Thursday, January 21, 2016

Stream Encrypted Video with Windows Azure Media Services

After a massive break I thought to write on the topic since there are lack of resources. I'm streaming my AES encrypted video with JWT authentication and generating the auth token with Java. If you have Azure Media Service enabled account you are welcome to try this out :).

Following are couple of useful resources in the web for testing this process.

JWT official site and token verification tool -
Azure media player -
Base64URL encoder -
HMAC generator -

At first we need to have encrypted videos uploaded to our Azure account. Following are the steps to doing that.
1. Login to
2. Go inside your media service account
3. Click on Upload a video file link under Managemant Tasks section (or else click on Content tab and then click on Upload Content link) and upload a video file.
4. Click on Process icon at the bottom, and click OK with default values.
5. Click on Sync Metadata icon at the bottom (Probably this will take some time)
6. Click on Encryption > Enable AES Encryption (If the Encryption icon not yet enable, logout and login again and try. It may take some time to enable that)
7. Click on Publish icon (SS for 4-7

Now you can copy the encrypted video publish URL which will be like :

Then go to Content Protection tab and set up the necessary attributes like this SS and click on manage verification keys button and regenerate primary key. And don't forget to save :)

For streaming the above encrypted video, we need to create a JWT auth token which is the tricky part. Following is sample java code to generate the token.

package azurejwttoken;

import java.util.logging.Level;
import java.util.logging.Logger;
import javax.crypto.Mac;
import javax.crypto.spec.SecretKeySpec;
import org.apache.commons.codec.binary.Base64;

 * @author chanaka
public class AzureJWTToken

     * @param args the command line arguments
    public static void main(String[] args)
        // Use the Primary Verification Key which you regenerated
        String          secret              = "YEAIfGy6cIXy1xhcIdgEoBfiWNoI3zq2FCKVQhdZXMcHGN+BAwicafgbRscsVZj1Us3RlWihphY1XMBuQOhlBg==";
        long            validitymillis      = 15 * 60 * 1000; // 15 minutes
        long            nowMillis           = System.currentTimeMillis();
        long            expireSeconds       = (nowMillis + validitymillis) / 1000; // Use seconds instead milli seconds
        String          jsonHeaderString    = "{\"typ\":\"JWT\",\"alg\":\"HS256\"}";
        // Use your ISSUER and SCOPE attributes properly here
        String          jsonBodyString      = "{\"iss\":\"\",\"aud\":\"urn:jwttest\",\"exp\":" + expireSeconds + "}";
        String          token               = getAuthToken(secret, jsonHeaderString, jsonBodyString);
        System.out.println("Token : " + token);
    public static String getAuthToken(String secret, String jsonHeaderString, String jsonBodyString)
        String          token       = null;
            Mac             sha256_HMAC         = Mac.getInstance("HmacSHA256");
            SecretKeySpec   secret_key          = new SecretKeySpec(Base64.decodeBase64(secret), "HmacSHA256");
            String          content             = Base64.encodeBase64URLSafeString(jsonHeaderString.getBytes()) + "." + Base64.encodeBase64URLSafeString(jsonBodyString.getBytes());
            String          hash                = Base64.encodeBase64URLSafeString(sha256_HMAC.doFinal(content.getBytes()));
            token           = "Bearer%3D" + content + "." + hash;
        catch (NoSuchAlgorithmException ex)
            Logger.getLogger(AzureJWTToken.class.getName()).log(Level.SEVERE, "Error occured while generating AuthToken : NoSuchAlgorithmException", ex);
        catch (InvalidKeyException ex)
            Logger.getLogger(AzureJWTToken.class.getName()).log(Level.SEVERE, "Error occured while generating AuthToken : InvalidKeyException", ex);
        catch (Exception ex)
            Logger.getLogger(AzureJWTToken.class.getName()).log(Level.SEVERE, "Error occured while generating AuthToken", ex);
        return token;
     * In case you need to convert base64 string to URL safe manually ()
     * @param base64EncodedString
     * @return 
    public static String replaceUrlSafeChars(String base64EncodedString)
        base64EncodedString = base64EncodedString.replace('+', '-');
        base64EncodedString = base64EncodedString.replace('/', '_');
        base64EncodedString = base64EncodedString.replace("=", "");
        return base64EncodedString;

Using the JWT site we can verify the generated auth token. Just paste your token to JWT Debugger without the "Bearer%3D" part like this SS.

