Java EE 7 Websocket

1. Full Duplex Communication in Java EE 7
07 juli 2016
Masudul Haque

2. “Limitation” of HTTP
• Client-driven
• Half-duplex
• Verbose
• NewTCP connection
• Hacks for server push
- Polling
- Long Polling
- Comet/Ajax
- complex, insufficient, wasteful.

3. “Limitation” of HTTP

4. “Limitation” of HTTP

5. How WebSocket solves it ?
• Bi-directional (client-driven)
• Full-duplex (half-duplex)
• Lean protocol (verbose)
• SingleTCP connection (newTCP)

6. What is WebSocket?
• Bi-directional, full-duplex, communication channel
over a single TCP connection
• Originally proposed as part of HTML5
• IETF-defined Protocol: RFC 6455
• W3C-defined JavaScript API

7. Half vs Full Duplex

8. How does it work?
• Upgrade HTTP to WebSocket (single TCP connection)
• Send dataframes in both direction (bi-directional)
• Send messages independent of each other (full-
duplex)
• End the connection

9. How does it work?
Client Server
Handshake Request
Handshake Response

10. Handshake Request
GET /chat HTTP/1.1
Host: server.example.com
Upgrade: websocket
Connection: Upgrade
Origin: http://example.com
Sec-WebSocket-Key: dGhlIHNhbXBsZSBub25jZQ==
Sec-WebSocket-Protocol: chat, superchat
Sec-WebSocket-Version: 13

11. Handshake Request
GET /chat HTTP/1.1
Host: server.example.com
Origin: http://example.com
Sec-WebSocket-Key: dGhlIHNhbXBsZSBub25jZQ==
Sec-WebSocket-Protocol: chat, superchat
Sec-WebSocket-Version: 13
Upgrade: websocket
Connection: Upgrade

12. Handshake Response
HTTP/1.1 101 Switching Protocols
Upgrade: websocket
Connection: Upgrade
Sec-WebSocket-Accept: s3pPLMBiTxaQ9kYGzzhZRbK+xOo=
Sec-WebSocket-Protocol: chat

13. How does it work?
Client Server
Websocket
Handshake Request
Handshake Response

14. How does it work?
Peer
(Client)
Peer
(Server)
Websocket
Handshake Request
Handshake Response

15. How does it work?
Peer
(Client)
Peer
(Server)
Websocket
onOpen onOpen
onMessage
onMessage
onMessage
onMessage
Closing Handshake and Disconnected
onMessage

18. Http vs WebSocket

19. Java API WebSocket support
• API forWebSocket server and client endpoint
• Annotated: @ServerEndpoint,@ClientEndpoint
• Programmatic:Endpoint
• WebSocket opening handshake negotiation
• Lifecycle Callback methods
• Integration with Java EE technologies

20. Java API WebSocket support
Method-level annotations
• @OnMessage: Intercepts WebSocket messages
• @OnOpen: Intercepts WebSocket open events
• @OnClose: Intercepts WebSocket close events
• @OnError: Intercepts WebSocket error events

21. Java API WebSocket support
@ServerEndpoint("/chat")
public class ChatEndpoint {
@OnMessage
public void message(String message, Session client) throws IOException, EncodeException {
System.out.println("message: " + message);
for (Session peer : client.getOpenSessions()) {
peer.getBasicRemote().sendText(message);
}
}
}

22. Encoder & Decoder
Decoder = text message -> Java object
Encoder = Java object -> text message
• Often, XML or JSON is used as

23. Encoder & Decoder
@ServerEndpoint(value = "/websocket",
encoders = { FigureEncoder.class },
decoders = { FigureDecoder.class })
public class Whiteboard {
….
public class FigureEncoder implements Encoder.Text<Figure> {
@Override
public String encode(Figure figure) throws EncodeException {
return figure.getJson().toString();
}
}
public class FigureDecoder implements Decoder.Text<Figure> {
@Override
public Figure decode(String string) throws DecodeException {
JsonObject jsonObject = Json.createReader(new StringReader(string)).readObject();
return new Figure(jsonObject);
}

24. Demo

25. Q & A

26. Contact
For any question
Email: M.Haque@cimsolutions.nl
Follow me in following site:
Stackoverflow
http://stackoverflow.com/users/1265660/masud
Github
https://github.com/masudcse05
Blog
https://masudulhaque.wordpress.com