Correct way of sending queries from Android to a remote server database

Rest api are the best method for android to remote server communication. HttpClient,volley and Fast android network library are some libraries which simplify the rest api communication. HttpClient is too slow so usage of HttpClient is not recomended. Fast Android network library is the recommended because it is simple and fast.

Usage of Fast Android Network Library

Tutorial of fast android network library

The best way to communicate between client side application and a remote database is by using RESTful API with it's famous HTTP requests GET, PUT, POST and DELETE. When you have a REST API you can have a multiple client side apps using the same database, like Android, IOS or JAVASCRIPT. And it will be secured by an API_KEY so only requests that are authorized to do the queries or modifications will be accepted.
There are many ways to create an REST API since you are a PHP developer I would recommend Slim PHP framework since it's lightweight and easy to use.

suggestions 1 : Add mySql user with certain permissions. or add permissions to sensitive tables like tables that have other user's information ...

suggestions 2 : Create an access key for every devices, refresh it in every request and give new access key as responds, if access key invalid ask the device to login in again. if login is successful, give that device new access key.

• keep a crone to clear inactive devices in time interval wises
• keep access key in SharedPreference in android devices

please check YQL they had same working idea

TRY THIS CLASS instead of volley

public class SyncToServer extends AsyncTask<String,String,String> { Context context; String url; JSONObject jsonObjectToSend; JSONArray jsonArrayToSend; OnWebServiceListener onWebServiceListener; ProgressDialog progressDialog; /** * basic initializing, only use this contractor if you don't have anything to send. * @param context it can be null, if you don't want {@link ProgressDialog} pass it as null * @param url the url for data to be passed */ public SyncToServer(Context context,String url){ this.context=context; this.url=url+""; Log.e("SyncToServer123",url+""); if(context!=null) { progressDialog = new ProgressDialog(context); progressDialog.setMessage("loading"); progressDialog.setCancelable(false); } jsonObjectToSend=null; } /** * basic initializing, only use this contractor if you had anything to send. * @param context it can be null, if you don't want {@link ProgressDialog} pass it as null * @param url the url for data to be passed * @param jsonObject the {@link JSONObject} to pass server */ public SyncToServer(Context context,String url,JSONObject jsonObject){ this.context=context; this.url=url; this.jsonObjectToSend=jsonObject; if(context!=null) { progressDialog = new ProgressDialog(context); progressDialog.setMessage("loading"); progressDialog.setCancelable(false); } } /** * basic initializing, only use this contractor if you had anything to send. * @param context it can be null, if you don't want {@link ProgressDialog} pass it as null * @param url the url for data to be passed * @param jsonObject the {@link JSONArray} to pass server */ public SyncToServer(Context context,String url,JSONArray jsonObject){ this.context=context; this.url=url; this.jsonArrayToSend=jsonObject; if(context!=null) { progressDialog = new ProgressDialog(context); progressDialog.setMessage("loading"); progressDialog.setCancelable(false); } } /** * this method will register a callback, and start web service * @param onWebServiceListener this interface used to callback mechanism */ public void start(OnWebServiceListener onWebServiceListener){ Log.i("SyncToServer123","start"); this.onWebServiceListener=onWebServiceListener; this.execute(); } @Override protected void onPreExecute() { super.onPreExecute(); Log.i("SyncToServer123","init onPre"); if(context!=null) { progressDialog.show(); } } @Override protected String doInBackground(String... strings) { HttpClient client = new DefaultHttpClient(); Log.i("SyncToServer123","doIn"); try { InputStream is; HttpPost post = new HttpPost(url); HttpResponse httpResponse; if (jsonObjectToSend != null) { Log.i("SyncToServer123", jsonObjectToSend.toString()); StringEntity se = new StringEntity(jsonObjectToSend.toString()); Log.i("SyncToServer123", jsonObjectToSend.toString()); se.setContentType(new BasicHeader(HTTP.CONTENT_TYPE, "application/json")); post.setEntity(se); post.setHeader("Accept", "application/json"); post.setHeader("Content-type", "application/json"); post.setHeader("connection", "close"); httpResponse = client.execute(post); }else if(jsonArrayToSend!=null){ Log.i("SyncToServer123", jsonArrayToSend.toString()); StringEntity se = new StringEntity(jsonArrayToSend.toString()); Log.i("SyncToServer123", jsonArrayToSend.toString()); se.setContentType(new BasicHeader(HTTP.CONTENT_TYPE, "application/json")); post.setEntity(se); post.setHeader("Accept", "application/json"); post.setHeader("Content-type", "application/json"); post.setHeader("connection", "close"); httpResponse = client.execute(post); }else{ HttpGet httpGet=new HttpGet(url); httpGet.setHeader("connection", "close"); httpResponse = client.execute(httpGet); } HttpEntity httpEntity = httpResponse.getEntity(); is = httpEntity.getContent(); try { BufferedReader reader = new BufferedReader(new InputStreamReader( is, "iso-8859-1"), 8); StringBuilder sb = new StringBuilder(); String line = null; while ((line = reader.readLine()) != null) { sb.append(line + ""); System.out.println(line); Log.i("SyncToServer123","PRE RESPONDS : "+line); } is.close(); String json = sb.toString(); JSONObject jObj; jObj = new JSONObject(json); Log.i("resultJson",json); Log.i("SyncToServer123","RESPONDS : "+json); reader.close(); httpEntity.consumeContent(); if(client != null && client.getConnectionManager() != null) { client.getConnectionManager().shutdown(); } return json; } catch (Exception e) { Log.i("SyncToServer123","Error "+e); Log.e("Buffer Error", "Error converting result " + e.toString()); } //customDbHelper.notifiSyncCompleted(); } catch (Exception e) { Log.i("SyncToServer123","Error "+e); e.printStackTrace(); } return null; } @Override protected void onPostExecute(String s) { super.onPostExecute(s); System.out.print("SyncToServer123: "+s); if(s!=null){ this.onWebServiceListener.onComplete(s); }else{ this.onWebServiceListener.onError(); } if(context!=null) { progressDialog.dismiss(); } } /** * for callbacks the web service status, */ public interface OnWebServiceListener{ /** * when service completed without any exception, including {@link JSONException} * @param result the responds given from server */ void onComplete(String result); /** * if any exception occurred this method will call */ void onError(); } } 

USAGE

SyncToServer syncToServer=new SyncToServer(null,"url",jsonObject); syncToServer.start(new SyncToServer.OnWebServiceListener() { @Override public void onComplete(String result) { } @Override public void onError() { } }); 

Library used

 useLibrary 'org.apache.http.legacy'