A modern web browser supports a surprising number of protocols designed for fast, efficient, and secure communication. Even though some goals of these protocols might overlap, their features are different enough to make them all worth our attention. This session focuses on HTTP/2, SSE, and WebSocket. It is based on experience gained during development of popular Jersey and Tyrus libraries. It explains all mentioned protocols and compares them, in both theory and practice, using java-based examples. Youtube: https://www.youtube.com/watch?v=G4V3b_z5TVk

3. Copyright © 2016, Oracle and/or its affiliates. All rights reserved. |
Web protocols for Java
Developers
Pavel Bucek
Oracle
September, 2016
CON4156

4. Copyright © 2016, Oracle and/or its affiliates. All rights reserved. |
Safe Harbor Statement
The preceding is intended to outline our general product direcLon. It is intended for
informaLon purposes only, and may not be incorporated into any contract. It is not a
commitment to deliver any material, code, or funcLonality, and should not be relied upon
in making purchasing decisions. The development, release, and Lming of any features or
funcLonality described for Oracle’s products remains at the sole discreLon of Oracle.
4

5. Copyright © 2016, Oracle and/or its affiliates. All rights reserved. |
Program Agenda
EvoluLon – HTTP and rest REST
Polling, Long Polling
SSE, WebSocket
HTTP/2
Demo, Q&A
1
2
3
4
5
5

6. Copyright © 2016, Oracle and/or its affiliates. All rights reserved. |
EvoluLon – HTTP
• HTTP V0.9 (1991)
– First version proposed by Tim Berners-Lee from CERN
– Only GET method, server returned HTML
– W3C standard
– Fun to read, whole standard is a single page
hbps://www.w3.org/Protocols/HTTP/AsImplemented.html
• Dave Raggeb – leader of the HTTP Working Group – expanding protocol
with more operaLons, meta-informaLon, security, ..
• HTTP V1.0 introduced in 1995 – RFC 1945
Hypertext Transfer Protocol
6

7. Copyright © 2016, Oracle and/or its affiliates. All rights reserved. |
EvoluLon – HTTP
• HTTP Working Group published HTTP/1.1 as “pre-standard”
• Rapid adopLon by servers and browsers
– (Arena, Netscape, Mosaic, Lynx, Internet Explorer)
• HTTP/1.1 finalized in 1997 (RFC 2068), improved in 1999 (RFC 2616)
• 2007 - HTTPbis Working group formed to revise and clarify the spec
– RFC 7230 – Message Syntax and RouLng, 7231 – SemanLcs and Content, 7232 –
CondiLonal Requests, 7233 – Range Requests, 7234 - Caching, 7235 – AuthenLcaLon
• HTTP/2 – May 2015 – RFC 7540
Hypertext Transfer Protocol
7

8. Copyright © 2016, Oracle and/or its affiliates. All rights reserved. |
Hypertext Transfer Protocol
8
REQUEST
GET /en/ HTTP/1.1
Host: www.java.com
User-Agent: curl/7.43.0
Accept: */*
<CR><LF><CR><LF>
RESPONSE
HTTP/1.1 200 OK
Server: Oracle-ApplicaLon-Server-11g
Last-Modified: Thu, 31 Mar 2016 22:48:16 GMT
device_type: Any
host_service: FutureTenseContentServer:11.1.1.8.0
X-Powered-By: Servlet/2.5 JSP/2.1
Content-Type: text/html; charset=UTF-8
Content-Language: en
X-Frame-OpLons: SAMEORIGIN
Content-Length: 7516
Date: Mon, 05 Sep 2016 20:22:35 GMT
ConnecLon: keep-alive
Vary: User-Agent
... Content <CR><LF><CR><LF>

9. Copyright © 2016, Oracle and/or its affiliates. All rights reserved. |
EvoluLon – REST
• Basic sovware architecture / scheme
• Exposes Resources (URIs), which handle METHODs
– GET/PUT/POST/DELETE/HEAD/OPTIONS/TRACE/PATCH/…
• MediaType (Accept/Content-Type)
– text/plain, text/html, applicaLon/json, …
• Caching (GET, HEAD), Hyperlinking, …
Representa@onal State Transfer
9

