Delivered at JavaOne (2008). Discusses differences between Java & Ruby and how you can use the two together.

1. From Java To Ruby … and Back
Anil Hemrajani, Founder, BigUniverse.com
TS-4868, anil@biguniverse.com

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Agenda
My Background & BigUniverse.com
Core Ruby Technologies
Ruby on Rails
Java™ platform & Ruby Compared
Using the Java platform & Ruby Together
Tools
Wrap Up & Resources

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My Background
20+ years of software development
• Custom apps & products - AT&T, IBM, AOL, Fannie Mae, startups. . .
• Programming Languages
• Since 2006 - Working exclusively with Ruby/Rails
• 1995 to 2006 - 11+ with the Java platform
• Before that - C , C++, Unix®
Shell software, PERL, etc.
• OS, Database, Tools, etc. - Unix, Linux, Windows, Mac OS X, MySQL™,
Oracle®
, Sybase, Informix, Eclipse, NetBeans™, Visual Café, JBuilder
software and many more!
Author & speaker
• Published top-rated book on Java™ platform (available in 4 languages)
• Published dozens articles
• Presented in 4 continents to thousands of attendees
Other: Won several industry awards, founder of two companies…
details on visualpatterns.com.
At present: BigUniverse.com

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About BigUniverse.com
A World of Online Children’s Picture Books
Built using:
• Ubuntu Linux (using Xen Virtualization)
• Apache Mongrel Cluster (may move to Java Server soon)
• Ruby Rails
• MySQL
• OpenLaszlo
• DHTML/AJAX
• Development on combination of Mac OS X and Windows
Tools Used: Eclipse, Aqua Studio CocoaMySQL, Ruby irb Rails
script/console, capistrano deprec, and more
“Read, create, publish buy
children’s picture books”

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Big Universe Website Products
Website
Books, tools, blogs, global awareness…
Big Universe Author™
Book creation publishing tool with 7,000
vector graphic cliparts
Big Universe Reader™
300+ (and growing) high-quality fiction non-
fiction books readable online

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Why We Chose Ruby?
Primarily because of the Rails framework
I resisted the hype of Rails for 1+ year but finally:
• Took the advise of many intelligent pragmatic developers I know
• Spent 4+ weeks developing with it
• Conclusion? The hype is mostly true; productivity is very high
Business Technical benefits seen so far
Rapid prototyping/development because:
• Language is concise and easy to read
• Single-stack application framework (web MVC, ORM, unit testing…)
• Almost no configuration required (No XML hell!)
• Dynamically typed
• Can be used for full OO applications or just procedural scripting
• No compilation (prediction: in 5+ years, we will do away with compilation
for 80% of the application development; just like we did away with linking)
• More…

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Agenda
My Background BigUniverse.com
Core Ruby Technologies
Ruby on Rails
Java platform Ruby Compared
Using Java platform Ruby Together
Tools
Wrap Up Resources

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How many of you
have already
worked with Ruby
and/or Rails?
Quick Poll

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RubyGems
gem Rails (gem)
RUBY INTERPRETER
gem gem
The Basics
Ruby Interpreter
Ruby Libraries and/or Gems

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What is Ruby?
History
• Created by Yukihiro Matz Matsumoto
• Started working on Ruby on February 24, 1993
• Released it to the public in 1995
• Named so because of a joke, alluding to PERL's name
Can Be Used For
• Full-blown OO Applications (e.g. web applications, web services,
messaging, GUI, and much more!)
• Procedural scripting
Version
• 1.8.6 - latest stable (March 2008)
• 1.9 - with some major changes (coming soon)
Site: http://ruby-lang.org/

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Notice
Dynamic
Types
Ruby Syntax Examples
Everything is an object
5.times {|i| puts Hello #{i} }
Array
a = [1, 'hi', 3.14, 1, 2]
a.reverse
a.each { |x| puts x }
Hash
h = {:water = 'wet', :fire = 'hot'}
h.each_pair do |key, value|
puts #{key} is #{value}
end
Ranges
(0..2).each {|i| puts i} #= [0, 1, 2]
('a'...'e').to_a #= [a, b, c, d]

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Ruby Syntax Examples (cont’d)
Classes Methods
class Person
attr_accessor :name,
:age
def initialize(name,
age)
@name, @age = name,
age
end
end
...
p = Person.new(jay, 29)
p.name
jay”
Exceptions
raise ArgumentError,
Illegal arguments!”
...
begin
# Do something
rescue
# Handle exception
end

