Why would a Java shop want to use Ruby?

Why would a Java Shop
want to use Ruby?
Keith Pitty
Open Source Developers’ Conference
Brisbane
29 November 2007

About Keith
• Programming professionally since 1983
• Early experience on mainframes
• Smalltalk was my ﬁrst OO language
• Employed by a Java consultancy since 2000
• Fascinated by Ruby and Rails since 2004
• Enjoy sampling a wide range of beers

Why would a Java Shop want to use Ruby? Keith Pitty OSDC, 29 November 2007

Java


Ruby


Java
public class print {
public static void main(String[] args) {
System.out.println(quot;Hi, I'm Javaquot;);
}
}


Ruby

#!/usr/bin/env ruby

puts quot;Hi, I'm Rubyquot;


No!!!
• This is not a language war!
• Java and Ruby both have their
strengths
• I’m not interested in Ruby
“beating” Java
• The question is:
• Can Ruby help Java programmers?


Java
• Most popular language (21.7%)
• TIOBE PCI, September 2007
• Mature platform
• Trusted in the “enterprise”
• Has reached a plateau
• “The new COBOL”


Ruby
• Tenth most popular language (2.1%)
• Marked increase in popularity since
mid-2006 due to Ruby on Rails
• Matz’s original motivation:
• a scripting language
• more powerful than Perl
• more object-oriented than Python


Why Ruby?
(Quote Part 1)
“I don’t believe there would be any real technical
beneﬁt. There may be a productivity boost, but when
you consider how much time is used by developers, QA,
etc... to bring in a new technology, chances are the net
[beneﬁt] won’t be that great.”


Why Ruby?
(Quote Part 2)
“I think the best argument for Ruby is that
your developers want it. If the developers are
yearning for new technology, it’s probably
worth considering. Happy developers code
more and code better.”

Norman Richards, JBoss


Perspectives
• Vendors
• Open source contributors
• Managers
• Business owners
• Developers


Ruby: Why not?
• How widespread is knowledge of
Ruby within the Java community?
• In my experience, there is
limited awareness
• On the other hand:
• Ruby may have beneﬁts that are
complementary to Java


Potential Ruby
Beneﬁts
• Ruby skills may complement Java skills
• Learning Ruby may be interesting,
broadening a programmer’s thinking
• Happier programmers
• Quicker time to market


Enough Preamble

• What does Ruby have to offer
people in Java development shops?
• Let’s explore some speciﬁcs...


Ruby Scripts


Ruby Scripts
• Scripts help with repetitive tasks
• Shell scripts, SQL scripts, Ant scripts
• Sometimes the logic lends itself to a general
purpose language
• Can run a Java application via a shell script
• A Ruby script is interpreted directly and is
more concise


Ruby Script Example

• Deleting ﬁles within a given
directory according to given
criteria
• e.g. older than a given time


Ruby Script Example*
#!/usr/bin/env ruby
def delete_if(dir)
Dir.chdir(dir) do
Dir.foreach(*.*) do |entry|
next if File.stat(entry).directory?
if yield entry
File.unlink(entry)
end
end
end
end

delete_if(quot;/tmpquot;) { |f| File.mtime(f) <
Time.local(2007,10,29,0,0,0) }

* See Hal Fulton’s “The Ruby Way”

Rake and Internal DSLs


Rake
• Ruby-based build language
• Developed by Jim Weirach
• Similar to make and ant

• An internal Domain Speciﬁc Language
• make and ant are external DSLs


Regular Rake Tasks
task :init do
# init actions
end

task :compile => [:init] do
# compile actions
end

task :build =>
[:init, :compile] do
# build actions
end


Extending Rake*
def copyTask srcGlob, targetDirSuffix, taskSymbol
targetDir = File.join BUILD_DIR, targetDirSuffix
mkdir_p targetDir, QUIET
FileList[srcGlob].each do |f|
target = File.join targetDir, File.basename(f)
file target => [f] do |t|
cp f, target
end
task taskSymbol => target
end
end

copyTask 'articles/*.gif', 'articles', :articles

* see Martin Fowler’s rake article

Internal DSLs
• Other Ruby internal
DSLs:
• buildr
• capistrano
• ...
• create your own!