If it's correct you should be able to play it with Azure media player like this SS. Note that token will expire after 15 minutes according to our code. You can increase that accordingly.

Finally you can stream your video with following hard coded HTML source. Make sure you open the HTML with web server.

<!DOCTYPE html>
        <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
  <iframe src="//" name="azuremediaplayer" scrolling="no" frameborder="no" align="center" height="280px" width="500px" allowfullscreen></iframe>    </body>
Iframe src dynamic url parameter :
    url : URL encoded encrypted video URL -, "UTF-8")
    token : The token generated from the java code

Hope you enjoy. Happy coding... :)

I like to thank Saliya Randunu for providing me lots of resources :)

Wednesday, April 9, 2014

Getting Started with WSO2 ESB Connectors

Enterprise Service Bus (ESB) is the infrastructure which provides the implementation of the concept of Service Oriented Architecture (SOA). The connectors are the new concept coming with the wso2 ESB version 4.8.0 and above. Connector is an intermediate API layer, which will represent a real world developer API, while being in the ESB itself. With this post, the initial steps to create a connector will be described.

Download Maven Dependencies:
You need to checkout the source code from here and run maven install command on it. It will download set of required dependencies to your local maven repository. Following are the commands if you have a command line SVN and maven client.

$svn co
$cd org.wso2.carbon.connector/
$mvn clean install

Generate Connector Folder Structure:
Run the following maven command to generate maven project sample connector code.

$mvn archetype:generate -DarchetypeGroupId=org.wso2.carbon -DarchetypeArtifactId=org.wso2.carbon.mediation.library.connectors.connector-archetype -DarchetypeVersion=4.2.0 -DgroupId=org.wso2.carbon.connector -DartifactId=org.wso2.carbon.connector -Dversion=4.2.0

You may need give a name for the connector while processing the above process. (Let's proceed with entering googlebooks as connector name.) If the project creation success, you are ready to develop a connector with the following directory structure.

Fig. 1 : Connector Directory Structure

Before developing, there are some main components which you need to know.

Synapse Template : This is the component which calling to actual end point with the given request data. This will be placed in resources directory.

Proxy : This will handle the request coming inside to the ESB and response coming from the actual end point. This is not a part of connector, but need to invoke the connector.

Request : The request which follows the API published from the connector. This request can be REST or SOAP.

Connector for which API ?
There are large number of services which is provide in the world wide web to do a specific functions. In order to use these for developers, there will be one or several web service APIs  like REST, SOAP or a client libraries in one or several languages are provided by the service provider. Out of these, REST will be the simplest one that others since it has less work. Here we are using Google Book REST API which does not need authentication for some of services like volume search.

First we'll go the Google Books REST API documentation and identify the categorization of the services in GoogleBooks API. The services are categories like Bookshelf, Volume, Bookshelf.volumes etc. So we'll create new directory "volume" under resources directory, to place services in the Volume category.

Writing Synapse Template :
You can have a look on the sample Synapse template generated at helloWorld directory. Following synapse template is providing the service at list volume. This should be placed under "volume" directory as listVolume.xml.

<template name="listVolume" xmlns="">
    <parameter name="searchQuery" description="Full-text search query string." />
      <property name="uri.var.searchQuery" expression="$func:searchQuery" />
                <http method="get"
uri-template="{uri.var.searchQuery}" />

Create a component.xml file in "volume" directory, with following content.

