Spring can integrate with WebSockets to enable asynchronous data exchange between a client and server. This overcomes limitations of synchronous HTTP. WebSockets provide a persistent connection and low overhead compared to alternatives like polling. Spring supports WebSocket through STOMP, a messaging subprotocol. It allows configuration of WebSocket endpoints in Spring MVC. However, the internal Spring architecture is not optimal if an external message broker is involved rather than using Spring's embedded broker.

1. Spring + WebSocket integration
SEMENOV OLEKSANDR

2. Agenda
1) The problem of synchronous data exchange model
2) Existing solutions
3) WebSocket
4) Subprotocols: STOMP
5) Spring MVC + WebSocket architecture
6) Drawbacks
7) Showcase

3. The problem
HTTP is synchronous, but sometimes asynchronous data receiving from
server is required

4. The problem

5. Existing solutions
Several ways to solve it:
1) Polling
2) Long polling
3) Endless iframe
4) HTML5: Server Side Events
5) HTML5: WebSocket

6. Polling

7. Long polling

8. Polling/long polling. Drawbacks
Self-initiated DDoS attack!

9. Polling/long polling. Drawbacks
1) Network overhead
a) SSL handshake can be initiated each time, and it is expensive
2) User presence tracking is complicated
3) In case of load balancer, each time user will be connected to
different server

10. Server Side Events

11. Server Side Events. API

12. Server Side Events. Drawbacks
Browser support is limited

13. Any alternatives?

14. WebSocket

15. WebSocket features
1) Bidirectional
2) Binary
3) No data overhead
4) Persistent connection
5) Supported by most proxies and load-balancers

16. WebSocket handshake

17. WebSocket handshake

18. WebSocket advantages

19. WebSocket vs REST approach
REST
1) Each URL mapped to resource
2) Each HTTP method has predefined semantics
WebSocket
1) Single URL for handshake
2) No predefined semantics

20. What does it mean?
Communications via WebSocket is much closer
to messaging approach*
But no concrete messaging protocols are defined

21. WebSocket subprotocols
1) WAMP – provides RPC + messaging features.
2) STOMP – provides messaging features only. Can be easily integrated
with message brokers like ActiveMQ, RabbitMQ etc.
3) 20+ other subprotocols

22. STOMP

23. Integration with Spring MVC
Client side
1) stomp.js library
Server side
1) Spring 4+

24. Client-side configuration

25. Server-side configuration

26. Server-side configuration

27. Other features
1) Exception handling
2) Flexible destinations
3) External message broker pluging-in

28. Internal architecture

29. External broker case

30. Drawbacks
What if you want connect directly to external message
broker and put message there, not via WebSocket endpoint?

31. It is impossible with current Spring architecture. Workarounds required.

32. Conclusions
1) WebSocket is standardized technology for bidirectional data
exchange in web.
2) WebSocket is fast and low latency
3) Spring 4+ easily integrates with websockets using STOMP
subprotocol.
4) Spring 4+ internal architecture is not ideal

33. Thank you!