roleName = roleName;
}

}

店铺.java

@Entity
@Table(name = "sh_shops")
public class Shop {
@Id
@GeneratedValue(strategy=GenerationType.IDENTITY)
@Column(nullable = false)
private int id;

@NotBlank(message = "Shop name can not be left blank")
private String sh_name;

@NotBlank(message = "please provide shop icon")
private String sh_icon;

@NotBlank(message = "please fill the shop description")
private String sh_description;

@NotBlank
private String sh_tag;
//setters, getters, equals, hashCode methods.
}

此映射为我提供了数据库中的另一个表 ( user_shop_role )，其中包含user_fk 、 shop_fk和role_fk ，这很可爱。 困难的一点是使用 Spring 数据 JPA 进行查询，并为给定用户获得 HashMap 的结果：登录用户的 HashMap<Shop,Role>。

在 UserRepository 层我试过这个：

接口UserRepository扩展了 JpaRepository 并且我有这个查询......

@Query("SELECT u FROM User u join shopRoleMap m where key(m)= usEmail")
     public HashMap<Shop, Role> findByUser(String email);


}

我如何获得使用 Map 集合映射的三元关系的结果，以获取商店列表和相应的角色值。 更多的关键，价值结果？

Answer 1

• 存储库方法。

    @Repository
    public interface UserRepository
            extends JpaRepository<User, Integer> {
    
        @Query("SELECT key(m), value(m) FROM User u join u.shopRoleMap m" +
                " where u.usEmail = :email")
        List<Object[]> findByUserEmail(String email);
    
    }

• 生成的查询。

    select
        shop3_.id as id1_1_0_,
        role2_.id as id1_0_1_,
        shop3_.sh_description as sh_descr2_1_0_,
        shop3_.sh_icon as sh_icon3_1_0_,
        shop3_.sh_name as sh_name4_1_0_,
        shop3_.sh_tag as sh_tag5_1_0_,
        role2_.rn_role_name as rn_role_2_0_1_ 
    from
        us_users user0_ 
    inner join
        user_shop_role shoprolema1_ 
            on user0_.id=shoprolema1_.user_fk 
    inner join
        ro_roles role2_ 
            on shoprolema1_.role_fk=role2_.id 
    inner join
        sh_shops shop3_ 
            on shoprolema1_.shop_fk=shop3_.id 
    where
        user0_.us_email=?

用上面的代码加上另一种方式更新

Github 回购 - https://github.com/kavi-kanap/stackoverflow-6313585

Answer 2

Spring 数据 JPA 具有称为属性表达式的功能，您可以在其中访问子实体或相关实体

例如

List<Shop> findByUser_email(String email);

有关更多详细信息，请参阅此

Spring 数据 JPA 文档

示例示例