mybatis返回jsonobject数据结果是空，怎么解决

mybatis返回jsonobject数据结果是空，怎么解决
准备不通过自己事先编写的类进行查询，如果有其他解决办法也可以

返回值[][]
数据库代码

public List<JSONObject> tableshow(String i) throws IOException {
        //创建SqlSessionFactory，会在src根路径下获取List<Emp>
        InputStream is = Resources.getResourceAsStream("mybatis.xml");
        SqlSessionFactory factory = new SqlSessionFactoryBuilder().build(is);
        //创建SqlSession  List<Emp>  (String l)List<String> //mm  List<Biaodan>
        SqlSession session = factory.openSession(true);
        i="SELECT * FROM "+i;//i是表名
       List<JSONObject> st1 = session.selectList("mapper.EmpMapper.tableshow",i);
       JSON.toJSONString(st1);
       System.out.print(JSON.toJSONString(st1));
       session.commit();
       return st1;
       }
mapper配置
 <select id="tableshow" resultType="com.alibaba.fastjson.JSONObject">
     ${i};
<!--获取表结构DESC logisticsroute;show columns from logisticsroute;更改表名: 命令：rename table 原表名 to 新表名rename table myclass2 to myclass4-->
    </select>

查询的结果和返回的类型不对应。

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• 你可以参考下这个问题的回答, 看看是否对你有帮助, 链接: https://ask.csdn.net/questions/227078
• 除此之外, 这篇博客: Mybatis使用中的 使用json显示返回的复合结构的对象 部分也许能够解决你的问题, 你可以仔细阅读以下内容或者直接跳转源博客中阅读:
  

  校验

  https://www.sojson.com/

  解析

  https://www.sojson.com/simple_json.html

   List<PlaceVo> list = placesMapper.getTree("昭通市");
          ObjectMapper objectMapper=new ObjectMapper();
          try {
              String json=objectMapper.writeValueAsString(list);
              System.out.println(json);
          } catch (JsonProcessingException e) {
              e.printStackTrace();
          }
  

  以上的结果：

  [{"id":"微信县","pid":"昭通市","distance":0,"size":"20","peopleNum":30,"placesList":[]},{"id":"盐津县","pid":"昭通市","distance":0,"size":"10","peopleNum":100,"placesList":[{"id":"串丝","pid":"盐津县","distance":110,"size":"1","peopleNum":20,"placesList":[]},{"id":"普洱镇","pid":"盐津县","distance":100,"size":"1","peopleNum":30,"placesList":[]}]},{"id":"绥江县","pid":"昭通市","distance":0,"size":"20","peopleNum":30,"placesList":[]},{"id":"镇雄县","pid":"昭通市","distance":0,"size":"10","peopleNum":300,"placesList":[{"id":"簸箕","pid":"镇雄县","distance":200,"size":"2","peopleNum":50,"placesList":[]},{"id":"罗坎","pid":"镇雄县","distance":113,"size":"5","peopleNum":40,"placesList":[]}]}]
  
  

  在线工具解析后：

  [{
  	"id": "微信县",
  	"pid": "昭通市",
  	"distance": 0,
  	"size": "20",
  	"peopleNum": 30,
  	"placesList": []
  }, {
  	"id": "盐津县",
  	"pid": "昭通市",
  	"distance": 0,
  	"size": "10",
  	"peopleNum": 100,
  	"placesList": [{
  		"id": "串丝",
  		"pid": "盐津县",
  		"distance": 110,
  		"size": "1",
  		"peopleNum": 20,
  		"placesList": []
  	}, {
  		"id": "普洱镇",
  		"pid": "盐津县",
  		"distance": 100,
  		"size": "1",
  		"peopleNum": 30,
  		"placesList": []
  	}]
  }, {
  	"id": "绥江县",
  	"pid": "昭通市",
  	"distance": 0,
  	"size": "20",
  	"peopleNum": 30,
  	"placesList": []
  }, {
  	"id": "镇雄县",
  	"pid": "昭通市",
  	"distance": 0,
  	"size": "10",
  	"peopleNum": 300,
  	"placesList": [{
  		"id": "簸箕",
  		"pid": "镇雄县",
  		"distance": 200,
  		"size": "2",
  		"peopleNum": 50,
  		"placesList": []
  	}, {
  		"id": "罗坎",
  		"pid": "镇雄县",
  		"distance": 113,
  		"size": "5",
  		"peopleNum": 40,
  		"placesList": []
  	}]
  }]
  

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