Sending POST data in Android

Note (Oct 2020): AsyncTask used in the following answer has been deprecated in Android API level 30. Please refer to Official documentation or this blog post for a more updated example

Updated (June 2017) Answer which works on Android 6.0+. Thanks to @Rohit Suthar, @Tamis Bolvari and @sudhiskr for the comments.

    public class CallAPI extends AsyncTask<String, String, String> {
    
        public CallAPI(){
            //set context variables if required
        }
    
        @Override
        protected void onPreExecute() {
            super.onPreExecute();
        }
    
         @Override
         protected String doInBackground(String... params) {
            String urlString = params[0]; // URL to call
            String data = params[1]; //data to post
            OutputStream out = null;

            try {
                URL url = new URL(urlString);
                HttpURLConnection urlConnection = (HttpURLConnection) url.openConnection();
                out = new BufferedOutputStream(urlConnection.getOutputStream());

                BufferedWriter writer = new BufferedWriter(new OutputStreamWriter(out, "UTF-8"));
                writer.write(data);
                writer.flush();
                writer.close();
                out.close();

                urlConnection.connect();
            } catch (Exception e) {
                System.out.println(e.getMessage());
            }
        }
    }

References:

• https://developer.android.com/reference/java/net/HttpURLConnection.html
• How to add parameters to HttpURLConnection using POST using NameValuePair

Original Answer (May 2010)

Note: This solution is outdated. It only works on Android devices up to 5.1. Android 6.0 and above do not include the Apache http client used in this answer.

Http Client from Apache Commons is the way to go. It is already included in android. Here's a simple example of how to do HTTP Post using it.

public void postData() {
    // Create a new HttpClient and Post Header
    HttpClient httpclient = new DefaultHttpClient();
    HttpPost httppost = new HttpPost("http://www.yoursite.com/script.php");

    try {
        // Add your data
        List<NameValuePair> nameValuePairs = new ArrayList<NameValuePair>(2);
        nameValuePairs.add(new BasicNameValuePair("id", "12345"));
        nameValuePairs.add(new BasicNameValuePair("stringdata", "Hi"));
        httppost.setEntity(new UrlEncodedFormEntity(nameValuePairs));

        // Execute HTTP Post Request
        HttpResponse response = httpclient.execute(httppost);
        
    } catch (ClientProtocolException e) {
        // TODO Auto-generated catch block
    } catch (IOException e) {
        // TODO Auto-generated catch block
    }
} 

for Android = > 5

The org.apache.http classes and the AndroidHttpClient class have been deprecated in Android 5.1. These classes are no longer being maintained and you should migrate any app code using these APIs to the URLConnection classes as soon as possible.

https://developer.android.com/about/versions/android-5.1.html#http

Thought of sharing my code using HttpUrlConnection

public String  performPostCall(String requestURL,
        HashMap<String, String> postDataParams) {

    URL url;
    String response = "";
    try {
        url = new URL(requestURL);

        HttpURLConnection conn = (HttpURLConnection) url.openConnection();
        conn.setReadTimeout(15000);
        conn.setConnectTimeout(15000);
        conn.setRequestMethod("GET");
        conn.setDoInput(true);
        conn.setDoOutput(true);


        OutputStream os = conn.getOutputStream();
        BufferedWriter writer = new BufferedWriter(
                new OutputStreamWriter(os, "UTF-8"));
        writer.write(getPostDataString(postDataParams));

        writer.flush();
        writer.close();
        os.close();
        int responseCode=conn.getResponseCode();

        if (responseCode == HttpsURLConnection.HTTP_OK) {
            String line;
            BufferedReader br=new BufferedReader(new InputStreamReader(conn.getInputStream()));
            while ((line=br.readLine()) != null) {
                response+=line;
            }
        }
        else {
            response="";    

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

    return response;
}

...

private String getPostDataString(HashMap<String, String> params) throws UnsupportedEncodingException{
        StringBuilder result = new StringBuilder();
        boolean first = true;
        for(Map.Entry<String, String> entry : params.entrySet()){
            if (first)
                first = false;
            else
                result.append("&");

            result.append(URLEncoder.encode(entry.getKey(), "UTF-8"));
            result.append("=");
            result.append(URLEncoder.encode(entry.getValue(), "UTF-8"));
        }

        return result.toString();
    }

also you can Post method :

conn.setRequestMethod("POST");

Update 21/02/2016

for post request with json , see this example :

public class Empty extends
        AsyncTask<Void, Void, Boolean> {

    String urlString = "http://www.yoursite.com/";

    private final String TAG = "post json example";
    private Context context;

    private int advertisementId;

    public Empty(Context contex, int advertisementId) {

        this.context = contex;
        this.advertisementId = advertisementId;
    }

    @Override
    protected void onPreExecute() {
        Log.e(TAG, "1 - RequestVoteTask is about to start...");

