Send POST to a web service and verify some data and send back as JSON

Question

! I am working on a quiz-app that uses a PHP web service to author/host/maintain data for the Android quizes.

Heres is the PHP function in question.

I am looking for a post in my PHP code.

if (isset($_POST['verifyCourse'])){

verifyCourse($_POST['courseCode']);}

Any then this points to the function...

function verifyCourse($courseCode){

    $result = mysql_query("SELECT * FROM Course WHERE CourseCode = \"$courseCode\";");
    $rows = array();
    while ($r = mysql_fetch_assoc($result)) {
        $rows = $r;
    }

    if($rows == null){
        return 0;
    } else {
        return json_encode(array('Course' => $rows));
    }

}

And then on my Android code I am doing this to send a POST to the server called "verifyCourse" but I am getting nothing in return.

Android: Function to send HTTP POSTS

 public ArrayList<HashMap<String, String>> httpPost(List<NameValuePair> valuepair, String     code)
{
         // Create a new HttpClient and Post Header
            HttpClient httpclient = new DefaultHttpClient();
            HttpPost httppost = new HttpPost("http://mydomain.edu/quiz-app/webservice.php");
            StringBuilder builder = new StringBuilder();

            try {

                httppost.setEntity(new UrlEncodedFormEntity(valuepair));

                // Execute HTTP Post Request
                HttpResponse response = httpclient.execute(httppost);
                StatusLine statusLine = response.getStatusLine();
                int statusCode = statusLine.getStatusCode();

                /* Checking response */
                    if (statusCode == 200) {  
                        HttpEntity entity = response.getEntity();
                        InputStream in = entity.getContent(); 

                        Log.d("myapp", "response " + response.getEntity());

                        BufferedReader reader = new BufferedReader(new InputStreamReader(in));
                    String line;
                        while ((line = reader.readLine()) != null) {
                            builder.append(line);
                        } 
                }else{
                    Log.e("POST-return", "Failed to download file");
                }                       

            } catch (Exception e) {
            }
            ArrayList<HashMap<String, String>> results = new ArrayList<HashMap<String, String>>();          
            HashMap<String, String> storage =  new HashMap<String, String>(); 
            String value;
            try{
                JSONArray jArray = new JSONArray(builder.toString());
                for(int i=0; i<jArray.length(); i++){
                    JSONObject jsonObject = jArray.getJSONObject(i);
                    value=jsonObject.getString(code);
                    storage = new HashMap<String, String>();
                    storage.put(code, value);
                    results.add(storage);

                }
            } catch (Exception e) {

            }
            return results;



        }

I then am using it like this to execute the functionality. /// pass a code from other section of app public void getCourseCodesandVerify(String code) {

    List<NameValuePair> course_info = new ArrayList<NameValuePair>(2);
    course_info.add(new BasicNameValuePair("verifyCourse",null));
    course_info.add(new BasicNameValuePair("courseCode",code));
    httpPost(course_info,null);

}

Any idea why my code just returns nothing...?

Heres what I get back for JSON, how do I process this?

It seems to be your JSON string is not in an array but it could be just the object. Try to print out your JSON and show it here — kabuto178, Apr 27 '13 at 17:01
Not an answer, but you may want to consider using PDO for your database layer, as mysql_* functions are deprecated. Right now, if someone were to curl your page with a courseCode that was, for example, `"1\"; DELETE FROM Course WHERE 1=\"1"`, you could be in for a rude awakening. — dave, Apr 27 '13 at 17:23
This is a project for a university. We are going to beef it up during the summer. — wilxjcherokee, Apr 27 '13 at 18:02

score 1 · Answer 1 · edited May 23 '17 at 10:25

mysql_fetch_assoc returns an array. So in your code you get something like:

   echo json_encode(array('Course' => array()));

the result is a string: {"Course":[]}. In JSON this is an object. so you need to fetch it with:

JSONObject jsonObject = new JSONObject(jsonString);
JSONArray jArray = jsonObject.getJSONArray("Course");

See also: Reading a Json Array in android

update

in your php:

function verifyCourse($courseCode){

   $result = mysql_query("SELECT * FROM Course WHERE CourseCode = \"$courseCode\" LIMIT 1");
   $rows = array();
   while ($r = mysql_fetch_assoc($result))
   {
       $rows[]= $r;
   }   

   header('Content-type: application/json');
   return json_encode(array('Course' => $rows));
   exit;
}

Which outputs a string like:

 {"Course":[{"key1":"value1","key2":"value2"},{"2key1":"2value1","2key2":null}]}

in your java code:

        JSONObject jsonObject = new JSONObject(builder.toString());



        JSONArray jArray = jsonObject.getJSONArray("Course");



        for(int i = 0; i < jArray.length(); i++){
            JSONObject jObject = jArray.getJSONObject(i);
            Iterator<String> keys = jObject.keys();
            storage =  new HashMap<String, String>();         
            while( keys.hasNext() ){

                   String key = (String)keys.next();
                   storage.put(key, jObject.get(key).toString());

            }

            results.add(storage);
        }

Any idea how to adapt this for my code?Just change the Arrays to objects? — wilxjcherokee, Apr 27 '13 at 19:13
also does my php not work? return json_encode(array('Course' => $rows)); — wilxjcherokee, Apr 27 '13 at 19:17

Send POST to a web service and verify some data and send back as JSON

1 Answers1