如何从URL获取数据并将其转换为json？

Question

I am trying to get data from a URL and store it in json format using the code below:

String fullURL="http://XXX:8101/Myapp/XXX/XXX";

        URL u = new URL(fullURL);
            System.out.println(fullURL);
            HttpURLConnection huc = (HttpURLConnection) u.openConnection();
            System.out.println("Message :"+huc.getResponseMessage());
            JSONParser parser = new JSONParser();
            BufferedReader rd = new BufferedReader(new InputStreamReader(huc.getInputStream()));

            JSONArray a = (JSONArray) parser.parse(rd);

            for (Object o : a)
            {
                org.json.simple.JSONObject device = (org.json.simple.JSONObject) o;



                double kw = (double) device.get("value");
                System.out.println(kw);
                //getKw().setKw(kw);

                String sensortype = (String) device.get("senorType ");
                System.out.println(sensortype);
                //getSensorType().setSenorType(sensortype);

                Timestamp dateTime = (Timestamp) device.get("serverTimeStamp");
                System.out.println(dateTime);
                //getServerTimeStamp().setServerTimeStamp(dateTime);

  }

But I am getting the following error:

java.lang.ClassCastException: org.json.simple.JSONObject cannot be cast to org.json.simple.JSONArray.

What am I doing wrong and how to fix this?

i changed based on user comment finally my array is:

[
  {

    "value": 777,
    "percentage": 0,
    "serverTimeStamp": 1436900289000,
    "sensorType": "S"

  },
  {
    "value": 777,
    "percentage": 0,
    "serverTimeStamp": 1436900289000,
    "sensorType": "V"
  },
  {
    "value": 777,
    "percentage": 0,
    "serverTimeStamp": 1436900289000,
    "sensorType": "R"
  }
]

How come I am getting a java.lang.ClassCastException: java.lang.Long cannot be cast to java.lang.Double exception?

Answer 1

device.get("value") is returning a Long value which cannot be case to Double .

So change it to this:

long kw = (long) device.get("value");

Answer 2

After looking At your code, you are trying to cast value in double which is wrong ,you will get long instate of double when trying to get value of key "value" from JSONObject .To get your desire result first cast to long and then in double .

double kw = (double)((long) device.get("value"));

Other thing what I have observed is you are trying to cast value of key "serverTimeStamp" to Timestamp which is wrong ,instate you will get long the you have to create new Instance of Timestamp .

Timestamp dateTime = new Timestamp ((long) device.get("serverTimeStamp"));

Answer 3

Why not do it like this.

 ((Number) device.get("value")).doubleValue();

You will never get Class cast exception if the returned instace is a number like int, long, float, double etc.