10. Copyright © 2016, Oracle and/or its affiliates. All rights reserved. |
EvoluLon – REST
Representa@onal State Transfer
10
Client Server
GET /hello HTTP/1.1
Header: value
…
HTTP/1.1 200 OK
Header: value
…
<enLty>

11. Copyright © 2016, Oracle and/or its affiliates. All rights reserved. |
Java API for RESTful Web Services (JAX-RS)
• JSR 311 – JAX-RS 1.1 – Java EE 6
– Server side REST Resources
– @Path, @GET, @POST, @Produces, @Consumes, @QueryParam, @Context, …
• JSR 399 – JAX-RS 2.0 – Java EE 7
– Client API, Filters and Interceptors, Async processing, integraLon with other EE specs
• JAX-RS 2.1 – Java EE 8
– Non-blocking IO, ReacLve Client API, Server Sent Events, …

12. Copyright © 2016, Oracle and/or its affiliates. All rights reserved. |
EvoluLon – REST
Java API – JAX-RS
12

13. Copyright © 2016, Oracle and/or its affiliates. All rights reserved. |
EvoluLon – Polling
13
Client Server
GET /hello HTTP/1.1
Header: value
…
HTTP/1.1 200 OK
Header: value
…
<enLty>

14. Copyright © 2016, Oracle and/or its affiliates. All rights reserved. |
EvoluLon – Long-Polling
14
Client Server
GET /hello HTTP/1.1
Header: value
…
HTTP/1.1 200 OK
Header: value
…
<enLty - CHUNK>
<enLty - CHUNK>

15. Copyright © 2016, Oracle and/or its affiliates. All rights reserved. |
EvoluLon – SSE
• Channel for sending events from the server to the client
• Very similar to long polling
• Accept: text/event-stream
• Semi-permanent connecLon
• Limited browser support (no IE, no Android)
• Java EE 8+ J
– Included in JAX-RS 2.1
Server Sent Events
15

16. Copyright © 2016, Oracle and/or its affiliates. All rights reserved. |
HTTP/1.1 200 OK
Content-Type: text/event-stream
Date: Tue, 06 Sep 2016 15:39:30 GMT
Transfer-Encoding: chunked
event: custom-message
data: JAX-RS 2.1
event: custom-message
data: test
event: custom-message
data: JavaOne2016
Server Sent Events
16
Client Server
GET /sse
Accept: text/event-stream

17. Copyright © 2016, Oracle and/or its affiliates. All rights reserved. |
HTTP/1.1 200 OK
Content-Type: text/event-stream
Date: Tue, 06 Sep 2016 15:39:30 GMT
Transfer-Encoding: chunked
event: custom-message
data: JAX-RS 2.1
event: custom-message
data: test
event: custom-message
data: JavaOne2016
Server Sent Events
17
Client Server
GET /sse
Accept: text/event-stream

18. Copyright © 2016, Oracle and/or its affiliates. All rights reserved. |
Server Sent Events
18
Use ExecutorService instead
P

19. Copyright © 2016, Oracle and/or its affiliates. All rights reserved. |
Server Sent Events
19 P

20. Copyright © 2016, Oracle and/or its affiliates. All rights reserved. |
Server Sent Events
20 P

21. Copyright © 2016, Oracle and/or its affiliates. All rights reserved. |
EvoluLon – WebSocket
• RFC 6455 (December 2011)
• Bi-direcLonal communicaLon
• Uses HTTP/1.1 for iniLal handshake
– Completely different protocol averwards
• “Server” and “client” endpoints are equal aver handshake
• Text or binary payload
• Supported in all modern browsers
21

22. Copyright © 2016, Oracle and/or its affiliates. All rights reserved. |
EvoluLon – WebSocket
WebSocket Frame
22

23. Copyright © 2016, Oracle and/or its affiliates. All rights reserved. |
WebSocket usecases
• RFC 7118 – SIP over WebSocket
• RFC 7355 – SIP & CLF (Common Log Format) over WebSocket
• RFC 7395 – XMPP over WebSocket
• Dravs
– MSRP (Message Session Relay Protocol) over WebSocket
– SDP (Session DescripLon Protocol) over WebSocket
– Remote Framebuffer Protocol over WebSocket
– <anything> over WebSocket
Subprotocols
23

