尽管此 JSON 有数据，但方法返回 JSON“empty:false”
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【中文标题】尽管此 JSON 有数据，但方法返回 JSON“empty:false”【英文标题】：Method returning JSON "empty:false" although this JSON has data 【发布时间】：2019-01-29 21:27:36 【问题描述】：我有 java Spring Boot 应用程序。在控制台 json 中有数据（但顺序错误？），当我将其转换为字符串时，我可以得到它，但无法返回 JSONObject，POSTman 显示 "empty":false
我的控制器 包 com.example.controller;
import java.util.List;
import javax.servlet.http.HttpServletRequest;
import org.json.JSONException;
import org.json.JSONObject;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;
import com.example.dao.SeriaDao;
import com.example.model.Seria;
@RestController
public class WebController
@Autowired
SeriaDao sed;
@GetMapping("/tabelka")
public List<Seria> showTable()
return sed.findAll();
@GetMapping("/pgTabelka")
public JSONObject pgTable(HttpServletRequest request)
int draw = 0;
int start = 0;
int length = 10;
JSONObject json = new JSONObject();
if(request.getParameter("draw")!=null)
draw = Integer.parseInt(request.getParameter("draw"));
if(request.getParameter("start")!=null)
start = Integer.parseInt(request.getParameter("start"));
if(request.getParameter("length")!=null)
length = Integer.parseInt(request.getParameter("length"));
int totalRecords = sed.recordsTotal();
List<Seria> serie = sed.findPart(start, length);
try
json.put("draw", ++draw);
json.put("recordsTotal", totalRecords);
json.put("recordsFiltered", totalRecords);
json.put("data", serie);
catch (JSONException e)
e.printStackTrace();
System.out.println(json);
return json;
我必须添加什么以及为什么我不能像我想要的那样获得 json？
PS。控制台返回的json：
"recordsFiltered": 488,
"data": [
"feed": "Macroeconomic_And_Major_Markets",
"unit": "$ per Week",
"file": "SMU48185800500000011.csv",
"cassid": "1d2e556b-031e-4c6f-aec4-981c4e907324",
"name": "Average Weekly Earnings of All Employees: Total Private in Corpus Christi, TX (MSA)",
"createdate": "2016-10-15T23:38:49",
"changedate": "2017-01-09T00:50:01",
"id": 41,
"datefrom": "2006-12-31",
"categoryid": 3,
"frequency": 5
,
"feed": "Macroeconomic_And_Major_Markets",
"unit": "Index 2015=100",
"file": "CP0910CYM086NEST.csv",
"cassid": "6df5b8d5-ec39-4860-930f-a8b355cce37a",
"name": "Harmonized Index of Consumer Prices: Audio-Visual, Photographic, and Information Processing Equipment for Cyprus",
"createdate": "2016-10-15T23:38:49",
"changedate": "2017-02-16T11:35:04",
"id": 42,
"datefrom": "1995-12-31",
"categoryid": 3,
"frequency": 5
,
"feed": "Macroeconomic_And_Major_Markets",
"unit": "$ per Week",
"file": "SMU48185800500000011A.csv",
"cassid": "c3bad2a6-7ad5-4091-846b-f84e9b9f7b50",
"name": "Average Weekly Earnings of All Employees: Total Private in Corpus Christi, TX (MSA)",
"createdate": "2016-10-15T23:38:49",
"changedate": "2017-02-16T11:32:01",
"id": 43,
"datefrom": "2006-12-31",
"categoryid": 3,
"frequency": 8
,
"feed": "Macroeconomic_And_Major_Markets",
"unit": "Index 2015=100",
"file": "CP0910CZM086NEST.csv",
"cassid": "84483d95-d914-45ab-a87a-8c063bfc6d0f",
"name": "Harmonized Index of Consumer Prices: Audio-Visual, Photographic, and Information Processing Equipment for Czech Republic",
"createdate": "2016-10-15T23:38:49",
"changedate": "2017-02-16T11:35:04",
"id": 44,
"datefrom": "1999-11-30",
"categoryid": 3,
"frequency": 5
,
"feed": "Macroeconomic_And_Major_Markets",
"unit": "$ per Week",
"file": "SMU41187000500000011SA.csv",
"cassid": "285056e3-94ce-4266-98b4-ddf32602c0c2",
"name": "Average Weekly Earnings of All Employees: Total Private in Corvallis, OR (MSA)",
"createdate": "2016-10-15T23:38:49",
"changedate": "2017-01-09T00:50:01",
"id": 45,
"datefrom": "2006-12-31",
"categoryid": 3,
"frequency": 5
,
"feed": "Macroeconomic_And_Major_Markets",
"unit": "Index 2015=100",
"file": "CP0910DKM086NEST.csv",
"cassid": "9798eadf-1503-48a5-91e3-cad5852db745",
"name": "Harmonized Index of Consumer Prices: Audio-Visual, Photographic, and Information Processing Equipment for Denmark",
"createdate": "2016-10-15T23:38:49",
"changedate": "2017-02-16T11:35:04",
"id": 46,