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Ruby Syntax Examples (cont’d)
Returning multiple parameters
class MyClass
def mymethod
return 1, 2
end
end
a = MyClass.new
b, c = a.mymethod
Reflection
a = MyClass.new
a.public_methods
a.respond_to? mymethod
I/O
File.readlines('README').each do |line|
puts line
end

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What is RubyGems?
Standard format for distributing Ruby programs/libraries
• Available gem server utility for serving gems from any machine
• Default gem server: rubyforge.org (as of March, 2008: 5,400+ projects)
• Install can automatically fetch dependencies
Sample commands
gem install rails
gem list --local
Sample gems we use:
• rails (yes, Rails is a gem)
• ferret (for searching)
• crypt (encrypted decrypting using a variety of ciphers)
• redcloth (text markup)
• glassfish_rails (discussed later in this presentation)
• Others: capistrano, deprec, rake, termios, etc.
Version - 1.0.1 (December, 2007)
Site: http://rubygems.org/

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Agenda
My Background BigUniverse.com
Core Ruby Technologies
Ruby on Rails
Java platform Ruby Compared
Using Java platform Ruby Together
Tools
Wrap Up Resources

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What is Ruby on Rails?
Short names: Rails (or RoR)
A full-stack, web application, development framework:
• Web MVC framework
• Complex OR Mapping
• Unit testing
• Rake utility (similar to Ant, make, etc.)
• Database migrations
• AJAX/UI support (via prototype library)
• Web layouts (similar to DisplayTag, ValueList, etc.)
• Built-in web server
• Code generation (controllers, models, migration…)
• Support for 3rd-party plug-ins
• More…
Version: 2.0.x (Dec, 2007)
Site: http://rubyonrails.org/

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Rails Basics
MVC Web Application Framework
• Action Pack: Controllers Views
• Active Record: Model
ActiveMailer (send emails)
Some built-in utilities
• script/server (Bundled web server)
• script/console (of Ruby’s “irb”)
• script/generate (generate code for controllers, model, views,
migrations, scaffold…)
• script/plugin (install 3rd-party plugins; e.g. incorporate in model
classes acts_as_ferret :fields = [ 'title', 'body' ])
• rake db:migrate (run migrations)

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Sample Rails DB App in Minutes
One-time system-wide install of Rails framework
gem install rails
Generate application
rails -d mysql buapp
Edit config/database.yml (the only required config!)
development:
adapter: mysql
database: buapp_development
username: root
password:
Create database
rake db:create
Quick test via “scaffolding”
ruby script/generate scaffold Developer name:string

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Sample Rails DB App in Minutes (cont’d)
Run migration script: rake db:migrate
Start bundled web server: ruby script/server
Access: http://localhost:3000/developers/

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Sample Custom Rails Code
Model (app/models/developer.rb)
class Developer ActiveRecord::Base
has_many :tasks
belongs_to :team
validates_presence_of :name
end
Controller (app/controllers/show_controller.rb)
class ShowController ApplicationController
def index
@developers = Developer.find(:all, :order = name)
end
end
View (app/views/show/index.html.erb)
ol
% for developer in @developers %
li%= developer.name %/li
% end %
/ol

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Typical Rails Development Activities
Generate/write models, controllers, and views:
• Models (e.g. one or many-to-many relationships, field validations,
methods)
• Custom “layouts” and CSS (for site/section wide consistent look-and-feel)
• Custom database code in controllers
• Custom “helpers” (code to use in views)
• Before/after controller “filters”
Add libraries/gems/plug-ins (e.g. ferret, crypt)
Configuration: environments/*.rb, routes.rb, etc.
Other: ActionMailer, stylesheets, javascripts, html/images…

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Agenda
My Background BigUniverse.com
Core Ruby Technologies
Ruby on Rails
Java platform Ruby Compared
Using Java platform Ruby Together
Tools
Wrap Up Resources

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Comparing Java Platform Ruby
Syntax
Conventions
Benchmarks

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Syntax
import java.sql.*;
public class LoadFileIntoDB {
public int doLoad(String fileName)
throws Exception {
BufferedReader br =
new BufferedReader(new FileReader(fileName));
...
}
require 'mysql'
class LoadFileIntoDB
def do_load(file_name)
f = File.open file_name
...
end

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myclass.rbMyClass.javaFile name
MyClassMyClassClass
my_methodmyMethodMethod
my_variablemyVariableVariables
MIN_LENGTHMIN_LENGTHConstant
=begin
some code
=end
/* */ or /** */Block Comments
#//Single-line Comments
RubyJava
Code Conventions

