[FIXED] How can I analyse JSON in Java?

Issue

I am doing a project for the Mobile Application Development unit. I am to read and parse the JSON from https://jsonplaceholder.typicode.com/users and display it in a list.

I am unsure on how the JSON can be parsed.

I am currently using the following script, but getting the JSONTypeMismatch error.

Any help is appreciated. Thanks in advance.

try
        {
            URL url = new URL("https://jsonplaceholder.typicode.com/users");
            con = (HttpURLConnection) url.openConnection();
            con.connect();

            JSONObject jBase = new JSONObject(IOUtils.toString(con.getInputStream(), StandardCharsets.UTF_8));

            JSONArray data = new JSONArray(IOUtils.toString(con.getInputStream(), StandardCharsets.UTF_8));
            

            for (int i = 0; i < data.length(); i++)
            {
                JSONObject user = data.getJSONObject(i);
                users.add(new User(user.getInt("id"), user.getString("name"), user.getString("username"), user.getString("email"), user.getJSONObject("address"), user.getString("phone"), user.getString("website"), user.getJSONObject("company")));
            }
        }
        catch (MalformedURLException e) {Toast.makeText(getApplicationContext(), "Malformed URL!", Toast.LENGTH_SHORT).show();}
        catch (IOException e)           {Toast.makeText(getApplicationContext(), "IOException!", Toast.LENGTH_SHORT).show();}
        catch (IllegalStateException e) {Toast.makeText(getApplicationContext(), "HTTP Error!", Toast.LENGTH_SHORT).show();}
        catch (JSONException e)         {e.printStackTrace();}
        finally                         {con.disconnect();}

Solution

To parse json into an object there are a couple of libraries you can use which makes it easier to parse. One of which is GSON Library

First add Gson to your app level gradle file.

  implementation 'com.google.code.gson:gson:2.9.1'

After that you can use below code to parse your required json. This is an example to parse a JSONObject to an object class. Array can be parsed a bit differently

User userModel = new Gson().fromJson(
                json.optJSONObject("data").toString(),
                User.java)

To parse JsonArray as in your case below code can be used.

Gson gson = new Gson();
String jsonOutput =  json.optJSONArray("data").toString();
Type listType = new TypeToken<List<User>>(){}.getType();
List<User> userList = gson.fromJson(jsonOutput, listType);

Answered By - Shahnawaz Ansari
Answer Checked By - David Marino (JavaFixing Volunteer)