OSGi Community Event 2016 Presentation by Nedelcho Delchev (SAP) How to use WebSockets, coming as a standard feature with the modern Servlet Containers (e.g. Tomcat 7.x) from within the embedded Equinox OSGi environment deployed as a WAR application archive? This talk will explain in details how to configure the classloaders and dependencies as well as how to create a websocket bridge for the internal OSGi plugins.

1. WebSockets and Equinox OSGi in
a Servlet Container
Nedelcho Delchev [SAP]
2016-10-27

2. Who am I?
I am Development Architect in HANA
Cloud Platform Core team in the area
of extensions for large enterprises in
the cloud.
Project lead of Eclipse Dirigible – a Cloud
Development Platform project that provides full-
fledged capabilities for developing, running and
operating cloud applications –
http://www.dirigible.io

3. ServletBridge Architecture
• Server-Side Equinox:
http://www.eclipse.org/equinox/server/
• Equinox in a Servlet Container:
http://www.eclipse.org/equinox/server/http_in_
container.php
• What is OSGi in Servlet Container series by
Angelo Zerr:
https://angelozerr.wordpress.com/2010/08/31/o
sgi-equinox-in-a-servlet-container-step0/

4. ServletBridge Component
Web Container
Servlet Bridge
OSGi
Servlet
OSGi
Servlet
Servlet

5. Websockets
https://www.pubnub.com/blog/2014-10-01-websockets-and-long-polling-in-
javascript-ruby-and-python/
https://www.tutorialspoint.com/websockets/websockets_quick_guide.htm

6. WebSocket Bridge in WebApp

7. WebSocket Servlet in OSGi

8. Registering OSGi WS Servlet in the
BundleActivator

9. Websocket in Web Container
Web Container
ServletBridge [Registered
OSGi WS Servlets]
OSGi WS
Servlet
Websocket Servlet
1
2
3
1. Registering 2. Lookup 3. Communication

10. Classloaders visibility (launch.ini)
osgi.*=@null
org.osgi.*=@null
eclipse.*=@null
osgi.parentClassloader=fwk
osgi.contextClassLoaderParent=fwk
org.osgi.framework.system.packages.extra=javax.w
ebsocket,javax.websocket.server,javax.mail,javax.m
ail.internet,osgi.websockets.bridge

11. Authentication and Authorization
• Logged-in User
• Is User in Role?

12. “Hello World” via Websocket channel
• Clone –
https://github.com/delchev/WebSockets_EquinoxOSGi_ServletCont
ainer.git
• Build & Deploy
• Access & Login - http://localhost:8080/services/standard
• Create WS Client e.g. in Chrome –
> var logSocket = new WebSocket("ws://localhost:8080/log");
• Inspect Frames in Network/WS
• Access from a second browser -
http://localhost:8080/services/standard
• Send a message from WS client and receive the echo -
logSocket.send("Hello from Client!");

13. Real-world examples
• By Eclipse Dirigible

14. Log Console

15. Terminal

16. Debug

17. Scripting Services
http://www.dirigible.io/api/websocket.html

18. Recap
• You learnt that you can utilize WebSockets in a
OSGi environment
• You learnt how to do it via the ‘bridge’ concept
• You learnt that it is not just pure theoretical
thing, but it is already used in the real world
projects
• You got it re-confirmed OSGi is cool
• You learnt about existence of an OSGi based
Cloud Development Platform project called
Eclipse Dirigible: http://www.dirigible.io

19. Thank You!

20. References
• http://www.dirigible.io/blogs/2016/05/19/blo
gs_web_sockets_and_osgi_in_servlet_contain
er.html