A secure OpenVidu sample app with a Java backend and a SPA frontend. It makes use of openvidu-java-client to get the necessary params from OpenVidu Server.

Understanding this example

OpenVidu is composed by the modules displayed on the image above.

openvidu-browser: JavaScript library for the browser. It allows you to manage your video-calls straight away from your clients
openvidu-java-client: Java package to easily get the necessary params (sessionId's and tokens) from openvidu-server. Quick alternative to REST API
openvidu-server: Java application that controls Kurento Media Server
Kurento Media Server: server that handles low level operations of media flow transmissions

You will only have to make use of openvidu-browser and openvidu-java-client to get this sample app working

Executing this example

Clone the repo:

git clone https://github.com/OpenVidu/openvidu-tutorials.git

You will need maven to build the project. You can install it with:
```
sudo apt-get install maven
```
To run the sample application, execute the following command in the project:
```
cd openvidu-js-java
mvn package exec:java
```
openvidu-server and Kurento Media Server must be up and running in your development machine. The easiest way is running this Docker container which wraps both of them (you will need Docker CE):
```
docker run -p 8443:8443 --rm -e KMS_STUN_IP=193.147.51.12 -e KMS_STUN_PORT=3478 -e openvidu.secret=MY_SECRET openvidu/openvidu-server-kms
```
Go to https://localhost:5000 to test the app once the server is running. The first time you use the docker container, an alert message will suggest you accept the self-signed certificate of openvidu-server when you first try to join a video-call.

Understanding the code

This is a very basic web application with a pretty simple vanilla JS/HTML/CSS frontend and a straightforward Java backend. OpenVidu assumes you can identify your users so you can tell which users can connect to which video-calls, and what role each one of them will have in them. You can do this as you prefer. Here our backend will manage the users and their sessions by using the non-intrusive HttpSession API. In these posts multiple options for user session management in Java are explained, inlcuding the one used in this tutorial: journaldev.com, studytonight.com.

Backend: SpringBoot app with the following classes (src/main/java path, io.openvidu.js.java package)
- App.java : entrypoint for the app
- LoginController.java : rest controller for handling login and logout operations
- SessionController.java : rest controller for getting sessionId's and tokens. It also stores our active video-calls and the users connected to them
Frontend: Pure JS/HTML/CSS files (src/main/resources/static)
- OpenVidu.js: openvidu-browser library. You don't have to manipulate this file.
- app.js: sample application main JavaScritp file, which makes use of OpenVidu.js.
- index.html: HTML code for the form to login, the form to connect to a video-call and for the video-call itself. It has two links to both JavaScript files:
```
<script src="OpenVidu.js"></script>
<script src="app.js"></script>
```
- style.css: some CSS classes to style index.html.

Let's describe the code following this scenario: a user logs in to the app and connects to the video-call "TUTORIAL", where he publishes his webcam. A second user will connect to the same video-call just after that and publish its own webcam. Both of them will leave the call after a while.

User logs in

We have implemented a method for making HTTP requests to the backend, as we will need to make at least three of them: one for logging in, one for getting the sessionId and a valid token from openvidu-server and a one for letting know our backend when any user leaves the video-call. The header of the method looks like this:

function httpRequest(method, url, body, errorMsg, callback)

Where method is whether "POST" or "GET", url the path of the REST operation, body the data to be passed, errorMsg the output error message if something goes wrong and callback the function to execute in case of success. As mentioned above, we need to call this method three times for each user that LOGS IN 🡒 CONNECTS TO A VIDEO-CALL 🡒 LEAVES THE VIDEO-CALL.

index.html will first show a form to log in:

app.js sends an HTTP request to "/api-login/login" passing the username and the password retrieved from the HTML form whenever "Log in" button is clicked:

function logIn() {
	var user = $("#user").val(); // Username
	var pass = $("#pass").val(); // Password
	var jsonBody = JSON.stringify({ // Body of POST request
		'user': user,
		'pass': pass
	});

	httpRequest('POST', '/api-login/login', jsonBody, 'Login WRONG',
	  function successCallback(response){ // Send POST request
		console.warn(userName + ' login');
		// HTML shows logged-in page ...
	});
}

LoginController.java checks the params are correct and if so sets an HttpSession for the newly logged user (adding a "loggedUser" attribute with its username in the HttpSession object):

@RequestMapping(value = "/api-login/login", method = RequestMethod.POST)
public ResponseEntity<Object> login(@RequestBody String userPass, HttpSession httpSession) 
					throws ParseException {

	// Retrieve params from POST body
	JSONObject userPassJson = (JSONObject) new JSONParser().parse(userPass);
	String user = (String) userPassJson.get("user");
	String pass = (String) userPassJson.get("pass");

	if (login(user, pass)){ // Correct user-pass
		// Validate session and return OK 
		// Value stored in HttpSession allows us to identify the user in future requests
		httpSession.setAttribute("loggedUser", user);
		return new ResponseEntity<>(HttpStatus.OK);
	} else { // Wrong user-pass
		// Invalidate session and return error
		httpSession.invalidate();
		return new ResponseEntity<>("User/Pass incorrect", HttpStatus.UNAUTHORIZED);
	}
}

User connects to "TUTORIAL" video-call

HTML will display now the user has logged in a different form, asking for the video-call to connect and the nickname the user wants to have in it. So our 'publisher1' user would write TUTORIAL in "Session" field and press "Join!" button:

app.js will execute joinSession() method, which starts like this:

function joinSession() {
	getSessionIdAndToken(function () { ...

