JRuby allows Ruby code to run on the Java Virtual Machine. It provides the ability to reuse existing Java libraries and deploy Ruby applications in scalable and enterprise-ready environments. While Java may have a reputation for being slow, JRuby performance is on par with CRuby for most web applications due to JIT compilation optimizations in the JVM. Calling between Ruby and Java code is seamless, allowing Ruby code to leverage Java libraries and Java code to leverage Ruby code. JRuby applications can be packaged and deployed like standard Java applications.

1. Ram Vijapurapu
@rvijapurapu

2. What is JRuby?
Its just Ruby
Running on the JVM
(Java Virtual Machine)

3. Conclusion
..I truly wish it is that simple.
Image credit: http://www.flickr.com/photos/hordurk/3204191929/

4. Social Context

5. Social Context

6. Social Context

7. Why do we want to go back to the
Haunted House again?
● Reuse what's already built
Enterprise Ready
● Need of a Scalable Platform
^
● Need for an inclusive Platform
– Ruby, Groovy, Python, JS, ..
●
Generally Love of Engineering
Genius

8. What is the first thing you hear
about Java?
Image credit: http://bit.ly/btxcPf

9. Common Man! Java is Slooow
● Maybe... Maybe not!
ACHTUNG! Highly Unscientific Testing

10. Common Man! Java is Slooow
No
Optimizations

11. Common Man! Java is Slooow
100

12. Common Man! Java is Slooow
1,000

13. Common Man! Java is Slooow
10,000

14. Common Man! Java is Slooow
100,000

15. Common Man! Java is Slooow
100,000
What's your Point?
See Java is sl0000w!

16. st
a
Common Man! Java is Slooow
F
1,000,000

17. st
F a
Common Man! Java is Slooow
Fast
1,000,000
Clearly you
fudged it!

18. You fudged it!
● Maybe – but there is method in madness

19. You fudged it!
Moral: Focus on your code
● Maybe JVM there is care ofin madness
& – but takes method the rest
– well into the future
Performance Improvements in JVM from
1.5 to 1.6 have been significant. both are
running i386

20. What just happened?
● Magic – JVM/Hotspot (Dark Magic?)
● JIT (Just In Time Compilation) – Optimization on the
Fly
● Speaking further on this is beyond the scope of this
presentation _
Summary: Normal usage on Web you will find
JRuby performs same as CRuby

21. As all good things in life........
there are few limitations
● You cannot use libraries which use CRuby
Extensions
● Java Threads
● Posix Methods
● Does not support continuations/bindings.
(Feature Missing)
http://docs.codehaus.org/display/JRUBY/Limitations

22. Same stuff – Different Different
● ruby ● jruby
● Irb ● jirb
● rake ● jruby -S rake
● gem ● jruby -S gem
Include jruby-complete.jar or jruby.jar in
your CLASSPATH & PATH for the
executable

23. Show me stuff... JRuby
integration with JVM
Ruby'ized – by popular demand!

24. Choose your Hammer – Calling
Ruby from within Java

25. Choose your Hammer – Calling
Ruby from within Java
JSR 223

26. Choose your Hammer – Calling
Ruby & Groovy from within Java

27. Choose your Hammer – Calling
Ruby & Groovy from within Java
Why would we want to do
this? Because we can

28. Choose your Hammer – Calling
JRuby file from within Java

29. Choose your Hammer – Calling
JRuby file from within Java

30. Ruby > Java

31. Ruby > Java & Back
[SNIPPED]

32. Ruby > Java & Back

33. Performance & External Libraries
● For the sake of performance it would be better
to use Java Libraries over JRuby at times.
● Totally depends on your requirement.
● Including external Java libraries within your
JRuby Code is fairly straightforward
● You can also put the jar files in the rails lib directory
for getting access to them in your rails application

34. JfreeChart – Chart Generation
● All you need to do is either have the jars in your
classpath
● Or include it in your libs folder in rails.
http://kfahlgren.com/blog/2007/04/13/jruby-jfreechart-sparklines/

35. JRuby & Library Jars

36. This guy is boring why doesn't he
just show me rails

37. The Holy Blog

38. ...

39. ...

40. DB Stuff

41. Packaging...

42. Packaging & Deploying
config/warble.rb

43. Voila

44. In Summary
● I strongly believe JVM should be your platform
Strategy
● This more or less comes out of my experience.
● JRuby will fit into many cloud architectures with little
effort (Not sure of Azure yet)
– Portability from within

45. Useful Links
● http://jruby.org/
● http://www.infoq.com/vendorcontent/show.action?vc
● http://code.google.com/p/appengine-jruby/ >
http://rails-depot.appspot.com/
● http://en.wikipedia.org/wiki/JRuby#Performance

46. Ram Vijapurapu
@rvijapurapu
thinkbelievedo.com