我无法从 json 文件中读取和打印值

Question

So I'm trying to read and print the json file as a string in the JAVA console. Instead of printing json content, program is printing the default attribute values of reference class. How can I resolve this problem? My code is like this

public class test {

 

       private static final String WEATHER_URL = "https://api.collectapi.com/weather/getWeather?data.lang=tr&data.city=istanbul";
    
        public static void main(String[] args) throws IOException, InterruptedException {
    
            HttpClient client = HttpClient.newHttpClient();
            HttpRequest request = (HttpRequest) HttpRequest.newBuilder()
                    .GET()
                    .header("content-type", "application/json")
                    .header("authorization", "apikey myapikey")
                    .uri(URI.create(WEATHER_URL))
                    .build();
    
            HttpResponse<String> response = client.send(request, HttpResponse.BodyHandlers.ofString());




//parse JSON into objects 
    
    
    ObjectMapper mapper = new ObjectMapper();
    
mapper.configure(DeserializationFeature.ACCEPT_SINGLE_VALUE_AS_ARRAY, true);
mapper.disable(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES);
mapper.setVisibility(VisibilityChecker.Std.defaultInstance().withFieldVisibility(JsonAutoDetect.Visibility.ANY));

List<Data>data = mapper.readValue(response.body(), new TypeReference<List<Data>>() { });


   
        System.out.println(data);

//CONSOLE OUTPUT
[Data{date=null, day=null, icon=null, description=null, status=null, degree=0.0, min=0.0, max=0.0, night=0.0, humidity=0}]
------------------------------------------------------------------------
BUILD SUCCESS

//DATA CLASS

public class Data {
  
  

      private String date;
        private String day ; 
        private String icon ; 
        private String description;
        private String status ;
        private double degree;
        private double min;
        private double max ; 
        private double night ; 
        private int humidity;

//getters and setters are here

@Override
    public String toString() {
        return "Data{" + "date=" + date + ", day=" + day + ", icon=" + icon + ", description=" + description + ", status=" + status + ", degree=" + degree + ", min=" + min + ", max=" + max + ", night=" + night + ", humidity=" + humidity + '}';
    }

//JSON FILE STRUCTURE IS LIKE THIS

{
  "result": [
    {
      "date": "24.09.2018",
      "day": "Pazartesi",
      "icon": "https://image.flaticon.com/icons/svg/143/143769.svg",
      "description": "açık",
      "status": "Clear",
      "degree": "31",
      "min": "11.6",
      "max": "31",
      "night": "11.6",
      "humidity": "17"
    },
    {
      "date": "25.09.2018",
      "day": "Salı",
      "icon": "https://image.flaticon.com/icons/svg/143/143769.svg",
      "description": "yağmurlu",
      "status": "Rainy",
      "degree": "24.14",
      "min": "7.63",
      "max": "25.82",
      "night": "9.09",
      "humidity": "35"
    },
    "..."
  ]
}

Answer 1

Add Apache common utils to pom and it will work like charm

import org.apache.commons.io.IOUtils; 
    
    

String theJsonString = ""; 
    
     
 
 theJsonString=IOUtils.toString(classLoader.getResourceAsStream("/path/file.json"));

Answer 2

The way you have parsed the response seems wrong to me. JSON file structure response doesn't start with a JSONArray, the actual JSON response is an object which has a key named result which is an array of JSONObject , so the line below won't work here.

List<Data>data = mapper.readValue(response.body(), new TypeReference<List<Data>>() { });

response.body() isn't returning an array it's an object, so if you want to get array out of the response you need to first get the result and then you can parse the array.

You may need to update the POJO first:

    public class Response {
        private Data result;
    }

    class Data {
        private String date;
        private String day ;
        private String icon ;
        private String description;
        private String status ;
        private double degree;
        private double min;
        private double max ;
        private double night ;
        private int humidity;
    }

Then something like this can parse:

final Response response = mapper.readValue(response.body(), new TypeReference<Response>() { });
final List<Data> data = response.result