Java - Taking the value of a specific JSON element

Question

I am using the exchangerate API (https://www.exchangerate-api.com) to pick up the currency quotes of the day.

Using the code below I get a Jsonobject containing the "rates":

   private JsonObject getExchangesRate() throws JsonIOException, JsonSyntaxException, IOException {

    // Setting URL
    String url_str = "https://v3.exchangerate-api.com/bulk/f75b7f1b080c9060121e6754/BRL";

    // Making Request
    URL url = new URL(url_str);
    HttpURLConnection request = (HttpURLConnection) url.openConnection();
    request.connect();

    // Convert to JSON
    JsonParser jp = new JsonParser();
    JsonElement root = jp.parse(new InputStreamReader((InputStream) request.getContent()));
    JsonObject jsonobj = root.getAsJsonObject();

    // Accessing object
    return jsonobj;

}

Theoretically, it’s supposed to come in this format:

{
   "result": "success",
   "from": "USD",
   "rates": {
      "AUD": ((AUD in terms of USD)),
      "BGN": 1.8096,
      "BRL": 3.1143,
      "...": 1.3113,
      "...": 7.473, etc. etc.
   }
}

I am trying to take the values inside the key "rates" and store the values of USD, EUR and GBP.

But I’m not getting it. I read about how JSON works in Java but I’m still not able to do what I want.

JsonObject resultadoJSON = getExchangesRate();      

    JsonElement rates = resultadoJSON.get("rates");
    double ValorUSD = (double) rates.get("USD"); //Sei que não é assim, mas é o que to tentando fazer
    double ValorEUR = (double) rates.get("EUR"); //Sei que não é assim, mas é o que to tentando fazer

Answer 1

You can add a cast in the rates object as a Jsonobject and right after, take the respective values of the converted currencies as Jsonelement:

public JsonElement getExchangesRate() throws JsonIOException, JsonSyntaxException, IOException {

        // Setting URL
        String url_str = "https://v3.exchangerate-api.com/bulk/f75b7f1b080c9060121e6754/BRL";

        // Making Request
        URL url = new URL(url_str);
        HttpURLConnection request = (HttpURLConnection) url.openConnection();
        request.connect();

        // Convert to JSON
        JsonParser jp = new JsonParser();
        JsonElement root = jp.parse(new InputStreamReader((InputStream) request.getContent()));
        JsonObject jsonobj = root.getAsJsonObject();
        JsonObject rates = (JsonObject) jsonobj.get("rates");



        // Accessing element
        return rates.get("USD");

    }

Answer 2

I was able to solve it this way:

JsonObject JSONResult = getExchangesRate(); 
JsonObject rates =  JSONResult.getAsJsonObject("rates");

Double ValorUSD = 1 / rates.get("USD").getAsDouble(); 
Double ValorEUR = 1 / rates.get("EUR").getAsDouble();
Double ValorGBP = 1 / rates.get("GBP").getAsDouble();   //English Pounds

The problem was that the package you were using is GSON (as specified on the API website) and not normal Java JSON. That’s why in the ordinary way I wasn’t getting.