Buildr
• a build system for Java apps
• encompasses Maven and Ant
• written in Ruby
• based on Rake
• uses Antwrap to conﬁgure and run Ant tasks
• extensible in Ruby


Capistrano
• Created by Jamis Buck
• Originally to “ease the pain of
deploying Rails applications”
• Exposes simple commands
• Once project has been “capiﬁed”
• $ cap deploy

• Useful beyond Rails


Capistrano Example
desc quot;Copy production database config file.quot;
namespace :deploy do
task :after_update_code, :roles => :app do
db_config = quot;#{shared_path}/config/database.yml.productionquot;
run quot;cp #{db_config} #{release_path}/config/database.ymlquot;
end
end


Metaprogramming


Metaprogramming
• Very powerful feature of Ruby
• Dynamic programming
• Methods: method_missing, define_method,
module_eval, class_eval, instance_eval,
self.included, self.inherited, extend

• Callable objects: procs, lambdas, blocks
• Modifying the singleton class: class <<


method_missing
class Roman
def roman_to_int(str)
# ...
end

def method_missing(methId)
str = methId.id2name
roman_to_int(str)
end
end

r = Roman.new
r.iv #=> 4
r.xxiii #=> 23
r.mm #=> 2000


More Examples?

• Open source Ruby frameworks
• e.g. Ruby on Rails web application
framework
• many examples of
metaprogramming to be found
in the Rails source code


Ruby on Rails


Ruby on Rails
• Web application framework released by
David Heinemeier Hansson in 2004
• Extracted from the Basecamp application
• The killer app for Ruby
• “Convention over Conﬁguration”
• Code generators


Rails Example
$ rails beers

Creates directory
structure for new
project


Generating a
Resource
$ ./script/generate scaffold_resource beer name:string

Creates a model, a controller, and a set of
templates that's ready to use as the
starting point for your REST-like,
resource-oriented application.


Migration
class CreateBeers < ActiveRecord::Migration
def self.up
create_table :beers do |t|
t.column :name, :string
end
end

def self.down
drop_table :beers
end
end


Running Migrations
$ rake db:migrate

== CreateBeers: migrating
=====================================================
-- create_table(:beers)
-> 0.0735s
== CreateBeers: migrated (0.0737s)
============================================


Model

class Beer < ActiveRecord::Base
has_many :votes
end


View (new.rhtml)
<h1>New beer</h1>

<%= error_messages_for :beer %>

<% form_for(:beer, :url => beers_path) do |f| %>
<p>
<b>Name</b><br />
<%= f.text_field :name %>
</p>

<p>
<%= submit_tag quot;Createquot; %>
</p>
<% end %>

<%= link_to 'Back', beers_path %>


Controller
class BeersController < ApplicationController

def new
@beer = Beer.new
end

def create
@beer = Beer.new(params[:beer])
respond_to do |format|
if @beer.save
flash[:notice] = 'Beer was successfully created.'
format.html { redirect_to beer_url(@beer) }
else
format.html { render :action => quot;newquot; }
end
end
end

end


More about Rails
• There’s much more about Rails to explore
• But that’s another topic
• We’ve touched upon some appealing
aspects
• Development is much quicker!
• But ...


Java Perspective

• What if ...
• Java provides where Ruby doesn’t?
• What about ...
• deploying Rails apps?


Java and Ruby


JRuby


JRuby
• Java implementation of Ruby
• Major advantages:
• Java libraries can be used with Ruby syntax
• Deploy Rails apps on Java app servers
• via WAR ﬁles


Invoking Java from Ruby
require 'java'

m = java.util.HashMap.new

m.put quot;Streamquot;, quot;Rubyquot;
m.put quot;Topicquot;, quot;JRubyquot;

iter = m.keySet.iterator
while iter.hasNext
key = iter.next
puts quot;#{key}=#{m.get(key)}quot;
end


