com.google.gson.JsonObject cannot be cast to com.google.gson.JsonArray in Java

Question

I'm trying to place the "rates" into a JsonArray using GSON, but it doesn't work, can somebody advise how to get this JSon into a Map, or an array or something of the sort using Gson in Java?

{
  "success": true,
  "timestamp": 1548277447,
  "base": "USD",
  "date": "2019-01-23",
  "rates": {
    "AED": 3.673021,
    "ARS": 37.537301,
    "AUD": 1.400099,
    "BGN": 1.717902,
    "BRL": 3.7657,
    "BWP": 10.52802,
    "CAD": 1.334645,
    "CHF": 0.994703,
    "CLP": 671.898015,
    "CNY": 6.791896,
    "COP": 3151.5,
    "DKK": 6.559594,
    "EGP": 17.891044,
    "EUR": 0.878542,
    "GBP": 0.76529,
    "HKD": 7.84525,
    "HRK": 6.530898,
    "HUF": 279.43017,
    "ILS": 3.673794,
    "INR": 71.13502,
    "ISK": 120.350185,
    "JPY": 109.595496,
    "KRW": 1126.589831,
    "KZT": 378.239562,
    "LKR": 182.190238,
    "LTL": 2.95274,
    "LVL": 0.60489,
    "LYD": 1.390468,
    "MXN": 19.0361,
    "MYR": 4.13696,
    "NOK": 8.56596
  }
}

Edit: Added code

HttpURLConnection fixerConnection = (HttpURLConnection) url.openConnection();
          fixerConnection.setRequestMethod("GET");
          BufferedReader jsonData = new BufferedReader(new InputStreamReader(fixerConnection.getInputStream()));  
          JsonObject allData = new JsonParser().parse(jsonData).getAsJsonObject();           
          JsonArray jArray =  allData.getAsJsonArray("rates");//getAsJsonObject("symbol");

Please share your code that isn't working, as well at the line that gives you the error above. — nareddyt
– nareddyt, Commented Jan 23, 2019 at 21:48
Added, the last line gives me an error. the Json comes from an API and I place it in a buffered reader. — jackt1997
– jackt1997, Commented Jan 23, 2019 at 21:51

Bakar · Accepted Answer · 2019-01-26 08:41:09Z

5

You will get an Exception for this line here:

JsonArray jArray =  allData.getAsJsonArray("rates");

because as you can see in your input file rates is a JSON Object not an JSON array. Let me show you the difference in syntax :

1. Rates as a JSON Object(As in your case):

"rates": { "AED": 3.673021, "ARS": 37.537301}

2. Rates as a JSON Array:

"rates": [ {"AED": 3.673021}, {"ARS": 37.537301}]

In the 2nd case you can get it as JSON Array of JSON Objects! I suggest reading the DataTypes of JSON W3 Tutorial

Okay now the Solution to extracting all that stuff in your input as JSON Object

HttpURLConnection fixerConnection = (HttpURLConnection) url.openConnection();
          fixerConnection.setRequestMethod("GET");
          BufferedReader jsonData = new BufferedReader(new 
          InputStreamReader(fixerConnection.getInputStream()));  
          JsonObject allData = new JsonParser().parse(jsonData).getAsJsonObject();
          // Now Take Rates as JSON Object and capture it in a Map.
          JsonObject rates =  allData.getAsJsonObject("rates");
          Set<Map.Entry<String, JsonElement>>  entries = rates.entrySet();

edited Jan 26, 2019 at 8:41

answered Jan 24, 2019 at 9:16

Bakar

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1 Comment

nareddyt Over a year ago

Instead of storing it as a Set<Map.Entry<String, JsonElement>>, it would make more sense to store in a Map<String, JsonElement>.

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