<?xml version="1.0" encoding="UTF-8"?>
<component name="googlebooks_volume" type="synapse/template">
        <component name="listVolume">
            <description>List volumes matching for the given query.</description>

Modify the conector.xml file by adding new dependency as below,

<?xml version="1.0" encoding="UTF-8"?>
    <component name="googlebooks" package="org.wso2.carbon.connector" >
         <dependency component="helloWorld"/>
         <dependency component="googlebooks_volume"/>
         <description>wso2 sample connector library</description>

Now you can build the connector code and test the implemented service foe volume search method. To build the connector, run maven clean install command from the org.wso2.carbon.connector directory.

$mvn clean install

This will generate file in the target directory. You can upload this zip file through the ESB interface under connector category. Make sure you enabled the connector after uploading.

Writing Proxy :
Now you can invoke the implemented service for search volumes, by writing a proxy through ESB server interface. (Home>Manage>Services>Add>Proxy Service>Custom Proxy>switch to source view)

<?xml version="1.0" encoding="UTF-8"?>
<proxy xmlns=""
         <property name="searchQuery" expression="json-eval($.searchQuery)"/>

Request :
Using a REST client, send following request, (you can use POSTMAN)

POST /services/googlebooks_listVolume HTTP/1.1

Hope you get the correct response ;)

Thursday, November 21, 2013

OAuth2 with LinkedIn

OAuth2 basically allows third party application, to access protected resource of a specific user. You may have seen some web applications/sites allows you to login through your Google, Facebook, LinkedIn etc accounts. As an example just try this with any mentioned account (Google, Facebook, Yahoo etc.). After giving your username password credentials you will be notified the authorities which the third party application will get if you agreed to proceed.

Some important term definitions in OAuth2:
  • Resource Owner - The person/entity which capable of granting the access to a protected resource.
  • Resource Server - The server which contains the protected resources, and capable of deal with access tokens in protected resource requests.
  • Client - The application which requests for protected resources on behalf of resource owner.
  • Authorization Server - The server which authorize resource owner, and issue access tokens to the client

Following figure shows basic flow of OAuth2 authentication process.

If you are really interested in digging more details, OAuth2 RFC will be the best resource. I strongly recommend you to go through at least up to 1.6 section in the RFC.

With this blog post, I show you how third party java application can access protected LinkedIn resources.

1. Register an application on LinkedIn. - This basically helps to create a link between LinkedIn and your application (third party application).

2. Get an access token - The access token represent the credentials to access protected resources. So your application does not need to store resource owner's credentials, but the access token.

3. Make API calls - Yes, after obtaining access token you are free to call API methods with that, until it expires.

LinkedIn official documentation contains detailed description on the above steps. You can follow those and familiar with this matter. Make sure you tried both Authorization code request and Access token request.

Now we need our application to store access token. For this we have to do some coding in the application. We can easily get authorization code with a GET request. Then we need a POST request to get access token using the authorization code and other required parameters.

So, we can get the authorization code from request parameters in the redirect uri, and make server side code request to get the access token. For this we have to use a HTTP client library. You can use Apache HTTP client library components to approach this. For process the responce you can use XML parser like DOM or SAX. Try out the sample application yourself after reaing README file. Happy coding !

Thanks to mkyong for making me comfortable with his SpingMVC example.

Tuesday, January 8, 2013

Limit textarea character count in IE8

   After long time I'm going to start blogging again. Yes, it's on your favorite browser IE :). As you know, with HTML 5 there is lots of additional features support for major browsers except IE. However it's nice to hear that IE10 is having more support for HTML 5.

     With the HTML 5, maxlength attribute was introduced for textarea HTML element. But IE 8 does not have support for this. I did some work around to find a simple solution for this and seems I found it.

    Make sure you are using HTML 5 doctype. Note that I have target only IE here, but not the already support browser for maxlength attribute in teaxtarea elements.