So the first thing to do here is to retrieve a sessionId and a token from our backend. Only when we have them available in the browser we will continue with the join operation. Let's see what getSessionIdAndToken() looks like:

function getSessionIdAndToken(callback) {
	sessionName = $("#sessionName").val(); // Video-call to connect ("TUTORIAL")
	var jsonBody = JSON.stringify({ // Body of POST request
		'session': sessionName
	});

	// Send POST request
	httpRequest('POST', '/api-sessions/get-sessionid-token', jsonBody, 
	 'Request of SESSIONID and TOKEN gone WRONG:', function successCallback(response){
		sessionId = response[0]; // Get sessionId from response
		token = response[1]; // Get token from response
		callback(); // Continue the join operation
	});
}

Here is the second time we must call our httpRequest() method, sending the session we want to connect ("TUTORIAL") and waiting to get a sessionId and a token as response. The interesting part here is in SessionController.java. First of all there are some important attributes in this controller we must mention:

// OpenVidu object to ask openvidu-server for sessionId and token
private OpenVidu openVidu;

// Collection to pair session names and OpenVidu Session objects
private Map<String, Session> mapSessions = new ConcurrentHashMap<>();
// Collection to pair sessionId's and tokens (the inner Map pairs tokens and role associated)
private Map<String, Map<String, OpenViduRole>> mapSessionIdsTokens = new ConcurrentHashMap<>();

// URL where our OpenVidu server is listening
private String OPENVIDU_URL;
// Secret shared with our OpenVidu server
private String SECRET;

Rest controller method begins retrieving the param send by the client, which in this case is the video-call name ("TUTORIAL"), as well as preparing two params we will need a little further on: role and serverData.

@RequestMapping(value = "/api-sessions/get-sessionid-token", method = RequestMethod.POST)
public ResponseEntity<JSONObject> getSessionIdToken(@RequestBody String sessionNameParam, 
		HttpSession httpSession) throws ParseException {

	JSONObject sessionJSON = (JSONObject) new JSONParser().parse(sessionNameParam);

	// The video-call to connect ("TUTORIAL")
	String sessionName = (String) sessionJSON.get("session");

	// Role associated to this user
	OpenViduRole role = LoginController.users.get(httpSession.getAttribute("loggedUser")).role;

	// Optional data to be passed to other users when this user connects to the video-call
	// In this case, a JSON with the value we stored in the HttpSession object on login
	String serverData = "{\"serverData\": \"" + httpSession.getAttribute("loggedUser") + "\"}";

	JSONObject responseJson = new JSONObject();

Just after that an if-else statement comes into play: does the session "TUTORIAL" already exitsts?

if (this.mapSessions.get(sessionName) != null) { ...

In this case it doesn't because 'publisher1' is the first user connecting to it. So we focus on the else branch:

else {
	// New session: return a new sessionId and a new token
	try {

		// Create a new OpenVidu Session
		Session session = this.openVidu.createSession();
		// Get the sessionId
		String sessionId = session.getSessionId();
		// Generate a new token with the recently retrieved serverData and role
		String token = session.generateToken(new
			TokenOptions.Builder().data(serverData).role(role).build());

		// Store the session and the token in our collections
		this.mapSessions.put(sessionName, session);
		this.mapSessionIdsTokens.put(sessionId, new ConcurrentHashMap<>());
		this.mapSessionIdsTokens.get(sessionId).put(token, OpenViduRole.PUBLISHER);

		// Prepare the response with the sessionId and the token
		responseJson.put(0, sessionId);
		responseJson.put(1, token);

		// Return the response to the client
		return new ResponseEntity<>(responseJson, HttpStatus.OK);

	} catch (Exception e) {
		// If error generate an error message and return it to client
		return getErrorResponse(e);
	}
}

We are almost there! Now in app.js we can init a new Session with sessionId and connect to it with token:

// --- 1) Get an OpenVidu object and init a session with the retrieved sessionId ---

OV = new OpenVidu();
session = OV.initSession(sessionId);


// --- 2) Specify the actions when events take place ---

// On every new Stream received...
session.on('streamCreated', function (event) {

	// Subscribe to the Stream to receive it
	// HTML video will be appended to element with 'subscriber' id
	var subscriber = session.subscribe(event.stream, 'subscriber');

	// When the HTML video has been appended to DOM...
	subscriber.on('videoElementCreated', function (event) {

		// Add a new <p> element for the user's name and nickname just below its video
		appendUserData(event.element, subscriber.stream.connection);
	});
});

// On every Stream destroyed...
session.on('streamDestroyed', function (event) {
	// Delete the HTML element with the user's nickname
	removeUserData(event.stream.connection);
});