    }

    @Override
    protected Boolean doInBackground(Void... params) {
        boolean status = false;

        String response = "";
        Log.e(TAG, "2 - pre Request to response...");

        try {
            response = performPostCall(urlString, new HashMap<String, String>() {

                        private static final long serialVersionUID = 1L;

                        {
                            put("Accept", "application/json");
                            put("Content-Type", "application/json");
                        }
                    });
            Log.e(TAG, "3 - give Response...");
            Log.e(TAG, "4 " + response.toString());
        } catch (Exception e) {
            // displayLoding(false);

            Log.e(TAG, "Error ...");
        }
        Log.e(TAG, "5 - after Response...");

        if (!response.equalsIgnoreCase("")) {
            try {
                Log.e(TAG, "6 - response !empty...");
                //
                JSONObject jRoot = new JSONObject(response);
                JSONObject d = jRoot.getJSONObject("d");

                int ResultType = d.getInt("ResultType");
                Log.e("ResultType", ResultType + "");

                if (ResultType == 1) {

                    status = true;

                }

            } catch (JSONException e) {
                // displayLoding(false);
                // e.printStackTrace();
                Log.e(TAG, "Error " + e.getMessage());
            } finally {

            }
        } else {
            Log.e(TAG, "6 - response is empty...");

            status = false;
        }

        return status;
    }

    @Override
    protected void onPostExecute(Boolean result) {
        //
        Log.e(TAG, "7 - onPostExecute ...");

        if (result) {
            Log.e(TAG, "8 - Update UI ...");

            // setUpdateUI(adv);
        } else {
            Log.e(TAG, "8 - Finish ...");

            // displayLoding(false);
            // finish();
        }

    }

    public String performPostCall(String requestURL,
                                  HashMap<String, String> postDataParams) {

        URL url;
        String response = "";
        try {
            url = new URL(requestURL);

            HttpURLConnection conn = (HttpURLConnection) url.openConnection();
            conn.setReadTimeout(context.getResources().getInteger(
                    R.integer.maximum_timeout_to_server));
            conn.setConnectTimeout(context.getResources().getInteger(
                    R.integer.maximum_timeout_to_server));
            conn.setRequestMethod("POST");
            conn.setDoInput(true);
            conn.setDoOutput(true);

            conn.setRequestProperty("Content-Type", "application/json");

            Log.e(TAG, "11 - url : " + requestURL);

            /*
             * JSON
             */

            JSONObject root = new JSONObject();
            //
            String token = Static.getPrefsToken(context);

            root.put("securityInfo", Static.getSecurityInfo(context));
            root.put("advertisementId", advertisementId);

            Log.e(TAG, "12 - root : " + root.toString());

            String str = root.toString();
            byte[] outputBytes = str.getBytes("UTF-8");
            OutputStream os = conn.getOutputStream();
            os.write(outputBytes);

            int responseCode = conn.getResponseCode();

            Log.e(TAG, "13 - responseCode : " + responseCode);

            if (responseCode == HttpsURLConnection.HTTP_OK) {
                Log.e(TAG, "14 - HTTP_OK");

                String line;
                BufferedReader br = new BufferedReader(new InputStreamReader(
                        conn.getInputStream()));
                while ((line = br.readLine()) != null) {
                    response += line;
                }
            } else {
                Log.e(TAG, "14 - False - HTTP_OK");
                response = "";
            }
        } catch (Exception e) {
            e.printStackTrace();
        }

        return response;
    }
}

UPDATE 24/08/2016

Use some best library , such as :

• Retrofit
• Volley

because :

• Avoid HttpUrlConnection and HttpClient

On lower API levels (mostly on Gingerbread and Froyo), HttpUrlConnection and HttpClient are far from being perfect

• And Avoid AsyncTask Too
• They are Much Faster
• They Caches Everything

Since the introduction of Honeycomb (API 11), it's been mandatory to perform network operations on a separate thread, different from the main thread

By this way we can send data with http post method and get result

     public class MyHttpPostProjectActivity extends Activity implements OnClickListener {

    private EditText usernameEditText;
    private EditText passwordEditText;
    private Button sendPostReqButton;
    private Button clearButton;

    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.login);

        usernameEditText = (EditText) findViewById(R.id.login_username_editText);
        passwordEditText = (EditText) findViewById(R.id.login_password_editText);

        sendPostReqButton = (Button) findViewById(R.id.login_sendPostReq_button);
        sendPostReqButton.setOnClickListener(this);

        clearButton = (Button) findViewById(R.id.login_clear_button);
        clearButton.setOnClickListener(this);        
    }