    <script type="text/javascript">
      function getCaret(el) {
        if (el.selectionStart) {
          return el.selectionStart;
        } else if (document.selection) {
          var r = document.selection.createRange();
          if (r == null) {
            return 0;
          var re = el.createTextRange(),
          rc = re.duplicate();
          rc.setEndPoint('EndToStart', re);
          return rc.text.length;
        return 0;
      function limitPasteData(obj, limit) {
        // Do it with Internet Explorer
        if (window.clipboardData) {
          if (document.selection && document.selection.createRange) {
            var modifiedTxtLen;
            // If text has been selected
            if (document.selection.createRange().text.length > 0) {
              modifiedTxtLen = obj.value.length - document.selection.createRange().text.length + window.clipboardData.getData("Text").length;
              if (modifiedTxtLen > limit) {
                var neededLen = limit - (obj.value.length - document.selection.createRange().text.length);
                document.selection.createRange().text = window.clipboardData.getData("Text").substring(0, neededLen);
                return false;
            } else {
              modifiedTxtLen = obj.value.length + window.clipboardData.getData("Text").length;
              if (modifiedTxtLen > limit) {
                var neededLen = limit - obj.value.length;
                var neededTxt = window.clipboardData.getData("Text").substring(0, neededLen);
                var mofifiedText = obj.value.substring(0, getCaret(obj)) + neededTxt + obj.value.substring(getCaret(obj), obj.value.length);
                obj.value = mofifiedText;
                return false;
            // If not exceed limit just paste it
            return true;
      function limitTypingData(obj, limit) {
        // Other browsers may have support for maxlength attribute
        if (navigator.appName == 'Microsoft Internet Explorer') {
          if (obj.value.length > (limit - 1)) {
            if (document.selection && document.selection.createRange) {
              // If only text has been selected, allow to type once
              if (document.selection.createRange().text.length > 0) {
                return true;
            return false;
    <textarea id="txtArea" cols="20" rows="5" maxlength="15"
        onpaste="return limitPasteData(this, 15);"
        onkeypress="return limitTypingData(this, 15);" ></textarea>

       But remember that the behavior of these functions in IE8 will not 100% equal to default maxlength behavior of supporting browsers. But we can still do the work with this.

Apart from that I would like to notice you that, new line character(s) may be changed in IE than others. IE always take it as '\n\r' and other browsers may take it as '\n'. So that, either you have to handle that or use additional space from the back end database fields.

Have a fun with IE 8 :D

Thursday, September 6, 2012

Code to interfaces, not to implementations

      In object oriented programming, interfaces are commonly used to implement more flexible software. Interfaces are very useful to extend and improve  a software application. While designing a software its a good practice to use interfaces where applicable.

           Lets think about a simple CricketPlayer class (Figure 1) with a method play(). There can be several classes and methods using CricketPlayer class. Think we need to give the support for Football player as well within this software. Then we need to repeat the wheel for new purpose(Figure 2).

Figure 1 : Initial cricket class

Figure 2 :Modification for support football player

        But just think if we use common interface (Figure 3) for any type of player, we can easily get rid of the problem. Player interface will have play() method which may be different behaviour for different players and getSport() method which represent the type of the player (sport). CricketPlayer and FootballPlayer subclasses can implement their own behaviours according to related declarations in the Player interface. Coding to this interface will save us with very limited changes, while any kind of player class is going to use in our software. Using an interface software can be extend easily and will be more generic.

Figure 3 : Player interface

        Recently I saw practically very useful place where interfaces are using. Most of the industry applications are using the MVC architecture to better maintainability of the code. There may have requirements to use the same applications with different DBMS for different clients. Using an interface with n-tier architecture, this support can be easily implemented.