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223.64230.843Database (insert/fetch 10 thousand rows)
1.4694.641Socket (download 1MB file)
17.4375.75File I/O (write/read 1 million lines)
13.7660.125Loops (100 million times)
0.0160.046Threads (spawn 100)
Ruby
(sec)
Java
(sec)
Function
Code/Details available at: http://visualpatterns.com/javaruby.php
(Amateur) Benchmarks

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Agenda
My Background BigUniverse.com
Core Ruby Technologies
Ruby on Rails
Java platform Ruby Compared
Using Java platform Ruby Together
Tools
Wrap Up Resources

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How many of you
are already
working with
JRuby?
Quick Poll

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Why Java Ruby/Rails Together?
The Java platform is a robust and time-tested technology
Rails is an elegant MVC framework for DB-web apps
JRuby brings the maturity of the Java platform to the world of
Ruby/Rails
Rails applications can be deployed in Java servers -- benefits include:
• a single container versus multiple instances of Mongrel
• out-of-box clustering and pooling features of many Java servers
• Organizations can maximize their existing investments in Java servers
• take advantage of Java platform features (e.g. Servlet Filters) or access Java
JARs/libraries (e.g. Google’s OpenSocial Shindig)

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What is JRuby?
A 1.8.6 compatible Ruby interpreter written in 100% pure
Java platform
Most built-in Ruby classes provided
Support for interacting with and defining Java server
classes from within Ruby
Bean Scripting Framework (BSF) support
Distributed under a tri-license (CPL/GPL/LGPL)
A very active project:
• 1.1RC2 - Feb, 2008
• 1.0.3 - December, 2007
• 1.0 - June, 2007
• 0.9.9 - April, 2007
• 0.9.8 - March, 2007

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Ways Java Platform Ruby Can Work
Together
Deploy Rails application In Java servers
• GoldSpike (WAR file)
• GoldSpike Rails Plugin
• Warbler (http://caldersphere.rubyforge.org/warbler/)
• The Grizzly Project (run Rails apps directly)
• Using the Grizzly project as a standalone (https://grizzly.dev.java.net)
• Inside GlassFish™ Project (https://glassfish.dev.java.net/)
Call Ruby from Java platform
• JRuby API
• Ruby ruby = Ruby.getDefaultInstance();
• IRubyObject result = ruby.evalScriptlet(1 + 1);
• Bean Scripting Framework (BSF)
• JSR-223: Scripting for the Java™ Platform
• Runtime.exec
Call Java server class from Ruby scripts using JRuby

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Calling Java Server Classes in Ruby
jruby swingdemo.rb
require 'java'
parent = javax.swing.JFrame.new(Window)
chooser = javax.swing.JFileChooser.new()
return_val = chooser.showOpenDialog(parent)
if return_val == 0
puts chooser.getSelectedFile().getName()
end
parent.dispose

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Calling Ruby from Java Platform
Using JRuby API
import org.jruby.*;
public class CallRuby
{
public static void main(String args[])
throws Exception
{
Ruby ruby = Ruby.getDefaultInstance();
String rubyScript = puts Ruby interpreted at
#{Time.now};
ruby.evalScript(rubyScript);
}
}

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Call Ruby from Java Platform (cont’d)
Using Runtime.exec
public class RunRuby
{
public static void main(String args[])
throws Exception
{
Process p = Runtime.getRuntime().exec(ruby
+ args[0]);
BufferedReader br = new BufferedReader(new
InputStreamReader(p.getInputStream()));
String line;
while ((line = br.readLine()) != null)
System.out.println(line);
p.waitFor();
System.out.println(rc = + p.exitValue());
}
}

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Deploy Style #1: WAR File
Install JRuby and set JRUBY_HOME
Install gems under JRuby gems directory
jruby -S gem install rails activerecord-jdbc-
adapter -y --no-ri --no-rdoc
Generate Rails app (done earlier in our presentation)
Use JDBC™ technology in config/database.yml
development:
adapter: jdbc
driver: com.mysql.jdbc.Driver
url: jdbc:mysql://localhost/buapp_development
username: root
password:

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Deploy Style #1: WAR File (cont’d)
Install GoldSpike plugin for app
jruby script/plugin install
svn://rubyforge.org/var/svn/jruby-extras/trunk/rails-
integration/plugins/goldspike
Creating, testing deploying WAR file
• jruby script/generate goldspike
• Copy required JAR files to WEB-INF/lib (e.g. mysql*.jar)
• Test app:
• jruby -S rake war:standalone:run
• http://localhost:8080/buapp/developers/
• Create WAR:
jruby -S rake war:standalone:create
• Deploy buapp.war to web server
(e.g. Tomcat’s webapps directory)
NOTE:
warbler is a
preferred
method but did
not support
Rails 2.0 at
time this
presentation
was developed

