Connecting the Worlds of Java and Ruby with JRuby

Connecting
Java and Ruby
Nick Sieger :: December 14, 2010
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Slides: http://j.mp/ey-jruby-connecting

Connecting
Java and Ruby
Nick Sieger :: December 14, 2010

JRuby: Bridge Between Two Worlds

http://www.ﬂickr.com/photos/hb2/288721287/

Bridges facilitate...

Cross-
Movement Collaboration Trading
pollination

Bridge from Ruby to Java

http://www.ﬂickr.com/photos/orbitaljoe/4038901965/ http://www.ﬂickr.com/photos/the_rev/2295096211/

Bridge from Java to Ruby

http://www.ﬂickr.com/photos/design-dog/1268749868/

Bridge from Enterprise to Cloud

http://www.ﬂickr.com/photos/nzdave/347532488/ http://www.ﬂickr.com/photos/ancawonka/65927497/

Bridge from Legacy to Greenfield

http://www.flickr.com/photos/cobalt/318394059/ http://www.flickr.com/photos/13010608@N02/2441101211/

Ruby
Dynamic language of the cloud

A word about
scripting...
It’s for kiddies.

Ruby: Dynamic,
Object-Oriented

http://www.ﬂickr.com/photos/listenmissy/4869202176/

Ruby: Duck-Typing

def area(width = 10, height = 2 * width)
width * height
end

p area # => 200
p area 5 # => 50
p area 5, 20 # => 100
p area "10", 4 # => ?

Ruby: Duck-Typing

p area "10", 4 # => "10101010"

# From Ruby API docs:

# String#*(num)
#
# Returns a new String containing num copies of
# the receiver.
#
# "Ho! " * 3 #=> "Ho! Ho! Ho! "

area true, false
# => NoMethodError: undefined method `*' for
# true:TrueClass

Ruby: Flexible Syntax

def set_options(env, opts)
end

set_options(:production, {"caching" => "on", "debug" => "false"})

set_options(:production, "caching" => "on", "debug" => "false")

set_options :production, {"caching" => "on", "debug" => "false"}

set_options :production, "caching" => "on", "debug" => "false"

Ruby: Blocks

list = [1, 2, 3, 4]

list.each {|n| puts n }
Ruby
list.each do |n|
puts n
end

List<Integer> list = Arrays.asList(1, 2, 3, 4);

Java for (Integer n : list) {
System.out.println(n);
}

Ruby: Blocks

list.shuffle!
# => [3, 1, 4, 2]
Ruby
p list.sort {|a, b| b <=> a }
# => [4, 3, 2, 1]

Collections.shuffle(list);

Collections.sort(list, new Comparator<Integer>() {
public int compare(Integer a, Integer b) {
Java return b > a ? 1 : (b < a ? -1 : 0);
}
});

System.out.println(list);

Ruby: Blocks

File.open(__FILE__) do |file|
file.each_line do |line|
Ruby puts line
end
end

BufferedReader file =
new BufferedReader(new FileReader("Blocks.java"));
try {
String line;
while ((line = buf.readLine()) != null) {
Java System.out.println(line);
}
} finally {
file.close();
}

Ruby: Open Classes

msg = "Scramble this so you can't read it!"
msg.rot13!

# => NoMethodError: undefined method `rot13!' for
# "Scramble this so you can't read it!":String

Ruby: Open Classes

class String
def rot13!
0.upto(length - 1) do |i|
case self[i]
when ?a..?z
self[i] = ?a + ((self[i] - ?a) + 13) % 26
when ?A..?Z
self[i] = ?A + ((self[i] - ?A) + 13) % 26
end
end
self
end
end

Ruby: Open Classes

puts msg.rot13!
# => "Fpenzoyr guvf fb lbh pna'g ernq vg!"
puts msg.rot13!
# => "Scramble this so you can't read it!"