Some JRuby Capabilities

• Implement Java interfaces via import or impl

• Extend Java classes
• Use Ruby methods on Java collections
courtesy of Ruby mixins
• Use JavaUtilities.extend_proxy to add
methods to Java types


Java DOM and XSLT*
require 'java'
require 'stringio'

TransformerFactory = javax.xml.transform.TransformerFactory
StreamSource = javax.xml.transform.stream.StreamSource
StreamResult = javax.xml.transform.stream.StreamResult

f = TransformerFactory.new_instance
t = f.new_transformer
StreamSource.new(java.io.FileReader.new(ARGV[1]))
s = StringIO.new
t.transform StreamSource.new(java.io.FileReader.new(ARGV[0])),
StreamResult.new(org.jruby.util.IOOutputStream.new(s))
puts s.string

* see Ola Bini’s book

JRuby on Rails


JRuby on Rails:
JDBC
• Download JDBC
driver development:
adapter: jdbc
driver: com.mysql.jdbc.Driver

• Add to CLASSPATH url: jdbc:mysql://localhost/
beers_development
username: test

•
password: test
Conﬁgure config/
database.yml

• Update config/ require 'jdbc_adapter'

environment.rb Rails::Initializer.run do |config|


Deploying JRuby on
Rails Applications
• Option 1:
• Pack of Mongrels inside one JVM
• Option 2:
• Bundle as WAR and deploy
inside Tomcat


Pack of Mongrels
• Familiar to Rails developers
• Install mongrel_jcustler Gem

• Conﬁgure pack using mongrel_rails

• Start pack using mongrel_rails

• Conﬁgure load balancing proxy
support and virtual host in Apache


Deploying via a WAR
• Install GoldSpike plug-in in Rails app
• Conﬁgure app with correct driver for
JDBC connections (in config/war.rb)

• Use jruby rake task to create WAR
• Deploy WAR
• Conﬁgure Apache


Installing GoldSpike

jruby script/plugin install -x
svn://rubyforge.org/var/svn/jruby-extras/trunk/rails-integration/plugins/goldspike


JDBC Driver Conﬁg

maven_library 'mysql', 'mysql-connector-java', '5.0.4'


Create WAR

jruby -S rake war:standalone:create


Deploy WAR

cp beers.war $TOMCAT_HOME/webapps


Conclusion
• Ruby offers some interesting beneﬁts
• Ruby on Rails offers quick development
for CRUD web apps
• JRuby enables Ruby apps to call Java code
• JRuby enables deployment of Rails apps
via WAR ﬁles to Java app servers


Resources
• Ola Bini. Practical JRuby on Rails Web
2.0 Projects. Apress, 2007
• David A. Black. Ruby for Rails.
Manning, 2006
• http://buildr.rubyforge.org
• http://www.capify.org
• http://jruby.codehaus.org


Resources (ctd.)
• Martin Fowler. RailsConf2007 => http://
martinfowler.com/bliki/
RailsConf2007.html
• Martin Fowler. Using the Rake Build
Language => http://martinfowler.com/
articles/rake.html
• Hal Fulton. The Ruby Way. Addison-
Wesley, 2007


Resources (ctd)
• David Heinemeier Hansson. Sun
surprises at RailsConf Europe 2007
=> http://www.loudthinking.com/
posts/11-sun-surprises-at-railsconf-
europe-2007
• Brian Marick. Everyday Scripting with
Ruby: For Teams, Testers and You.
Pragmatic Programmers, 2006


Resources (ctd)
• http://mongrel.rubyforge.org
• Keith Pitty. Why is Ruby such a good
language for Rails? => http://
keithpitty.org/presentations/ruby/
WhyRubyForRails.pdf
• http://rubyonrails.org
• http://www.tiobe.com/tpci.htm


Photo Credits
• Bored Cow: http://flickr.com/
photos/kevincollins/122302356/
• Leopard getting ready to drop out
of tree: http://flickr.com/photos/
at_large/399149551/
• Origami heart: http://flickr.com/
photos/teagrrl/4802517/


Thanks for listening!

http://keithpitty.com


Why would a Java shop want to use Ruby?

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