Mybatis嵌套查询结果集中包含简单数据类型集合或者多个List的处理

1. 包含多个 List(String)属性的情况

数据库数据

mysql> select * from ai_user;
+----+-----------+--------+
| id | user_name | status |
+----+-----------+--------+
|  1 | Answer    |      1 |
|  2 | Iris      |      1 |
+----+-----------+--------+

mysql> select * from ai_name;
+---------+-----------+
| user_id | user_name |
+---------+-----------+
|       1 | Answer    |
|       1 | AI        |
|       1 | AAL       |
|       2 | Iris      |
|       2 | Ellis     |
|       2 | Monta     |
+---------+-----------+

mysql> select * from ai_role;
+---------+-----------------+
| user_id | role_name       |
+---------+-----------------+
|       1 | Admin           |
|       1 | Manager         |
|       1 | Coder           |
|       2 | CustomerService |
+---------+-----------------+

实体类

@Data
public class User {
    private Long id;
    private List<String> names;
    private List<String> roles;
}

Mapper 层

public interface UserMapper {
    List<User> queryUsers();
}

Mapper Sql 映射文件

<resultMap id="UserMap" type="User">
   <result column="id" property="id" jdbcType="BIGINT" />
    <collection property="names" resultMap="NamesMap" />
    <collection property="roles" resultMap="RolesMap" />
</resultMap>

<resultMap id="NamesMap" type="string">
    <result column="user_name" />
</resultMap>

<resultMap id="RolesMap" type="string">
    <result column="role_name" />
</resultMap>

<select id="queryUsers" resultMap="UserMap">
	SELECT au.id, an.user_name, ar.role_name
    FROM ai_user au
    LEFT JOIN ai_name an ON an.user_id = au.id
    LEFT JOIN ai_role ar ON ar.user_id = au.id
</select>

结果输出示例

{"id":1,"names":["Answer","AI","AAL"],"roles":["Admin","Manager","Coder"]}
{"id":2,"names":["Iris","Ellis","Monta"],"roles":["CustomerService"]}

2. 包含多个 List(T) 和 List(String)属性的情况

实体类

@Data
public class SysUser {
    private Long id;

    private String loginName;

    private String userName;

    private String email;

    private List<Long> roleIds;

    private List<SysRole> roles;
}

@Data
public class SysRole {
    private Long id;

    private String roleName;

    private String roleDesc;
}

Mapper 接口

public interface UserMapper {
    List<SysUser> findUsers(int status);
}    

Mapper Sql 映射文件

<resultMap id="SysUserMap" type="com.answer.ai.entity.SysUser">
    <id column="id" property="id" jdbcType="BIGINT" />
    <result column="login_name" property="loginName" jdbcType="VARCHAR"/>
    <result column="user_name" property="userName" jdbcType="VARCHAR"/>
    <result column="email" property="email" jdbcType="VARCHAR"/>
	
	<!-- userId 和 roleStatus 为查询 findRoleById 的入参, id 和 role_status 为查询 findUsers 的结果信息 -->
	<!-- 如果查询 findRoleById 需要 roleId 作为入参, column 写法 {userId=id,roleStatus=role_status,roleId=role_id} -->
    <collection property="roles" ofType="com.answer.ai.entity.SysRole" select="findRoleById" column="{userId=id,roleStatus=role_status}" />
    <collection property="roleIds" ofType="Long">
        <constructor>
            <arg column="role_id" />
        </constructor>
    </collection>
</resultMap>

<!-- 查询 findUsers 的入参 #{status} 放在结果集上作为查询 findRoleById 作为入参 -->
<select id="findUsers" parameterType="Integer" resultMap="SysUserMap">
    SELECT su.id, su.login_name, su.user_name, su.email, sur.role_id, #{status} AS role_status
    FROM ai_user su
    LEFT JOIN dc_sys_user_role sur ON sur.user_id = su.id
</select>


<select id="findRoleById" resultType="com.answer.ai.entity.SysRole">
    SELECT id, role_name, role_descript AS role_desc
    FROM ai_user_role
    WHERE user_id = #{userId} AND role_status = #{roleStatus}
</select>

接口调用结果

{
    "code": 10000,
    "desc": "success",
    "data": [
        {
            "id": 1,
            "loginName": "admin",
            "userName": "林**",
            "email": "[email protected]",
            "roleIds": [
                1
            ],
            "roles": [
                {
                    "id": 1,
                    "roleName": "admin",
                    "roleDesc": "超级管理员"
                }
            ]
        },
        {
            "id": 2,
            "loginName": "answer",
            "userName": "杨**",
            "email": "[email protected]",
            "roleIds": [
                2,
                3
            ],
            "roles": [
                {
                    "id": 2,
                    "roleName": "answer",
                    "roleDesc": "普通管理员"
                },
                {
                    "id": 3,
                    "roleName": "develop",
                    "roleDesc": "开发者权限"
                }
            ]
        }
    ]
}

Refer

https://blog.csdn.net/u010979642/article/details/100668909
https://blog.csdn.net/u010979642/article/details/94646861?depth_1-utm_source=distribute.pc_relevant.none-task-blog-BlogCommendFromBaidu-2&utm_source=distribute.pc_relevant.none-task-blog-BlogCommendFromBaidu-2