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<SceneVO>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" } ] } }
Java 集合系列文章：https://www.javastack.cn/categories/Java/
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sceneList ofType：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_name from 表名 where session_id = #{sessionId,jdbcType=VARCHAR} </select> </mapper>
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 { @Resource private 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); }