          Following diagram (Figure 4) shows the way of using this stratergy in n-tier architectural application. From the Controller classes which deals with request and responses while dealing with the business logic of the application, calls to the service classes to do specific data manipulation, transaction etc. Service classes calls to Dao classes which deals with data transactions. Service class doesn't directly use either MySqlUserDoa which has MySQL support or XQueryUserDoa which has XQuery support. It only care about BaseUserDao interface, and doesn't care about real object underling the BaseUserDao interface.

Figure 4 : Dao interface

      Implementaion under this process is quite simple. Control class read configuration file (or from any other way) and get the Query Language supposed to use according to the requierments. Then create an object of supported Dao class and assigned to a variable of BaseUserDao (interface) type. After this initializing process of BaseUserDao type variable, it can be used by the service classes inside their functions.

BaseUserDao userDao;
if (queryLanguage == 'MySQL') {
    userDao = new MySqlUserDao();
} else if (queryLanguage == 'XQuery') {
    userDao = new XQueryUserDao();

        Since application is not creating concrete classes (objects are dynamically created in run time and will not directly creating objects for any case), it will not be limited. And since it uses an interface, switching for a new DBMS can be achieved by only adding new file which inherit the interface and modify the object creating process(modify above code) and giving the new DBMS as parameter, using a configuration file or any other way.

      Coding to interfaces, not to implementations principle is a good practice for a good software and it make our work more easy. If you are thinkng of creating extendable software application, this practice will very helpful. So, its time to play with interfaces. :)

Tuesday, August 28, 2012

Singleton with PHP

        Singleton pattern is under creational design patterns which deals with mechanisms of creating objects according to the situation. I recently used this pattern with PHP. It's very important to get to know use of this pattern.

              Singleton pattern can be used for always keep one object of a specific class while an application is running. It save the memory which is going to allocate for new objects of the class in every where inside the application. Singleton practically used for logger classes which provide global logging access point whithout logging each and every application after the main loggin operation, configuration classes which consist configuration data of an application, access resources which are in shared mode like multi threading applications, Factory design pattern which dynamically create the objects etc.

         It's very easy to implement singleton with PHP (as well as other languages). What we need to do is make a private constructor and control the creating object of this class by a public method. Following code snippet shows how to do this.

class MySingleton {

    private static $instance = null;

    public static function getInstance() {
        if(is_null($this->instance)) {
            $this->instance = new MySingleton($params);
        return $this->instance;

    private function __construct($params) {
        // set parameters

    public function doSomething() {
        // some code


         Since the constructor is private only the class itself can be access the constructor. getInstance method is accessible for anywhere and since that is a static method it can be used anywhere without creating an object of this class. This function handles the situations of the need of a new instance of MySingleton class by calling the private constructor if needed. Static variable is used because of the restriction of using non-static fields inside static functions.

In the places where needs to call doSomething method in MySingleton class, we call as,
or, if the functions inside the class is frequently used,
$my_singleton = MySingleton::getInstance();
$my_singleton ->doSomething()

It's very simple. Hope this helpful. Have a fun with singleton. :)

Saturday, August 25, 2012

සැරයටියෙනුත් යනෙනා තුරා.....

කෙලිලොලෙන් ගතකරපු අපේ ඒ අතීතය.....
මතකයක් පමණක්ම කර,
ඇයිද නුඹ අපව තනිකර ගිලිහුණේ.....

ඒ අතීතය,
හැමදාමත් අද ඊයේ වගේ දැනේවි,
නුඹේ කතා කනට ඇසේවි,
නුඹේ සිනහව හිතේ මැවේවි,

නුඹේ කතාව, ඒ සිනහව
මතු කිසිදිනෙක අප හැබැහින්ම නොවිදීවි.....

නුඹ දමා ගියත් අපව,
මිතුරෙකුව හදේ රැදී සිටී හැම දිනෙක.....

මතු භවයෙදිත් අප මිතුදමින් බැදෙමු
මෙලෙස අකාලයේ ලොවම හැර දමා යන්නට නොව,
සැරයටියෙනුත් ගමන් කරනා තෙක්ම.....