    @Override
    public void onClick(View v) {

        if(v.getId() == R.id.login_clear_button){
            usernameEditText.setText("");
            passwordEditText.setText("");
            passwordEditText.setCursorVisible(false);
            passwordEditText.setFocusable(false);
            usernameEditText.setCursorVisible(true);
            passwordEditText.setFocusable(true);
        }else if(v.getId() == R.id.login_sendPostReq_button){
            String givenUsername = usernameEditText.getEditableText().toString();
            String givenPassword = passwordEditText.getEditableText().toString();

            System.out.println("Given username :" + givenUsername + " Given password :" + givenPassword);

            sendPostRequest(givenUsername, givenPassword);
        }   
    }

    private void sendPostRequest(String givenUsername, String givenPassword) {

        class SendPostReqAsyncTask extends AsyncTask<String, Void, String>{

            @Override
            protected String doInBackground(String... params) {

                String paramUsername = params[0];
                String paramPassword = params[1];

                System.out.println("*** doInBackground ** paramUsername " + paramUsername + " paramPassword :" + paramPassword);

                HttpClient httpClient = new DefaultHttpClient();

                // In a POST request, we don't pass the values in the URL.
                //Therefore we use only the web page URL as the parameter of the HttpPost argument
                HttpPost httpPost = new HttpPost("http://www.nirmana.lk/hec/android/postLogin.php");

                // Because we are not passing values over the URL, we should have a mechanism to pass the values that can be
                //uniquely separate by the other end.
                //To achieve that we use BasicNameValuePair             
                //Things we need to pass with the POST request
                BasicNameValuePair usernameBasicNameValuePair = new BasicNameValuePair("paramUsername", paramUsername);
                BasicNameValuePair passwordBasicNameValuePAir = new BasicNameValuePair("paramPassword", paramPassword);

                // We add the content that we want to pass with the POST request to as name-value pairs
                //Now we put those sending details to an ArrayList with type safe of NameValuePair
                List<NameValuePair> nameValuePairList = new ArrayList<NameValuePair>();
                nameValuePairList.add(usernameBasicNameValuePair);
                nameValuePairList.add(passwordBasicNameValuePAir);

                try {
                    // UrlEncodedFormEntity is an entity composed of a list of url-encoded pairs. 
                    //This is typically useful while sending an HTTP POST request. 
                    UrlEncodedFormEntity urlEncodedFormEntity = new UrlEncodedFormEntity(nameValuePairList);

                    // setEntity() hands the entity (here it is urlEncodedFormEntity) to the request.
                    httpPost.setEntity(urlEncodedFormEntity);

                    try {
                        // HttpResponse is an interface just like HttpPost.
                        //Therefore we can't initialize them
                        HttpResponse httpResponse = httpClient.execute(httpPost);

                        // According to the JAVA API, InputStream constructor do nothing. 
                        //So we can't initialize InputStream although it is not an interface
                        InputStream inputStream = httpResponse.getEntity().getContent();

                        InputStreamReader inputStreamReader = new InputStreamReader(inputStream);

                        BufferedReader bufferedReader = new BufferedReader(inputStreamReader);

                        StringBuilder stringBuilder = new StringBuilder();

                        String bufferedStrChunk = null;

                        while((bufferedStrChunk = bufferedReader.readLine()) != null){
                            stringBuilder.append(bufferedStrChunk);
                        }

                        return stringBuilder.toString();

                    } catch (ClientProtocolException cpe) {
                        System.out.println("First Exception caz of HttpResponese :" + cpe);
                        cpe.printStackTrace();
                    } catch (IOException ioe) {
                        System.out.println("Second Exception caz of HttpResponse :" + ioe);
                        ioe.printStackTrace();
                    }

                } catch (UnsupportedEncodingException uee) {
                    System.out.println("An Exception given because of UrlEncodedFormEntity argument :" + uee);
                    uee.printStackTrace();
                }

                return null;
            }

            @Override
            protected void onPostExecute(String result) {
                super.onPostExecute(result);

                if(result.equals("working")){
                    Toast.makeText(getApplicationContext(), "HTTP POST is working...", Toast.LENGTH_LONG).show();
                }else{
                    Toast.makeText(getApplicationContext(), "Invalid POST req...", Toast.LENGTH_LONG).show();
                }
            }           
        }

        SendPostReqAsyncTask sendPostReqAsyncTask = new SendPostReqAsyncTask();
        sendPostReqAsyncTask.execute(givenUsername, givenPassword);     
    }
}