making a GSON request using volley

Question

I have the following json response

{
  \"tag\": [
    {
      \"listing_count\": 5,
      \"listings\": [
        {
          \"source\": \"source1\",
               


        

Answer 1

Here some useful code snippets.

GsonRequest for GET petitions:

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 extends Request
{
    private final Gson gson;
    private final Type type;
    private final Response.Listener 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 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 parseNetworkResponse(NetworkResponse response)
    {
        try
        {
            String json = new String(response.data, HttpHeaderParser.parseCharset(response.headers));

            return (Response) 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));
        }
    }
}

GsonRequest for POST petitions:

    import com.android.volley.NetworkResponse;
    import com.android.volley.ParseError;
    import com.android.volley.Response;
    import com.android.volley.toolbox.HttpHeaderParser;
    import com.android.volley.toolbox.JsonRequest;
    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} POST call.
     *
     * @author https://plus.google.com/+PabloCostaTirado/about
     */
    public class GsonPostRequest extends JsonRequest
    {
        private final Gson gson;
        private final Type type;
        private final Response.Listener 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 GsonPostRequest
        (String url, String body, Type type, Gson gson,
         Response.Listener listener, Response.ErrorListener errorListener)
        {
            super(Method.POST, url, body, listener, errorListener);

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

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

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

                return (Response) 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));
            }
        }
    }

This is how you use it for JSON objects:

    /**
         * Returns a dummy object
         *
         * @param listener is the listener for the correct answer
         * @param errorListener is the listener for the error response
         *
         * @return @return {@link com.sottocorp.sotti.okhttpvolleygsonsample.api.GsonGetRequest}
         */
        public static GsonGetRequest getDummyObject
        (
                Response.Listener listener,
                Response.ErrorListener errorListener
        )
        {
            final String url = "http://www.mocky.io/v2/55973508b0e9e4a71a02f05f";

            final Gson gson = new GsonBuilder()
                    .registerTypeAdapter(DummyObject.class, new DummyObjectDeserializer())
                    .create();

            return new GsonGetRequest<>
                    (
                            url,
                            new TypeToken() {}.getType(),
                            gson,
                            listener,
                            errorListener
                    );
        }

This is how you use it for JSON arrays:

/**
     * Returns a dummy object's array
     *
     * @param listener is the listener for the correct answer
     * @param errorListener is the listener for the error response
     *
     * @return {@link com.sottocorp.sotti.okhttpvolleygsonsample.api.GsonGetRequest}
     */
    public static GsonGetRequest> getDummyObjectArray
    (
            Response.Listener> listener,
            Response.ErrorListener errorListener
    )
    {
        final String url = "http://www.mocky.io/v2/5597d86a6344715505576725";

        final Gson gson = new GsonBuilder()
                .registerTypeAdapter(DummyObject.class, new DummyObjectDeserializer())
                .create();

        return new GsonGetRequest<>
                (
                        url,
                        new TypeToken>() {}.getType(),
                        gson,
                        listener,
                        errorListener
                );
    }

This is how you use it for POST calls:

/**
     * An example call (not used in this example app) to demonstrate how to do a Volley POST call
     * and parse the response with Gson.
     *
     * @param listener is the listener for the success response
     * @param errorListener is the listener for the error response
     *
     * @return {@link com.sottocorp.sotti.okhttpvolleygsonsample.api.GsonPostRequest}
     */
    public static GsonPostRequest getDummyObjectArrayWithPost
            (
                    Response.Listener listener,
                    Response.ErrorListener errorListener
            )
    {
        final String url = "http://PostApiEndpoint";
        final Gson gson = new GsonBuilder()
                .registerTypeAdapter(DummyObject.class, new DummyObjectDeserializer())
                .create();

        final JsonObject jsonObject = new JsonObject();
        jsonObject.addProperty("name", "Ficus");
        jsonObject.addProperty("surname", "Kirkpatrick");

        final JsonArray squareGuys = new JsonArray();
        final JsonObject dev1 = new JsonObject();
        final JsonObject dev2 = new JsonObject();
        dev1.addProperty("name", "Jake Wharton");
        dev2.addProperty("name", "Jesse Wilson");
        squareGuys.add(dev1);
        squareGuys.add(dev2);

        jsonObject.add("squareGuys", squareGuys);

        return new GsonPostRequest<>
                (
                        url,
                        jsonObject.toString(),
                        new TypeToken()
                        {
                        }.getType(),
                        gson,
                        listener,
                        errorListener
                );
    }
}

All the code is taken from here, and you have a blog post about how to use OkHttp, Volley and Gson here.