Ruby: Interactive

$ irb
irb(main):001:0> list = [1, 2, 3, 4]
=> [1, 2, 3, 4]
irb(main):002:0> list.shuffle.map {|x| x + rand(10)}.sort
=> [6, 7, 11, 13]
irb(main):003:0> list
=> [1, 2, 3, 4]

Ruby: Interactive

irb(main):004:0> require 'irb/completion'
=> true
irb(main):005:0> list.<TAB>
Display all 138 possibilities? (y or n)
irb(main):005:0> list.d<TAB>
list.delete list.delete_at list.delete_if list.detect
list.display list.drop list.drop_while list.dup

Ruby: Developer Happiness

=

Testing in Ruby

RSpec
http://rspec.info/ http://cukes.info/

Ruby: Summary

• Organize code the way you want
Dynamic and Open • Associate behavior with the correct class
• No more “Util” classes

• Express code intent succinctly
Flexible • Strip away unnecessary ceremony

• Try out code and get instant feedback
Interactive • Learn by doing

• Productivity gains lead to increased pleasure
Happy • Enjoy crafting clean code

Rails
Dynamic framework of the cloud

Rails: Opinionated Framework

Request- Convention Defaults
Place for
based over with
everything
MVC Conﬁguration Choices

Rails: Place for All Your Code

application code
conﬁguration & environments
routes (URL structure)

database migrations

static assets
(images, stylesheets, javascript)

tests

Rails: Request-based MVC

Request Routing Controller
Model
Action Action
ActiveRecord
Dispatch Controller

View
Database
Response ActionView

Rails: Convention over Conﬁguration

URL GET /people

resources :people
Routing
#=> people#index

# app/controllers/people_controller.rb
class PeopleController < ApplicationController
def index
Controller
@people = Person.all
end
end

# app/models/person.rb
Model class Person < ActiveRecord::Base
end

View app/views/people/index.html.erb

Rails: Defaults with Choices

Default Alternatives

DataMapper, MongoMapper,
ORM ActiveRecord Sequel, Any object with
ActiveModel

HAML, Builder XML,
View Templates ERb Markaby, RedCloth (Textile),
BlueCloth (Markdown)

JavaScript Framework Prototype jQuery

MySQL, PostgreSQL, Oracle,
Database SQLite3
more via JRuby + JDBC

Test Framework Test::Unit RSpec, Cucumber

Why Rails?

COMPARING JVM WEB
FRAMEWORKS
Matt Raible
http://raibledesigns.com

Images by Stuck in Customs - http://www.ﬂickr.com/photos/stuckincustoms
© 2010, Raible Designs
© 2010 Raible Designs

http://j.mp/raible-jvm-frameworks

Why Rails?

Consider...

Information Available
Project Development
Books, skilled
maturity speed
Docs developers

Installing Rails
INSTALL gem install rails

Rails: New Application

$ rails new coolapp -m http://jruby.org
create
create README
create Rakefile
...

Rails: Dependencies with Bundler

$ cd coolapp

$ bundle install
Fetching source index for http://rubygems.org/
Using rake (0.8.7)
Using abstract (1.0.0)
...
Using rails (3.0.3)
Your bundle is complete!

Rails: Generate Scaffolding

$ rails generate scaffold person email:string password:string
invoke active_record
create db/migrate/20101214020707_create_people.rb
create app/models/person.rb
invoke test_unit
create test/unit/person_test.rb
create test/fixtures/people.yml
route resources :people
...

Rails: Migrate Database

$ rake db:migrate
(in /Users/nicksieger/Projects/rails/coolapp)
== CreatePeople: migrating ===========================
-- create_table(:people)
-> 0.0040s
-> 0 rows
== CreatePeople: migrated (0.0040s) ==================

Rails: Start Dev Server

$ rails server
=> Booting WEBrick
=> Rails 3.0.3 application starting in development on http://0.0.0.0:3000
=> Call with -d to detach
=> Ctrl-C to shutdown server
[2010-12-13 20:11:28] INFO WEBrick 1.3.1
[2010-12-13 20:11:28] INFO ruby 1.8.7 (2010-12-10) [java]
[2010-12-13 20:11:28] INFO WEBrick::HTTPServer#start: pid=21022 port=3000

Rails: Console

$ rails console
Loading development environment (Rails 3.0.3)
irb(main):001:0> Person.create :email => "nsieger@engineyard.com", :password => "rails"
=> #<Person id: 1, email: "nsieger@engineyard.com", password: "rails", created_at:
"2010-12-14 02:21:11", updated_at: "2010-12-14 02:21:11">

https://joindiaspora.com/

https://github.com/diaspora/diaspora

Routes

# config/routes.rb (abbreviated)
Diaspora::Application.routes.draw do
# ...
resources :photos, :except => [:index]

#...
root :to => 'home#show'
end

Rails: RESTful Routes

Verb Path Action Used for

display a list of all
GET /photos index
photos
return an HTML form for
GET /photos/new new
creating a new photo