24. Copyright © 2016, Oracle and/or its affiliates. All rights reserved. |
Java API for WebSocket
• JSR 356 – Part of Java EE 7
– 1.0 (May 2013)
– 1.1 (August 2014)
• Annotated and programmaLc way how to deploy and access WebSocket
endpoints
• Event-driven model - @OnOpen, @OnMessage, @OnError, @OnClose
• Encoders/Decoders, Path/Query parameter handling, Handshake headers
interceptors, CDI integraLon, …

25. Copyright © 2016, Oracle and/or its affiliates. All rights reserved. |
Java API for WebSocket – Annotated Endpoint

26. Copyright © 2016, Oracle and/or its affiliates. All rights reserved. |
Java API for WebSocket – ProgrammaLc Endpoint

27. Copyright © 2016, Oracle and/or its affiliates. All rights reserved. |
WebSocket vs REST
• Might seem to be similar and some people even think about WebSocket as
about another “RevoluLon” – like SOAP --> REST
• In reality, these are two different concepts which COMPLEMENT each
other.
• REST makes more sense for standard web pages, forms, …
• WebSocket provides bi-direcLonal channel, suitable for exchanging “short”
messages with the browser.
– (the scope is not limited, you can re-implement all your communicaLon with server,
but there is no point in doing that..)
27

28. Copyright © 2016, Oracle and/or its affiliates. All rights reserved. |
EvoluLon – HTTP/2
• Same semanLcs as HTTP/1.1
• Binary protocol
• MulLplexed communicaLon
– Single TCP connecLon to single origin, shared for consequent/parallel requests
• Compressed headers
– HTTP/2 introduces HPACK (compression algorithm)
• Server Push
– Server can push (cacheable) content to the client before client asks
HTTP/2 Key Features
28

29. Copyright © 2016, Oracle and/or its affiliates. All rights reserved. |
EvoluLon – HTTP/2
29
Client Server
HTTP/2 connecLon
(single TCP connecLon)
HTTP/2 streams
:method GET
:path /resource1
:method GET
:path /resourceX

30. Copyright © 2016, Oracle and/or its affiliates. All rights reserved. |
WebSocket vs HTTP/2
• Pushed resources are cached on client side
• When client decides it needs something (image, ..), it looks into the cache
– Doesn’t need to be image, but all cool demos are using that (remember SPDY)
• Server push has its own issues
– What if client does not need pushed resource? (there might be other caches, …)
– Client need to explicitly state that it accepts Server push
• Push is not an interac@ve message exchange
WebSocket vs Server push
30

31. Copyright © 2016, Oracle and/or its affiliates. All rights reserved. |
SSE and HTTP/2
31
Client Server
HTTP/2 connecLon
(single TCP connecLon)
HTTP/2 streams
:method GET
:path /sse
:method POST
:path /events
:status 200 OK
Content-type: text/event-stream

32. Copyright © 2016, Oracle and/or its affiliates. All rights reserved. |
WebSocket and HTTP/2
Standards..
32
• Currently, WebSocket is not defined in HTTP/2 world
• WebSocket uses UPGRADE header, which gives complete control over TCP
connecLon
• HTTP/2 Streams could
support WS mulLplex

33. Copyright © 2016, Oracle and/or its affiliates. All rights reserved. | 33
Usecases
HTTP SSE
WebSockets
Chat
Sta@c pages
Forms
Games
Remote control
Monitoring
Messaging / No@fica@on
X over WS
Tracking progress
Images, …
REST

34. Copyright © 2016, Oracle and/or its affiliates. All rights reserved. |
Demo
34

35. Copyright © 2016, Oracle and/or its affiliates. All rights reserved. |
Java 9
• Replace “good” old HbpURLConnecLon
• JDK 9 – JEP 110: HTTP/2 Client: hbp://openjdk.java.net/jeps/110
– Define a new HTTP client API that implements HTTP/2 and WebSocket, …
HTTP/REST & WebSocket client
35

