Parsing json object from google api returning null

Question

I am making a simple application where i scan the barcode of a book and fetch its title and author from Google APIs,

Now, this is the url for json(for a particular book i am scanning)

https://www.googleapis.com/books/v1/volumes?q=isbn:9788120305960

using this code to get json in a string

HttpURLConnection urlConnection  = (HttpURLConnection)url.openConnection();
        InputStream inputStream = urlConnection.getInputStream();
        BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(inputStream,"iso-8859-1"));
        String line = "";

        while ((line=bufferedReader.readLine())!=null)
        {
            response+=line;
        }

        bufferedReader.close();
        inputStream.close();
        urlConnection.disconnect();
        Log.d("Info",response);
        return response;

I store the result in a string and use this code to parse through (json_response is a string)

            JSONObject rootObject = new JSONObject(json_response);
            JSONArray items = rootObject.getJSONArray("items");
            JSONObject items_object = items.getJSONObject(0);
            JSONObject volume_info = items_object.getJSONObject("volumeInfo");
            book.setTitle(volume_info.getString("title"));
            JSONArray authors = volume_info.getJSONArray("authors");
            Log.d("Info","authors array length: "+authors.length());
            String author="";
            for (int i =0;i<authors.length();i++)
            {
                author+=authors.getString(i)+", ";
            }

            book.setAuthor(author);

The exception is:

Value null of type org.json.JSONObject$1 cannot be converted to JSONObject

also I used logcat to see what is contained in json_response it looks something like this

null{ "kind": "books#volumes", "totalItems": 1, "items":...

The null here is probably causing the problem, so... any insights how to deal with this???

PS: I am a student , dealing first time with json and android, code is unprofessional, please pardon :)

You should initialise the variable response to empty string. Does it help? — Lino
– Lino, Commented Jun 26, 2016 at 17:13
You can use the Volley to get a response from the google. After that use the GSON that will ease your work while parsing the JSON. — Aman Jain
– Aman Jain, Commented Jun 26, 2016 at 17:16
ok I will add it as answer. Please accept it if you found useful — Lino
– Lino, Commented Jun 26, 2016 at 18:33

Lino · Accepted Answer · 2016-06-26 18:36:31Z

1

Having

null{ "kind": "books#volumes", "totalItems": 1, "items":...

means that the response value has not been initialised.

You should therefore initialise it to empty string.

answered Jun 26, 2016 at 18:36

Lino

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