java - 解析openweatherMap json文件

我正在研究一个需要获取天气信息的项目，因此我使用了openweathermap api。我的程序正常工作，我从“ main”和“ wind”获得了信息，但是我还需要从主要天气集获取描述。问题是天气集是json文件中的列表，我无法进行转换我试图解析的示例json文件是http://api.openweathermap.org/data/2.5/weather?q=London

JSON：

{
   "coord":{
      "lon":-0.13,
      "lat":51.51
   },
   "weather":[
      {
         "id":803,
         "main":"Clouds",
         "description":"broken clouds",
         "icon":"04n"
      }
   ],
   "base":"stations",
   "main":{
      "temp":43.56,
      "pressure":1004,
      "humidity":87,
      "temp_min":41,
      "temp_max":46.4
   },
   "visibility":10000,
   "wind":{
      "speed":11.41,
      "deg":80
   },
   "rain":{

   },
   "clouds":{
      "all":75
   },
   "dt":1573350303,
   "sys":{
      "type":1,
      "id":1414,
      "country":"GB",
      "sunrise":1573369754,
      "sunset":1573402780
   },
   "timezone":0,
   "id":2643743,
   "name":"London",
   "cod":200
}

当我们查看文件时，我们注意到天气集内有一个[]括号，这在我的项目中造成了问题。我试图查看如何转换要映射的列表并尝试使用我的代码，但是没有帮忙。文件中的注释代码是我在尝试使其工作时尝试过的东西。

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.net.URL;
import java.net.URLConnection;
import java.util.HashMap;
import java.util.Map;

import com.google.gson.*;
import com.google.gson.reflect.*;
import java.util.List;
import java.lang.reflect.Type;

import java.util.HashMap;
import java.util.Map;

import com.google.gson.Gson;
import com.google.gson.reflect.TypeToken;

public class PlantWateringApp {

    public static Map<String, Object> jsonToMap(String str) {

        Map<String, Object> map = new Gson().fromJson(str, new TypeToken<HashMap<String, Object>>() {
        }.getType());
        return map;
    }

    public static void main(String[] args) {

        String LOCATION = "delhi,india";
        String result = "{\"coord\":{\"lon\":77.22,\"lat\":28.65},\"weather\":[{\"id\":711,\"main\":\"Smoke\",\"description\":\"smoke\",\"icon\":\"50d\"}],\"base\":\"stations\",\"main\":{\"temp\":72.32,\"pressure\":1015,\"humidity\":59,\"temp_min\":64.4,\"temp_max\":77},\"visibility\":1000,\"wind\":{\"speed\":3.36,\"deg\":270},\"clouds\":{\"all\":0},\"dt\":1573351180,\"sys\":{\"type\":1,\"id\":9165,\"country\":\"IN\",\"sunrise\":1573348168,\"sunset\":1573387234},\"timezone\":19800,\"id\":1273294,\"name\":\"Delhi\",\"cod\":200}";
        System.out.println(result);

        Map<String, Object> respMap = jsonToMap(result.toString());
        Map<String, Object> mainMap = jsonToMap(respMap.get("main").toString());
        Map<String, Object> windMap = jsonToMap(respMap.get("wind").toString());

        // Type listType = new TypeToken<List<Map<String,String>>>()
        // {}.getType();
        // List<Map<String,String>> weatherMap = new
        // Gson().fromJson(respMap.get("description").toString(),listType);

        // Map<String, Object> name = (Map<String, Object>)
        // respMap.get("description");

        // Map<String, Object > weatherMap = jsonToMap
        // (respMap.get("description").toString());

        System.out.println("Location: " + LOCATION);
        System.out.println("Current Temperature: " + mainMap.get("temp"));
        System.out.println("Current Humidity: " + mainMap.get("humidity"));
        System.out.println("Max: " + mainMap.get("temp_min"));
        System.out.println("Min: " + mainMap.get("temp_max"));

        System.out.println("Wind Speed: " + windMap.get("speed"));
        System.out.println("Wind Angle: " + windMap.get("deg"));

    }
}

我尝试做与main和wind相同的方法：Map weatherMap = jsonToMap (respMap.get("weather").toString());，但出现错误：

////java.lang.IllegalStateException: Expected BEGIN_ARRAY but was BEGIN_OBJECT at line 1 column 3 path $[0]

所以我试图不将json转换为Map，而是直接使用Map weatherMap = (Map) respMap.get("weather");这样的map，但是我得到了

////java.lang.ClassCastException: java.util.ArrayList cannot be cast to java.util.Map

为此，我尝试使用

              List<Map<String,String>> weatherMap = new Gson().fromJson(respMap.get("weather").toString(),listType);

但这说：

//String cannot be converted to int

我真的很困惑在这种情况下该怎么办。我无法弄清楚如何处理json文件中的[]。

最佳答案

由于此数据是作为List提供的，因此您正在尝试将其转换为Map。那是不对的。您需要将其（天气）作为地图列表获取，然后将每个元素都视为地图。这是一个如何获取地图的示例

          ///...
          //// other code
          ///...
          Map<String, Object > respMap = jsonToMap (result.toString());
          // don't need to convert from string to map again and again
          Map<String, Object > mainMap = (Map<String, Object >)respMap.get("main");
          Map<String, Object > windMap = (Map<String, Object >)respMap.get("wind");

          // fist get weather as list
          List<Map<String, Object >> weather = (List<Map<String, Object>>) (respMap.get("weather"));
            //...

          System.out.println("Wind Speed: " + windMap.get("speed")  );
          System.out.println("Wind Angle: " + windMap.get("deg")  );


          // weather as list
          System.out.println("Weather: "+ weather);

          // assuming weather contains at-least 1 element.
          Map<String, Object> weatherMap = weather.get(0);

          System.out.println("Weather as map: "+ weatherMap);

投射到列表。

          List<Map<String, Object >> weather = (List<Map<String, Object>>) (respMap.get("weather"));

然后将每个元素都视为Map：

// assuming weather contains at-least 1 element.
          Map<String, Object> weatherMap = weather.get(0);

希望这可以帮助。

关于java - 解析openweatherMap json文件，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/58784977/