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1.业务背景

业务场景中，一个会话中存在多个场景，即一个session_id对应多个scene_id和scene_name

如果你写成如下的聚合模型类

public class SceneVO {private String sessionId;private String sceneId;private String sceneName;// 省略对应的getter和setter方法
}

返回的List形式如下，这个数据在data属性中

{"data":[{"sessionId": "jksadhjksd","sceneId":"NDJWKSDSJKDKED","sceneName":"场景1"},{"sessionId": "jksadhjksd","sceneId":"KLJSDJKLSDFALK","sceneName":"场景2"},{"sessionId": "jksadhjksd","sceneId":"KERFJKOVDJKDSS","sceneName":"场景3"}]
}

每个对象里面都带上了重复的一个sessionId数据，我想提出来该怎么办？

我想改为如下形式，sessionId提出到外层，更能体现出一个sessionId对应多个sceneId和sceneName的含义，这样也便于前端取数据，不然每个对象都要增加一个sessionId属性，太麻烦。

{"data": {"sessionId": "jksadhjksd","sceneList": [{"sceneId":"NDJWKSDSJKDKED","sceneName":"场景1"},{"sceneId":"KLJSDJKLSDFALK","sceneName":"场景2"},{"sceneId":"KERFJKOVDJKDSS","sceneName":"场景3"}]}
}

2.实体类

方法如下，首先创建两个实体类。

public class SceneVO {private String sessionId;private List<SubSceneVO> sceneList;// 省略对应的getter和setter方法
}
public class SubSceneVO {private String sceneId;private String sceneName;// 省略对应的getter和setter方法
}

3.自定义Mapper和xml文件

public interface BusinessScenesCustomMapper {SceneVO selectBySessionId(String sessionId);
}
<?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="你的包名.mapper.BusinessScenesCustomMapper"><resultMap id="BaseResultMap" type="你的包名.vo.SceneVO"><result column="session_id" jdbcType="VARCHAR" property="sessionId"/><!--collection 标签：用于定义关联的list集合类型的封装规则property：对应父类中list属性名，这里SceneVO类里的List变量名为sceneListofType：集合存放的类型，List集合要装的类的类名，这里是SubSceneVO--><collection property="sceneList" ofType="你的包名.vo.SubSceneVO"><result column="scene_id" jdbcType="VARCHAR" property="sceneId"/><result column="scene_name" jdbcType="VARCHAR" property="sceneName"/></collection></resultMap><!-- 一个session_id对应多条记录，返回的是SceneVO对象，SceneVO对象有一个List装着SubSceneVO  --><select id="selectBySessionId" parameterType="string" resultMap="BaseResultMap">select session_id, scene_id, scene_namefrom 表名where session_id = #{sessionId,jdbcType=VARCHAR}</select>

• collection标签： 用于定义关联的List集合类型的封装规则
• property属性： 对应父类中List集合的变量名，这里SceneVO类里的List变量名为sceneList
• ofType属性： 集合存放的类型，List集合要装的类的类名，这里是SubSceneVO

4.Service层

public interface SceneService {/*** 获取场景信息*/SceneVO getScenesInfo(String sessionId);
}
@Service
public class SceneServiceImpl {@Resourceprivate BusinessScenesCustomMapper businessScenesCustomMapper;......public SceneVO getScenesInfo(String sessionId) {return businessScenesCustomMapper.selectBySessionId(sessionId);}
}

5.Controller层

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