Http Get using Android HttpURLConnection

Question

I m new to Java and Android development and try to create a simple app which should contact a web server and add some data to a database using a http get   When I do the call using the web browser in my computer it works just fine  However  when I do the call running the app in the Android emulator no data is added    I have added Internet permission to the app s manifest  Logcat does not report any problems   Can anyone help me to figure out what s wrong   Here is the source code   package com example httptest   import java io IOException  import java net HttpURLConnection  import java net MalformedURLException  import java net URL  import android app Activity  import android os Bundle  import android util Log  import android widget TextView   public class HttpTestActivity extends Activity        Override     public void onCreate Bundle savedInstanceState            super onCreate savedInstanceState            TextView tv   new TextView this           setContentView tv            try               URL url   new URL  http   www mysite se index asp data 99                HttpURLConnection urlConnection    HttpURLConnection  url openConnection                urlConnection disconnect                tv setText  Hello                       catch  MalformedURLException ex                Log e  httptest  Log getStackTraceString ex                       catch  IOException ex                Log e  httptest  Log getStackTraceString ex

User · Answer

Here is a complete AsyncTask class  public class GetMethodDemo extends AsyncTask lt String   Void  String gt        String server response        Override     protected String doInBackground String    strings             URL url          HttpURLConnection urlConnection   null           try               url   new URL strings 0                urlConnection    HttpURLConnection  url openConnection                 int responseCode   urlConnection getResponseCode                 if responseCode    HttpURLConnection HTTP OK                   server response   readStream urlConnection getInputStream                     Log v  CatalogClient   server response                            catch  MalformedURLException e                e printStackTrace              catch  IOException e                e printStackTrace                       return null              Override     protected void onPostExecute String s            super onPostExecute s            Log e  Response        server response                 Converting InputStream to String  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            To Call this AsyncTask class  new GetMethodDemo   execute  your web-service url

User · Answer

Simple and Efficient Solution   use Volley   StringRequest stringRequest   new StringRequest Request Method GET  finalUrl              new Response Listener lt String gt                           Override                     public void onResponse String                           try                               JSONObject jsonObject   new JSONObject response                               HashMap lt String  Object gt  responseHashMap   new HashMap lt  gt  Utility toMap jsonObject                               catch  JSONException e                                e printStackTrace                                                                       new Response ErrorListener                  Override             public void onErrorResponse VolleyError error                    Log d  api   error getMessage   toString                                        RequestQueue queue   Volley newRequestQueue context            queue add stringRequest

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I have created with callBack delegate  response to Activity class    public class WebService extends AsyncTask lt String  Void  String gt         private Context mContext      private OnTaskDoneListener onTaskDoneListener      private String urlStr            public WebService Context context  String url  OnTaskDoneListener onTaskDoneListener            this mContext   context          this urlStr   url          this onTaskDoneListener   onTaskDoneListener              Override     protected String doInBackground String    params            try                URL mUrl   new URL urlStr               HttpURLConnection httpConnection    HttpURLConnection  mUrl openConnection                httpConnection setRequestMethod  GET                httpConnection setRequestProperty  Content-length    0                httpConnection setUseCaches false               httpConnection setAllowUserInteraction false               httpConnection setConnectTimeout 100000               httpConnection setReadTimeout 100000                httpConnection connect                 int responseCode   httpConnection getResponseCode                 if  responseCode    HttpURLConnection HTTP OK                    BufferedReader br   new BufferedReader new InputStreamReader httpConnection getInputStream                      StringBuilder sb   new StringBuilder                    String line                  while   line   br readLine       null                        sb append line     n                                      br close                    return sb toString                            catch  IOException e                e printStackTrace              catch  Exception ex                ex printStackTrace                      return null              Override     protected void onPostExecute String s            super onPostExecute s            if  onTaskDoneListener    null  amp  amp  s    null                onTaskDoneListener onTaskDone s             else             onTaskDoneListener onError              where  public interface OnTaskDoneListener       void onTaskDone String responseData        void onError        You can modify according to your needs  It s for get

User · Answer

A more contemporary way of doing it on a separate thread using Tasks and Kotlin private val mExecutor  Executor   Executors newSingleThreadExecutor    private fun createHttpTask u String   Task lt String gt        return Tasks call mExecutor  Callable lt String gt           val url   URL u          val conn  HttpURLConnection   url openConnection   as HttpURLConnection         conn requestMethod    quot GET quot          conn connectTimeout   3000         conn readTimeout   3000         val rc   conn responseCode         if   rc    HttpURLConnection HTTP OK                throw java lang Exception  quot Error    rc  quot                     val inp  InputStream   BufferedInputStream conn inputStream          val resp  String   inp bufferedReader UTF 8  use  it readText             return Callable resp           and now you can use it like below in many places              createHttpTask  quot https   google com quot                        addOnSuccessListener                           Log d  quot HTTP quot    quot Response    it  quot       it  is a response string here                                            addOnFailureListener                           Log d  quot HTTP quot    quot Error    it message  quot       it  is an Exception object here

User · Answer

If you just need a very simple call  you can use URL directly   import java net URL       new URL  http   wheredatapp com   openStream

User · Answer

Try getting the input stream from this you can then get the text data as so -      URL url      HttpURLConnection urlConnection   null      try           url   new URL  http   www mysite se index asp data 99             urlConnection    HttpURLConnection  url                  openConnection             InputStream in   urlConnection getInputStream             InputStreamReader isw   new InputStreamReader in            int data   isw read            while  data    -1                char current    char  data              data   isw read                System out print current                   catch  Exception e            e printStackTrace          finally           if  urlConnection    null                urlConnection disconnect                          You can probably use other inputstream readers such as buffered reader also   The problem is that when you open the connection - it does not  pull  any data

User · Answer

URL url   new URL  https   www google com       if you are using   URLConnection conn  url openConnection       change it to  HttpURLConnection conn   HttpURLConnection  url openConnection

[java] Http Get using Android HttpURLConnection

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