Designing a Session‑Based Scene API with MyBatis: Entities, Mapper, Service, and Controller

1. Business Background

In the business scenario a single session_id can correspond to multiple scene_id and scene_name values.

To avoid repeating the same sessionId in every object, the author proposes moving the session identifier to the outer level.

2. Entity Classes

Two Java POJOs are defined: SceneVO containing a sessionId and a List<SubSceneVO> sceneList , and SubSceneVO holding sceneId and sceneName .

public class SceneVO {
    private String sessionId;
    private List
sceneList;
    // getters and setters omitted
}

public class SubSceneVO {
    private String sceneId;
    private String sceneName;
    // getters and setters omitted
}

3. Custom Mapper and XML

The MyBatis mapper interface declares a method to fetch a SceneVO by sessionId :

public interface BusinessScenesCustomMapper {
    SceneVO selectBySessionId(String sessionId);
}

The accompanying XML maps the session_id column to sessionId and uses a <collection> element to populate sceneList from the scene_id and scene_name columns:

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="your.package.mapper.BusinessScenesCustomMapper">
    <resultMap id="BaseResultMap" type="your.package.vo.SceneVO">
        <result column="session_id" property="sessionId" jdbcType="VARCHAR"/>
        <collection property="sceneList" ofType="your.package.vo.SubSceneVO">
            <result column="scene_id" property="sceneId" jdbcType="VARCHAR"/>
            <result column="scene_name" property="sceneName" jdbcType="VARCHAR"/>
        </collection>
    </resultMap>
    <select id="selectBySessionId" parameterType="string" resultMap="BaseResultMap">
        SELECT session_id, scene_id, scene_name FROM your_table WHERE session_id = #{sessionId,jdbcType=VARCHAR}
    </select>
</mapper>

4. Service Layer

An interface defines the business method and its implementation injects the mapper:

public interface SceneService {
    /** Get scene information */
    SceneVO getScenesInfo(String sessionId);
}

@Service
public class SceneServiceImpl implements SceneService {
    @Resource
    private BusinessScenesCustomMapper businessScenesCustomMapper;

    @Override
    public SceneVO getScenesInfo(String sessionId) {
        return businessScenesCustomMapper.selectBySessionId(sessionId);
    }
}

5. Controller Layer

A Spring MVC controller exposes the service through a GET endpoint and wraps the result in a generic response model:

@RestController
public class SceneController {
    @Resource
    private SceneService sceneService;

    @GetMapping("/getScenesInfo")
    public ResModel getScenesInfo(String sessionId) {
        SceneVO sceneVO = sceneService.getScenesInfo(sessionId);
        return ResModel.ok(sceneVO);
    }
}