36. Copyright © 2016, Oracle and/or its affiliates. All rights reserved. |
Next Steps
• Take the survey
– hbp://glassfish.org/survey
• Send technical comments to
– users@javaee-spec.java.net
• Join the JCP – come to Hackergarden in Java Hub
– hbps://jcp.org/en/parLcipaLon/membership_drive
• Join or track the JSRs as they progress
– hbps://java.net/projects/javaee-spec/pages/SpecificaLons
• Adopt-a-JSR
– hbps://community.oracle.com/community/java/jcp/adopt-a-jsr
Give us your feedback
36

37. Copyright © 2016, Oracle and/or its affiliates. All rights reserved. |
Where to Learn More at JavaOne
37
Session Number Session Title Day / Time
CON1558 What's New in the Java API for JSON Binding Monday 5:30 p.m
BOF7984 Java EE for the Cloud Monday 7:00 p.m
CON4022 CDI 2.0 Is Coming Tuesday 11:00 a.m
CON7983 JAX-RS 2.1 for Java EE 8 Tuesday 12:30 p.m
CON7980 Servlet 4.0: Status Update and HTTP/2 Tuesday 4:00 p.m
CON7978 Security for Java EE 8 and the Cloud Tuesday 5:30 p.m
CON7979 ConfiguraLon for Java EE 8 and the Cloud Wednesday 11:30 a.m
CON7977 Java EE Next – HTTP/2 and REST Wednesday 1:00 p.m
CON6077 The Illusion of Statelessness Wednesday 4:30 p.m
CON 7981 JSF 2.3 Thursday 11:30 a.m

38. Copyright © 2016, Oracle and/or its affiliates. All rights reserved. |
Contacts/QA
• Pavel Bucek (pavel.bucek@oracle.com)
• Jersey / JAX-RS RI : hbp://jersey.java.net
– users@jersey.java.net
• Tyrus / WebSocket RI : hbp://tyrus.java.net
– users@tyrus.java.net
Feel free to ask any quesLons now or contact me later.
38

41. Copyright © 2016, Oracle and/or its affiliates. All rights reserved. |
WebSocket and Clustering
• Different to “classic” cluster
– We’d like to talk to other sessions (clients) directly
• Clustered environment present different challenges
– “Finding a WebSocket Session” might not be as trivial as it seem
• Broadcast (mass-noLficaLon) is common usecase
• Clustering can help
– BroadcasLng to “all sessions” can be faster in clustered environment
41

42. Copyright © 2016, Oracle and/or its affiliates. All rights reserved. |
WebSocket and Clustering
42
JMS,
JCache,
Coherence,
…
Load Balancer

43. Copyright © 2016, Oracle and/or its affiliates. All rights reserved. |
WebSocket and Clustering
43
JMS,
JCache,
Coherence,
…
Load Balancer

44. Copyright © 2016, Oracle and/or its affiliates. All rights reserved. |
WebSocket and Clustering
44
JMS,
JCache,
Coherence,
…
Load Balancer

45. Copyright © 2016, Oracle and/or its affiliates. All rights reserved. |
WebSocket and Clustering
45
JMS,
JCache,
Coherence,
…
Load Balancer

46. Copyright © 2016, Oracle and/or its affiliates. All rights reserved. |
WebSocket and Clustering
• Different requirements
• Load balancers might need to manage more open connecLons
• Cannot re-balance when session is already created
– Node is added – ok, but I cannot easily decrease load on other nodes, I can use the
new node only for new connecLons
• Node going down is not transparent to client
– Robust clients can hide this, but for now, this requires custom soluLon
– WLS 12.2.1 offers a soluLon for this..
46

47. Copyright © 2016, Oracle and/or its affiliates. All rights reserved. |
WebSocket and Clustering
47
JMS,
JCache,
Coherence,
…
Load Balancer

48. Copyright © 2016, Oracle and/or its affiliates. All rights reserved. |
WebSocket and Clustering
48
JMS,
JCache,
Coherence,
…
Load Balancer

49. Copyright © 2016, Oracle and/or its affiliates. All rights reserved. |
WebSocket and Clustering
• Might require more applicaLon code
– Proper handling on client side
– Even more code when you want to have something like auto reconnect + “session
recovery”
• Infrastructure requirements
– Similar to SSL (persistent connecLon, …)
• Much more effecLve when compared to the same app implemented using
long-polling
49