Simple HttpURLConnection wrapper class

HttpRequest.java

package com.amitaymolko.network;

import java.util.HashMap;

/**
 * Created by amitaymolko on 2/16/16.
 */

public class HttpRequest {

    public interface RequestCallback {
        void onResponse(HttpResponse r);
    }

    public enum Method {
        GET,
        POST,
        UPDATE,
        DELETE
    }

    private Method method;
    private String URL;
    private HashMap<String, String> headers;
    private String postData;
    private RequestCallback callback;

    public HttpRequest(Method method, String URL) {
        this.method = method;
        this.URL = URL;
    }

    public HttpRequest(Method method, String URL, String postData) {
        this.method = method;
        this.URL = URL;
        this.postData = postData;
    }

    public Method getMethod() {
        return method;
    }

    public void setMethod(Method method) {
        this.method = method;
    }

    public String getMethodString() {
        return method.toString();
    }

    public String getURL() {
        return URL;
    }

    public void setURL(String URL) {
        this.URL = URL;
    }

    public HashMap<String, String> getHeaders() {
        return headers;
    }

    public void setHeaders(HashMap<String, String> headers) {
        this.headers = headers;
    }

    public String getPostData() {
        return postData;
    }

    public void setPostData(String postData) {
        this.postData = postData;
    }

    public RequestCallback getCallback() {
        return callback;
    }

    public void setCallback(RequestCallback callback) {
        this.callback = callback;
    }

}

HttpResponse.java

package com.amitaymolko.network;

/**
 * Created by amitaymolko on 2/16/16.
 */
public class HttpResponse {
    private int responseCode;
    private String response;
    private HttpRequest.RequestCallback callback;

    public HttpResponse(int responseCode, String response, HttpRequest.RequestCallback callback) {
        this.responseCode = responseCode;
        this.response = response;
        this.callback = callback;
    }

    public HttpResponse() {

    }

    public int getResponseCode() {
        return responseCode;
    }

    public void setResponseCode(int responseCode) {
        this.responseCode = responseCode;
    }

    public String getResponse() {
        return response;
    }

    public void setResponse(String response) {
        this.response = response;
    }

    public HttpRequest.RequestCallback getCallback() {
        return callback;
    }

    public void setCallback(HttpRequest.RequestCallback callback) {
        this.callback = callback;
    }
}

HttpTask.java

package com.amitaymolko.network;

import android.os.AsyncTask;
import android.util.Log;

import java.io.BufferedReader;
import java.io.DataOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.URL;
import java.util.HashMap;

import javax.net.ssl.HttpsURLConnection;

/**
 * Created by amitaymolko on 2/16/16.
 */

public class HttpTask extends AsyncTask<HttpRequest, String, HttpResponse> {

    @Override
    protected HttpResponse doInBackground(HttpRequest... params) {
        URL url;
        HttpURLConnection urlConnection = null;
        HttpResponse response = new HttpResponse();

        try {
            HttpRequest request = params[0];
            if (request == null || request.getURL() == null || request.getMethod() == null) {
                Log.e("HttpTask", "BAD HttpRequest");
                throw new Exception();
            }
            url = new URL(request.getURL());
            urlConnection = (HttpURLConnection) url.openConnection();
            Log.v("HttpTask", request.getMethodString());

            urlConnection.setRequestMethod(request.getMethodString());

            if (request.getHeaders() != null) {
                for (HashMap.Entry<String, String> pair : request.getHeaders().entrySet()) {
                    urlConnection.setRequestProperty(pair.getKey(), pair.getValue());
                }
            }
            urlConnection.setConnectTimeout(10000);
            urlConnection.setReadTimeout(10000);
            if (request.getPostData() != null) {
                urlConnection.setDoOutput(true);
                    DataOutputStream wr = new DataOutputStream( urlConnection.getOutputStream());
                    byte[] postData       = request.getPostData().getBytes();
                    wr.write( postData );
            }
            urlConnection.connect();

            int responseCode = urlConnection.getResponseCode();
            String responseString;
            if(responseCode == HttpsURLConnection.HTTP_OK){
                responseString = readStream(urlConnection.getInputStream());
            }else{
                responseString = readStream(urlConnection.getErrorStream());
            }
            Log.v("HttpTask", "Response code:"+ responseCode);
            Log.v("HttpTask", responseString);
            response = new HttpResponse(responseCode, responseString, request.getCallback());

        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            if(urlConnection != null)
                urlConnection.disconnect();
        }

        return response;
    }

    private String readStream(InputStream in) {
        BufferedReader reader = null;
        StringBuffer response = new StringBuffer();
        try {
            reader = new BufferedReader(new InputStreamReader(in));
            String line = "";
            while ((line = reader.readLine()) != null) {
                response.append(line);
            }
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            if (reader != null) {
                try {
                    reader.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
        return response.toString();
    }

    @Override
    protected void onPostExecute(HttpResponse response) {
        super.onPostExecute(response);
        response.getCallback().onResponse(response);
    }
}

JsonAPI.java

package com.amitaymolko.network;

import org.json.JSONException;
import org.json.JSONObject;

import java.util.HashMap;

/**
 * Created by amitaymolko on 2/19/16.
 */
public class JsonAPI {

    public interface JsonCallback {
        void onResponse(int statusCode, JSONObject json);
    }

    private static JsonAPI ourInstance = new JsonAPI();
    private HashMap<String, String> headers = new HashMap<>();
    public static JsonAPI getInstance() {
        return ourInstance;
    }

    private JsonAPI() {
        headers.put("Content-Type","application/json");
        headers.put("Accept","application/json");
    }

    public void addHeader(String name, String value) {
        headers.put(name, value);
    }
    public void removeHeader(String name) {
        headers.remove(name);
    }

    public void get(String url, final JsonCallback callback) {
        HttpRequest r = new HttpRequest(HttpRequest.Method.GET, url);
        r.setHeaders(headers);
        r.setCallback(callbackForJsonCallback(callback));
        new HttpTask().execute(r);
    }

    public void post(String url, JSONObject postData, JsonCallback callback) {
        HttpRequest r = new HttpRequest(HttpRequest.Method.POST, url);
        r.setHeaders(headers);
        r.setCallback(callbackForJsonCallback(callback));
        r.setPostData(postData.toString());
        new HttpTask().execute(r);
    }

    private HttpRequest.RequestCallback callbackForJsonCallback(final JsonCallback jsonCallback) {
        return new HttpRequest.RequestCallback() {
            @Override
            public void onResponse(HttpResponse r) {
                JSONObject json = null;
                try {
                    json =  new JSONObject(r.getResponse());
                } catch (JSONException e) {
                    e.printStackTrace();
                }
                jsonCallback.onResponse(r.getResponseCode(), json);
            }
        };
    }
}

login-example.txt

String url = "http://37.139.3.222/login";
JSONObject json = new JSONObject();
try {
    json.put("email", emailEditText.getText().toString());
    json.put("password", passwordEditText.getText().toString());

    JsonAPI.getInstance().post(url, json, new JsonAPI.JsonCallback() {
        @Override
        public void onResponse(int statusCode, JSONObject json) {
            if (statusCode == 200) {
                String token = null;
                try {
                    token = json.getString("token");
                    JsonAPI.getInstance().addHeader("Token", token);
                    LoginActivity.this.finish();
                } catch (JSONException e) {
                    e.printStackTrace();
                }
            }
        }
    });

} catch (JSONException e) {
    e.printStackTrace();
}