POST /photos create create a new photo

GET /photos/:id show display a specific photo

GET /photos/:id/edit edit
editing a photo

PUT /photos/:id update update a specific photo

DELETE /photos/:id destroy delete a specific photo

Rails: RESTful Routes

Verb Path Action Used for

display a list of all
GET /photos index
:except => [:index] photos
GET /photos/new new
creating a new photo

POST /photos create create a new photo

GET /photos/:id show display a specific photo

GET /photos/:id/edit edit
editing a photo

PUT /photos/:id update update a specific photo

DELETE /photos/:id destroy delete a specific photo

Controller

# app/controllers/photos_controller.rb (abbr.)
class PhotosController < ApplicationController
respond_to :html
respond_to :json, :only => :show

def show
@photo = current_user.find_visible_post_by_id params[:id]
# ...
respond_with @photo
end
end

Model

# app/models/photo.rb (abbreviated)
class Photo < Post
include MongoMapper::Document

require 'carrierwave/orm/mongomapper'
mount_uploader :image, ImageUploader

key :caption, String
key :status_message_id, ObjectId

belongs_to :status_message

validate :ownership_of_status_message

before_destroy :ensure_user_picture
end

View

Rendering photo list

HAML View

-# app/views/people/show.html.haml (abbr.)
.span-15.last
%h4
= t('_photos')
= render 'photos/index', :photos => @posts

-# app/views/photos/_index.html.haml (abbr.)
#thumbnails.span-15.last
- for photo in photos
= link_to photo.url(:thumb_medium), photo_path(photo)

Rendered HTML View

<div class='span-15 last'>
<h4>
photos
</h4>
<div class='span-15 last' id='thumbnails'>
<a href="/photos/4d0694d..."><img src="/uploads/images/..." /></a>
<a href="/photos/4d06949..."><img src="/uploads/images/..." /></a>
<a href="/photos/4d068b2..."><img src="/uploads/images/..." /></a>
</div>
</div>

Rails: Summary

• No wasting time deciding where to put something
Place for Everything &
• Shared conventions get team members up to
Conventions speed quickly

• No wasted effort getting started
Defaults with Choices • Easy to add/change components later

• Development: “code and reload”
Environments • Test: disposable data
• Production: cache and optimize

• Mature framework, frequent updates
Community • Rich catalog of plugins
• Rails programmers are in-demand

Getting JRuby

OS How to get

•http://jruby.org/download
All •Ruby Version Manager (RVM)
http://rvm.beginrescueend.com/

Windows •Installer from http://jruby.org/download

Mac OS X
•Homebrew - brew install jruby
•MacPorts - port install jruby
Ubuntu/Debian •apt-get install jruby (may not be up-to-date,
may need multiverse)
Fedora/RHEL/Centos •yum install jruby (may not be up-to-date)

Gentoo •emerge dev-java/jruby (may be old)

http://wiki.jruby.org/JRubyDistributions

Using JRuby

$ jruby script.rb Run a standalone script

$ jruby -S gem ... Run Rubygems, IRB, or an installed
gem (e.g, rake or rails)

$ jruby -J-Xmx1G ... Pass arguments to the JVM

$ jruby --help Get help
$ jruby --properties

Access Java from JRuby

require 'java'
require 'rubygems'
require 'flying_saucer'

java_import org.xhtmlrenderer.pdf.ITextRenderer

document = <<-HTML
<html><body><h1>Hello Flying Saucer!</h1></body></html>
HTML

File.open("doc.pdf", "wb") do |out|
renderer = ITextRenderer.new
renderer.set_document_from_string document
renderer.layout
renderer.create_pdf out.to_outputstream
end

system("open doc.pdf")

Tip: jruby -S gem install flying_saucer to try this example.


