parsing a json response with gson and volley. Part of http://develop-for-android.blogspot.com.es/2014/01/using-volley-in-your-application.html

GsonRequest.java

package net.colaborativa.exampleapp.api.volley;

import java.io.UnsupportedEncodingException;
import java.util.Map;

import android.util.Log;

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

public abstract class GsonRequest<T> extends Request<T> {
	protected final Gson gson = new GsonBuilder().
	  excludeFieldsWithoutExposeAnnotation().create();
	protected final Class<T> responseClass;
	protected final Listener<T> listener;
	protected Map<String, String> headers;
	
	public GsonRequest(int method, 
	  String url, 
	  Class<T> responseClass, 
	  Listener<T> listener, 
	  ErrorListener errorListener
	) {
		super(method, url, errorListener);
		this.listener = listener;
		this.responseClass = responseClass;
	}

	@Override
	public Map<String, String> getHeaders() throws AuthFailureError {
		return headers != null ? headers : super.getHeaders();
	}

	@Override
	protected void deliverResponse(T response) {
		if (listener != null)
			listener.onResponse(response);
		else
			Log.w("exampleapp", "listener was null delivering response.");
	}

	@Override
	protected Response<T> parseNetworkResponse(NetworkResponse response) {
		try {
			String json = new String(
					response.data, HttpHeaderParser.parseCharset(response.headers));
			T result = gson.fromJson(json, this.responseClass);
			return Response.success(
					result, HttpHeaderParser.parseCacheHeaders(response));
		} catch (UnsupportedEncodingException e) {
			return Response.error(new ParseError(e));
		} catch (JsonSyntaxException e) {
			return Response.error(new ParseError(e));
		}
	}
}