Custom Volley-Gson request implementation

This page covers Volley-Gson integration and also Volley custom Request. We assume that, you are familiar with Volley and Gson.

Volley has some inbuilt request which you can use, if your response is a String, Image, or JSON, in that case, you don't need to implement a custom Request.  To use Gson with Volley, we need to implement a custom request.
To make a custom request, you need to perform following operation.

1. Extend Request<T> class, where T is the type of parsed response or expected response.
2. Implement the abstract methods parseNetworkResponse() and deliverResponse().

 parseNetworkResponse:

 A response contains parse response of a given type i.e Gson.

@Override
    protected Response<T> parseNetworkResponse(NetworkResponse response) {
        try {
            String json = new String(
                    response.data, HttpHeaderParser.parseCharset(response.headers));
            if (BuildConfig.IS_DEBUG)
                Log.d(TAG, "Response :: " + response.data == null ? null : new String(response.data));
            return Response.success(
                    mGson.fromJson(json, mClass), HttpHeaderParser.parseCacheHeaders(response));
        } catch (UnsupportedEncodingException ex) {
            return Response.error(new ParseError(ex));
        } catch (JsonSyntaxException ex) {
            return Response.error(new ParseError(ex));
        }
    }

deliverResponse:

This is callback interface which Volley use to call back you on the main thread using the Object you returned in parseNetworkResponse().

@Override
    protected void deliverResponse(T response) {
        mListener.onResponse(response);
    }

Complete Code:

 public class GSONRequest<T> extends Request<T> {
    private static final String TAG = "GSONRequest";
    private final Class<T> mClass;
    private final Response.Listener<T> mListener;
    private final Gson mGson = new Gson();

    /**
     * Make a POST request and return a parsed object from JSON.
     *
     * @param url           for request
     * @param tClass        Gson reflection class object
     * @param listener      responce listener
     * @param errorListener responce error listener
     */
    public GSONRequest(String url, Class<T> tClass,
                       Response.Listener<T> listener, Response.ErrorListener errorListener) {
        super(Method.POST, url, errorListener);
        mClass = tClass;
        mListener = listener;
    }

    @Override
    public byte[] getBody() throws AuthFailureError {
        return super.getBody();
    }

    @Override
    protected void deliverResponse(T response) {
        mListener.onResponse(response);
    }

    @Override
    protected Response<T> parseNetworkResponse(NetworkResponse response) {
        try {
            String json = new String(
                    response.data, HttpHeaderParser.parseCharset(response.headers));
            if (BuildConfig.IS_DEBUG)
                Log.d(TAG, "Response :: " + response.data == null ? null : new String(response.data));
            return Response.success(
                    mGson.fromJson(json, mClass), HttpHeaderParser.parseCacheHeaders(response));
        } catch (UnsupportedEncodingException ex) {
            return Response.error(new ParseError(ex));
        } catch (JsonSyntaxException ex) {
            return Response.error(new ParseError(ex));
        }
    }
}
 

Source Code download