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Install GlassFish v3, Technology Preview 1:
java -jar glassfish*.jar
Run server: java -jar lib/glassfish*SNAPSHOT.jar
(from glassfish directory)
Deploy sample app:
glassfish/bin/asadmin deploy --path hello
Access it:
http://localhost:8080/hello/
Deploy Style #2: Directly With GlassFish v3
Source: http://blogs.sun.com/arungupta/entry/
first_jruby_on_rails_app

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Deploy Style #3: glassfish_rails gem (cool!)
Install it: jruby -S gem install glassfish
Run it:
glassfish_rails hello
INFO: Listening on port 8080
Oct 8, 2007 11:13:01 PM
com.sun.enterprise.v3.services.impl.DeploymentService
postConstruct
INFO: Supported containers : web,phobos,jruby,php
Oct 8, 2007 11:13:01 PM
com.sun.enterprise.v3.server.AppServerStartup run
INFO: Glassfish v3 started in 1316 ms
Access it:
http://localhost:8080/

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mod_proxy
Apache HTTP
Server (80)
Internet
DB
Mongrel/Rails
Server (8001)
Mongrel/Rails
Server (8002)
Mongrel/Rails
Server (8003)
Mongrel/Rails
Server (8004)
Mongrel Cluster
Internet
Tomcat or
other Java
App Server
DB
Apache HTTP
Server (80)
Java Server
Sample Configurations

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Agenda
My Background BigUniverse.com
Core Ruby Technologies
Ruby on Rails
Java Ruby Compared
Using Java Ruby Together
Tools
Wrap Up Resources

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Tools
IDEs Editors
Capistrano (automate application deployment)
Handy command-line utilities

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NetBeans Ruby Pack Software
code highlighting
completion,
debugger,
refactoring…

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Eclipse With RDT or Aptana/RadRails

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Capistrano: Automate App Deployment
apache_install
apache_restart
change_root_password
deploy
deploy_with_migrations
disable_web
enable_web
execute_mysql
install_apache
install_gems
install_php
install_postfix
install_rails_stack
install_rmagick
install_rubygems
restart_apache
restart_app
restart_mongrel_cluster
setup_admin_account_as_root
setup_mysql
setup_scm
setup_smtp_server
setup_ssh_keys
start_apache
start_app
start_mongrel_cluster
stop_apache
stop_mongrel_cluster
trac_install
Many others…
Partial List of Tasks (can also write custom tasks)

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Handy Command-Line Utilities
$ irb
irb(main):001:0 Time.now
= Sun Sep 30 19:47:55 -0400 2007
irb(main):002:0
$ script/console
Loading development environment.
Blog.find(:all)
$ ri String
----------------------------------------------------
A +String+ object holds and manipulates ...
Includes:
---------
Comparable(, =, ==, , =, between?)
Enumerable(all?, any?, collect, detect, each_cons,
each_slice, each_with_index, entries,

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Agenda
My Background BigUniverse.com
Core Ruby Technologies
Ruby on Rails
Java Ruby Compared
Using Java Ruby Together
Tools
Wrap Up Resources

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Learning Ruby Rails
• Master Ruby before Rails (IMHO)
• Try small Ruby scripts, then classes, then more complex stuff (e.g.
mixins, modules), and so on…
• After spending a couple of days with Ruby, move on to Rails
For Rails
• Start with sample app and scaffold, then iteratively develop from
there (build app in increments)
• If something seems tough in Rails, you are probably doing it wrong
Other
• Use “irb” and “console” whenever possible
• Use capistrano for remote deployment
Recommendations

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Online Resources
Official sites
• ruby-lang.org
• rubyonrails.org
• jruby.org
• netbeans.org
• glassfish.dev.java.net
Documentation
• ruby-doc.org
• railsbrain.com
Forums
• ruby-forum.com
• railsforum.com
Screencasts
• railscasts.com
• peepcode.com
Blogs
• headius.blogspot.com
• blogs.sun.com/arungupta/
Sample Real World Rails/JRuby sites
• mediacast.sun.com
• mix.oracle.com
Other
• 10 things every Java programmer
should know about Ruby -
onestepback.org/articles/10things/

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Agenda
My Background BigUniverse.com
Core Ruby Technologies
Ruby on Rails
Java platform Ruby Compared
Using Java platform Ruby Together
Tools
Wrap Up Resources

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Visit BigUniverse.com
to see a live demo of our site!
…and don’t hesitate to contact me:
anil@biguniverse.com
Thank You For Attending!