Question

The format of my json object is:

   String jsonObjRecv =  {
      "response":{
       "respobj":{
        "id":<int>,
        "number":<string>,
        "validated":<boolean>
         }
        },
        "status":"ok",
        "errors":null
        }

It works when code is:

        JSONObject jsonObjCont = new JSONObject(jsonObjRecv);
        String getString= jsonObjCont.toString(2);

In this case getString != null and I can receive data, but when I try to get nested data of JSON object as like:

        JSONObject jsonObjCont = new JSONObject(jsonObjRecv);
        JSONObject regNumber = jsonObjCont.getJSONObject("respobj");
        String number= regNumber.getString("number");

it dont work.

I tried to use GSON library, but it works when:

public String parse(String jsonObjRecv) {
    JsonElement jelement = new JsonParser().parse(jsonObjRecv);
    String result = jelement.toString();
    return result;

and don’t work :

public String parse(String jsonObjRecv) {
    JsonElement jelement = new JsonParser().parse(jsonObjRecv);
    JsonObject jobject = jelement.getAsJsonObject();
    jobject = jobject.getAsJsonObject("respobj");

    String result = jobject.get("number").toString();
    return result;

Where is my mistake?

Answer 1

The problem is you’re not accessing your JSON object correctly – it’s an object that contains a response object which contains a respobj object.

Gson example follows. Note the comment in the code – you need to get the response object then get the respobj from it.

public static void main( String[] args )
{
    String jsonObjRecv =  "{\"response\":{\"respobj\":{\"id\":1,\"number\":\"22\",\"validated\":true}},\"status\":\"ok\",\"errors\":null}";

    JsonElement jelement = new JsonParser().parse(jsonObjRecv);
    JsonObject jobject = jelement.getAsJsonObject();

    // Here is where you're making an error. You need to get the outer
    // 'response' object first, then get 'respobj' from that.
    jobject = jobject.getAsJsonObject("response").getAsJsonObject("respobj");

    String result = jobject.get("number").getAsString();

    System.out.println(result);

}

Output:

22

Edit to add: Note I used getAsString() vs. toString() – if you use the latter you get the raw JSON which will incluse the quotes around the value (e.g. the output would be "22")