"datefrom": "1995-12-31",
"categoryid": 3,
"frequency": 5
,
"feed": "Macroeconomic_And_Major_Markets",
"unit": "$ per Week",
"file": "SMU41187000500000011.csv",
"cassid": "d4b22376-2f84-404f-a175-c04ad8ced5a5",
"name": "Average Weekly Earnings of All Employees: Total Private in Corvallis, OR (MSA)",
"createdate": "2016-10-15T23:38:49",
"changedate": "2017-01-09T00:50:01",
"id": 47,
"datefrom": "2006-12-31",
"categoryid": 3,
"frequency": 5
,
"feed": "Macroeconomic_And_Major_Markets",
"unit": "Index 2015=100",
"file": "CP0910EEM086NEST.csv",
"cassid": "72880ba0-722e-46bb-98f4-7d388d217c26",
"name": "Harmonized Index of Consumer Prices: Audio-Visual, Photographic, and Information Processing Equipment for Estonia",
"createdate": "2016-10-15T23:38:49",
"changedate": "2017-02-16T11:35:04",
"id": 48,
"datefrom": "1995-12-31",
"categoryid": 3,
"frequency": 5
,
"feed": "Macroeconomic_And_Major_Markets",
"unit": "$ per Week",
"file": "SMU41187000500000011A.csv",
"cassid": "03fdf50e-9cd9-483b-aecf-1a0a9e93fa4d",
"name": "Average Weekly Earnings of All Employees: Total Private in Corvallis, OR (MSA)",
"createdate": "2016-10-15T23:38:49",
"changedate": "2017-02-16T11:32:01",
"id": 49,
"datefrom": "2006-12-31",
"categoryid": 3,
"frequency": 8
,
"feed": "Macroeconomic_And_Major_Markets",
"unit": "Index 2005=100",
"file": "CP0910EZ17M086NEST.csv",
"cassid": "2943c0f2-ad55-4ec4-98d0-70db25deaefc",
"name": "Harmonized Index of Consumer Prices: Audio-Visual, Photographic, and Information Processing Equipment for Euro area (17 countries) (DISCONTINUED)",
"createdate": "2016-10-15T23:38:49",
"changedate": "2017-02-16T11:35:04",
"id": 50,
"datefrom": "1995-12-31",
"categoryid": 3,
"frequency": 5
],
"draw": 1,
"recordsTotal": 488
【问题讨论】：
我建议使用 Jackson 进行 JSON 转换。您无需编写此类代码或担心 JSON 字段排序。 Spring Boot 默认包含 Jackson。 你应该返回 json.toString() 而不是 JSONObject @SimonMartinelli 我试过了，但我需要 JSON 作为回报，因为我使用 DataTables 插件，并且数据应该以 JSON 类型发送给它... 但是如果你返回一个字符串，你会在邮递员中看到正确的 JSON 吗？ @SimonMartinelli 然后我看到了文本 【参考方案1】：Spring boot 使用 jackson 作为默认序列化程序，您正在尝试返回 JSONObject 本身。 Jackson 不知道如何序列化。
如果你想返回动态 json，你可以使用 Map 如下：
@GetMapping("/pgTabelka")
public Map<String, Object> pgTable(HttpServletRequest request)
Map<String, Object> json = new HashMap();
int draw = 0;
int start = 0;
int length = 10;
if(request.getParameter("draw")!=null)
draw = Integer.parseInt(request.getParameter("draw"));
if(request.getParameter("start")!=null)
start = Integer.parseInt(request.getParameter("start"));
if(request.getParameter("length")!=null)
length = Integer.parseInt(request.getParameter("length"));
int totalRecords = sed.recordsTotal();
List<Seria> serie = sed.findPart(start, length);
json.put("draw", ++draw);
json.put("recordsTotal", totalRecords);
json.put("recordsFiltered", totalRecords);
json.put("data", serie);
return json;
或者你可以创建一个类来代表你的 json 结构并返回你的自定义数据类作为你的响应，spring 会为你处理剩下的。
@GetMapping("/pgTabelka")
public YourJsonDataClass pgTable(HttpServletRequest request)
...
YourJsonDataClass json = new YourJsonDataClass();
json.setDraw(++draw);
json.setRecordsTotal(totalRecords);
json.setRecordsFiltered(totalRecords);
json.setData(serie);
return json;
【讨论】：
谢谢！有用。但我还有一个问题......为什么变量的顺序不是 draw->recordsTotal->recordsFiltered->data ？【参考方案2】：使用 HashMap 代替 JSONObject
List<HashMap<String, String>> myList = new ArrayList<HashMap<String, String>>();
HashMap<String, String> map = new HashMap<>();
map.put(key, value);
myList.add(map);
如果你有一个 ResultSet，你可以通过 rs 循环这段代码。 值得注意的是，如果你的 HashMap 有重复的键，你将不得不使用 Multimap，因为 HashMap 不允许重复的键
Multimap<String, String> map = ArrayListMultimap.create();
map.put(key1, "value1");
map.put(key1, "value2");
map.put(key2, "value3");
【讨论】：
【参考方案3】：使用泛型类型ResponseEntity<?> 结合json.toString() 可以解决问题。
@ResponseBody
public ResponseEntity<?> create(@RequestBody User user)
return ResponseEntity.status(HttpStatus.OK).body(json.toString());
【讨论】：
【参考方案4】：我收到这个错误是因为我写了
JSONObject j1 = method()
JSONObject j2 = new JSONObject(j1)
【讨论】：
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