GsonGetRequest.java

package team.nobugs.library.request;

import com.android.volley.NetworkResponse;
import com.android.volley.ParseError;
import com.android.volley.Request;
import com.android.volley.Response;
import com.android.volley.toolbox.HttpHeaderParser;
import com.google.gson.Gson;
import com.google.gson.JsonSyntaxException;

import java.io.UnsupportedEncodingException;
import java.lang.reflect.Type;

/**
 * Convert a JsonElement into a list of objects or an object with Google Gson.
 *
 * The JsonElement is the response object for a {@link com.android.volley.Request.Method} GET call.
 *
 * @author https://plus.google.com/+PabloCostaTirado/about
 */
public class GsonGetRequest<T> extends Request<T>
{
    private final Gson gson;
    private final Type type;
    private final Response.Listener<T> listener;

    /**
     * Make a GET request and return a parsed object from JSON.
     *
     * @param url URL of the request to make
     * @param type is the type of the object to be returned
     * @param listener is the listener for the right answer
     * @param errorListener  is the listener for the wrong answer
     */
    public GsonGetRequest
    (String url, Type type, Gson gson,
     Response.Listener<T> listener, Response.ErrorListener errorListener)
    {
        super(Method.GET, url, errorListener);

        this.gson = gson;
        this.type = type;
        this.listener = listener;
    }

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

    @Override
    protected Response<T> parseNetworkResponse(NetworkResponse response)
    {
        try
        {
            String json = new String(response.data, HttpHeaderParser.parseCharset(response.headers));

            return (Response<T>) Response.success
                    (
                            gson.fromJson(json, type),
                            HttpHeaderParser.parseCacheHeaders(response)
                    );
        }
        catch (UnsupportedEncodingException e)
        {
            return Response.error(new ParseError(e));
        }
        catch (JsonSyntaxException e)
        {
            return Response.error(new ParseError(e));
        }
    }
}