1. Introduction to JRuby
Design by Mr.Huân

2. What is JRuby?
 JRuby is an implementation of Ruby programming
language that runs on the Java Virtual Machine(JVM).
 Started in 2002, open source, many contributors.
 Releases
> June 2007: 1.0 release, focus on compatibility.
> April 2008: 1.1 release, focus on performance.
 Aiming for compatibility with current Ruby version.
> JRuby 1.7.6 is compatible with: Ruby 1.9.3

3. Why Use JRuby?
•
With JRuby you get the best of both worlds: Ruby
applications and libraries,plus Java libraries. And you can
access those libraries with Ruby syntax (or Java syntax, if
you want).
•
On average JRuby, runs 2 and a half times faster than
Ruby, except at startup.
•
In addition to native threads, JRuby supports Unicode
Natively.
•
Code can be fully compiled ahead of time or just in time.

4. Install JRuby and JRuby Gems
• Download and install JRuby
-
Download: http://jruby.org/download
-
Instructions:
https://github.com/jruby/jruby/wiki/GettingStarted
-
In linux : rvm install jruby or rbenv install jruby
• Install JRuby Gems:
-
jruby -S gem install rails mongrel

5. Calling Java From JRuby
include Java & import:
include Java statement will give you access to the bundled Java
libraries. However, this will not give you access to non-bundled
libraries.

• The import statement is used to import a Java Class.
include Java
import java.util.ArrayList
import javax.swing.JFrame
list = ArrayList.new
frame = javax.swing.JFrame.new("Passion!")
list << frame
list.each {|f| f.set_size(200,200) }

6. Calling Java From JRuby (cont)
include_package within a JRuby Module:
•
Use include_package"<package_name>"in a JRuby
Module to support namespaced access to the Java classes
in the package.
include Java
module JavaLang
include_package "java.lang"
end
s = JavaLang::String.new("This is my string from java.lang
package")

7. Calling Java From JRuby (cont)
include_class:
•
Use include_class "<class_name>" to include unbundled
Java classes.
• The unbundled Java classes(in the form of jar file) should
be in the classpath.
include Java
include_class 'mypackage.Hello'
h = Hello.new
puts "----Invoke a method of from Hello object"
s = h.sayHello("Message from Hello Java Class!")

8. JRuby on Rails
You can use JRuby with Ruby on Rails. JRuby gives Rails
the power and functionality of the Java Platform, providing it
with:
• Excellent garbage collection for endless uptimes.
• Hotspot profiled dynamic optimizations for great
performance.
• Access to the Java ecosphere for additional technology
options.
• Deployment to Java application servers for ubiquity.

9. JRuby on Rails
• Create a new JRuby on Rails app:
-
gem install rails
-
rails new blog
-
rails new my_app -m http://jruby.org/rails3.rb
• /Gemfile
-
gem 'activerecord-jdbcsqlite3-adapter‘
-
gem 'jruby-openssl'
-
gem 'therubyrhino'

10. Deployment
• Use JRuby, you can use a Java application servers:
Tomcat , Glassfish, Jetty, Jboss…
•
To deploy to a Java app server, you can use the tool
Warbler to bundle your Rails application in a Java Web
Application Archive.
•
Once you have a .war file, you can deploy to any Java
app server using its war deployment mechanism

11. Demo

12. Thank for watching