解析openweatherMap json文件

Question

我正在做一个项目，这个项目需要获取天气信息，所以我使用了openweathermap。我的程序工作正常，我从" main“和"wind”获得信息，但我也需要从主要天气set.The问题中获得描述，天气集是json文件中的一个列表，我无法将它转换为map.The示例json文件，而我正在试图解析的是http://api.openweathermap.org/data/2.5/weather?q=London。

杰森：

{
   "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
}

当我们查看这个文件时，我们注意到天气组中有一个[]括号，它在我的项目中造成了问题，我试图查找如何转换列表来映射并尝试使用我的代码，但是没有在文件中help.The注释代码是我在尝试使它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"));

    }
}

我试着用与main和way相同的方法：Map weatherMap = jsonToMap (respMap.get("weather").toString());，.But，我得到了错误：

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

因此，我试图不把json转换成Map，而是直接使用像Map weatherMap = (Map) respMap.get("weather");这样的映射，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);

但这上面写着：

//String cannot be converted to int

在这种情况下，我真的很困惑该怎么办，我不知道如何处理json文件中的[]。

Answer 1

由于这些数据是以List的形式提供的，所以您正在尝试将其转换为Map。这不对。您需要将它()作为Map的列表，然后将每个元素视为Map。下面是如何将其作为映射来获取的示例

          ///...
          //// 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);

将其转换为列表.

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

然后，将每个元素视为Map:

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

希望这能有所帮助。

Answer 2

使生活简单，使用真实的类型。

import java.util.List;

import com.google.gson.Gson;

public class PlantWateringApp {

    class Weather_2_5 {
        List<Weather> weather;
    }

    class Weather {
        Integer id;
        String main;
        String description;
        String icon;
    }

    public static void main(String[] args) {

        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);

        Gson G = new Gson();
        Weather_2_5 obj = G.fromJson(result, Weather_2_5.class);

        for (int idx = 0; idx < obj.weather.size(); idx++) {
            System.out.println(obj.weather.get(idx).description);
        }
    }
}

Answer 3

与其从一开始就把它都写下来，你可以使用：

https://github.com/xSAVIKx/openweathermap-java-api

我认为这个例子最接近你想要做的事情：

https://github.com/xSAVIKx/openweathermap-java-api/blob/development/api-examples/src/main/java/org/openweathermap/api/example/CurrentWeatherOneLocationExample.java