A short presentation on WebSockets and their Java server-side usage.

1. WebSocket
Bozhidar Bozhanov
...one day at home I decided I'm bored => a
WebSocket-based game for
http://computoser.com

2. Usecases
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Games
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Stock-exchange application
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...anything, really

3. Why WebSocket?
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Push
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Real-time communication
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Resource-light
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Intuitive, non-hacky

4. Up to now
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Ajax polling (a.k.a. "are we there yet?")
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Long-polling, streaming
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Plugins – flash/applets/ActiveX
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Problems: hacky, resource-heavy, serverthread-unfriendly

5. WebSocket
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Standard (HTML5)
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TCP, full-duplex
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More effective on the server-side
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High-level protocols ontop – STOMP, WAMP,
etc.

6. Client-side
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Standard JavaScript API
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Browser support – problematic
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SockJS, socket.io, fallbacks

7. Server-side
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node.js
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Java – Java EE WebSocket API (JSR-356)
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Servlet container implementations – thread
pools
Spring-MVC API, Spring Messaging API

8. Java WebSocket API vs Spring
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Very similar
One handler per endpoint, differentiate based
on payload
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Out-of-the-box dependency injection with spring
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No annotation configuration in spring (yet)

9. Messaging
●
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Alternative architecture
Using a message broker
(simple/ActiveMQ/RabbitMQ/..) behind spring
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STOMP over WebSocket
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Client subscribes for events

10. DDD and TDD
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DDD comes naturally
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Objects and their workflows are easily testable
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Very few mocks, comparable to spring-mvc
@RequestMappings

11. Security and authentication
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WSS vs WS (ws://example.com/game)
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No same-origin policy. Origin header.
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Validate input and output
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Authentication – cookies? Cookie-like workflow.

12. Conclusion
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It's cool :)