// --- 3) Connect to the session passing the retrieved token and some more data from
//         the client (in this case a JSON with the nickname chosen by the user) ---

session.connect(token, '{"clientData": "' + $("#participantName").val() + '"}', function (err) {

	// If the connection is successful, initialize a publisher and publish to the session
	if (!err) {

		// Here we check somehow if the user has at least 'PUBLISHER' role before
		// trying to publish its stream. Even if someone modified the client's code and
		// published the stream, it won't work if the token sent in Session.connect
		// method doesn't belong to a 'PUBLIHSER' role
		if (isPublisher()) {

			// --- 4) Get your own camera stream and publish it ---

			var publisher = OV.initPublisher('publisher', {
				audio: true,
				video: true,
				quality: 'MEDIUM'
			});


			// --- 5) Publish your stream ---

			session.publish(publisher);

		} else {
			console.warn('You don\'t have permissions to publish');
		}
	} else {
		console.warn('Error connecting to the session:', error.code, error.message);
	}

	// HTML shows session page ...

});

The user will now see its own video on the page. The connection to the session has completed!

Another user connects to the video-call The process would be exactly the same as before until SessionController.java executes getSessionIdAndToken() method. Now session 'TUTORIAL' already exists, so in the if-else statement the if branch would be the one executed:

if (this.mapSessions.get(sessionName) != null) {
	// Session already exists: return existing sessionId and a new token
	try {

		// Get the existing sessionId from our collection with 
		// the sessionName param ("TUTORIAL")
		String sessionId = this.mapSessions.get(sessionName).getSessionId();
		// Generate a new token with the recently retrieved serverData and role
		String token = this.mapSessions.get(sessionName)
		.generateToken(new
			TokenOptions.Builder().data(serverData).role(role).build());

		// Update our collection storing the new token
		this.mapSessionIdsTokens.get(sessionId).put(token, OpenViduRole.PUBLISHER);

		// Prepare the response with the sessionId and the token
		responseJson.put(0, sessionId);
		responseJson.put(1, token);

		// Return the response to the client
		return new ResponseEntity<>(responseJson, HttpStatus.OK);

	} catch (Exception e) {
		// If error generate an error message and return it to client
		return getErrorResponse(e);
	}
}

The code executed in app.js would be also the same. After the Session.publish() method has been succesful, both users will be seeing each other's video, as well as the username and the nickname below it.

Users leave the video-call

After a while both users decide to leave the session. Here is where the last HTTP operation takes place: we must let the backend know that certain user has left the session so it can update the collections with the active sessions and tokens. In app.js we run the following HTTP POST operation:

function removeUser() {
	// Body of POST request with the name of the session and the token of the leaving user
	var jsonBody = JSON.stringify({
		'sessionName': sessionName,
		'token': token
	});

	// Send POST request
	httpRequest('POST', '/api-sessions/remove-user', jsonBody,
		'User couldn\'t be removed from session', function successCallback(response) {
		console.warn(userName + ' correctly removed from session ' + sessionName);
	});
}

And in SessionController.java we update the collections:

@RequestMapping(value = "/api-sessions/remove-user", method = RequestMethod.POST)
public ResponseEntity<JSONObject> removeUser(@RequestBody String sessionNameToken, 
	HttpSession httpSession) throws Exception {

	// Retrieve the params from BODY
	JSONObject sessionNameTokenJSON = (JSONObject) new JSONParser().parse(sessionNameToken);
	String sessionName = (String) sessionNameTokenJSON.get("sessionName");
	String token = (String) sessionNameTokenJSON.get("token");

	// If the session exists ("TUTORIAL" in this case)
	if (this.mapSessions.get(sessionName) != null) {
		String sessionId = this.mapSessions.get(sessionName).getSessionId();

		if (this.mapSessionIdsTokens.containsKey(sessionId)) {
			// If the token exists
			if (this.mapSessionIdsTokens.get(sessionId).remove(token) != null) {
				// Token has been removed
				if (this.mapSessionIdsTokens.get(sessionId).isEmpty()) {
					// Last user left: session "TUTORIAL" must be removed
					this.mapSessions.remove(sessionName);
				}
				return new ResponseEntity<>(HttpStatus.OK);
			} else {
				// The TOKEN wasn't valid
				return new ResponseEntity<>(HttpStatus.INTERNAL_SERVER_ERROR);
			}
		} else {
			// The SESSIONID wasn't valid
			return new ResponseEntity<>(HttpStatus.INTERNAL_SERVER_ERROR);
		}
	} else {
		// The SESSION does not exist
		return new ResponseEntity<>(HttpStatus.INTERNAL_SERVER_ERROR);
	}
}

When the last user leaves the session this.mapSessions.remove(sessionName); will be executed: this means the session is empty and that it is going to be closed. The sessionId and all token params associated to it will be invalidated.

At this point we have covered all the important code from the tutorial. With this scenario we have seen the most common use-case, but you can modify whatever you want to suit your needs. And remember that this is one single approach, using certain technologies: you can implement your frontend and your backend as you want. The only actual requirements are getting sessionId and token params from openvidu-server and using them along with openvidu-browser to connect your clients to the sessions.