$ jruby saucer.rb


require 'java'

Loads Java Integration


require 'rubygems'
require 'flying_saucer'

Loads Flying Saucer classes from Rubygems


java_import org.xhtmlrenderer.pdf.ITextRenderer

Imports ITextRenderer class


Ruby renderer = ITextRenderer.new

Java ITextRenderer renderer = new ITextRenderer();

Create new ITextRenderer


Ruby renderer.set_document_from_string document

Java renderer.setDocumentFromString(document);

Set up the document


File.open("doc.pdf", "wb") do |out|
...
renderer.create_pdf out.to_outputstream
end

Create PDF with explicit conversion
from Ruby IO to Java OutputStream

Integrating into Rails

Mime::Type.register 'application/pdf', :pdf

Register PDF mime type in Rails


class PhotosController
private
def pdf_to_string
io = StringIO.new
content = render_to_string
renderer = ITextRenderer.new
renderer.set_document_from_string(content)
renderer.layout
renderer.create_pdf(io.to_outputstream)
io.string
end
end


class PhotosController
def index
@photos = Photos.all
respond_to do |format|
format.html
format.pdf do
send_data pdf_to_string, :filename => pdf_name + ".pdf",
:type => 'application/pdf', :disposition => 'inline'
end
end
end
end


http://example.com/photos HTML view of photo listing

http://example.com/photos.pdf Inline PDF of photo listing

Rails 3 and JRuby

http://weblog.rubyonrails.org/2010/8/29/rails-3-0-it-s-done

Rails Performance

http://github.com/wycats/rails-simple-benches

rails-simple N = 10,000 rails-simple N = 10,000
15000 120000
ruby 1.9.2 ruby 1.9.2
12500 jruby-head client 100000 jruby-head client
10000 jruby-head server 80000 jruby-head server

7500 60000
5000 40000
2500 20000
0 0
partial_100 coll_100 uniq_100 diff_100
ad

x

1

al

10

10
de

e_

rti

_

ll_
he

at

al
pa
in

co
er

rti
pl
ov

pa
m
te

JRuby Deployment

Ruby servers WAR ﬁles PaaS

WEBrick GlassFish EY AppCloud

GF Gem Tomcat AppEngine

Trinidad JBoss SteamCannon

Warbler

INSTALL gem install warbler

• Create a Java EE .war ﬁle from a Rails application
• “Looks like Java” to the ops staff

deploy
Rails
warble app.war to java
app
appserver

JRuby-Rack Servlet Filter

/home.jsp:
Servlet JSP
dispatch
pass-thru
/home.jsp /home/index:
JRuby-Rack 404
RackFilter
doFilter
On 404:
/home/index
Rails or any /home/index:
Rack-based Rails
application Home-
Controller

Hybrid Rails/Java Webapp

ActionDispatch

Rails
MVC ActionController/ActionView

ActiveModel

Java JDBC SOAP
POJOs DataSource interface

Tools

http://www.jetbrains.com/ruby/

http://redcareditor.com/

http://netbeans.org/

Enterprise
Software
Evolving and adapting long-running
projects with legacy codebases

http://en.wikipedia.org/wiki/File:Sagrada_Familia_01.jpg

Sagrada Família, Barcelona, Spain

http://www.ﬂickr.com/photos/mgrenner57/263392884/

1970s early 2000s
http://www.ﬂickr.com/photos/gonzalvo/4257293127/

http://www.flickr.com/photos/koocheekoo/38407225/

http://www.flickr.com/photos/27649557@N07/5000528445/
passion
facade

nativity
facade

scaffolded interior

http://www.flickr.com/photos/gpaumier/446059442/ http://www.flickr.com/photos/ilm/12831049/

http://en.wikipedia.org/wiki/File:Ryugyong_Hotel_October_2010.jpg
2010
Ryugyuong Hotel,
North Korea
2005
http://en.wikipedia.org/wiki/File:Ryugyong_Hotel_-_May_2005.JPG

http://en.wikipedia.org/wiki/File:ExteiorShearTruss.jpg

seismic retroﬁt

http://en.wikipedia.org/wiki/File:ExtReenfDetail.jpg

http://en.wikipedia.org/wiki/File:Szkieleteor_in_krakow.JPG

Szkieletor,
Kraków, Poland

http://www.ﬂickr.com/photos/bazylek/3194294047/

Built Environment Metaphor

Metaphor Use Ruby, JRuby, and Rails to...

• Build a new facade faster with modern technology
Sagrada Familia • Scaffold portions of the application during refactoring

• Revive a languishing project by putting a new face on it
Ryugyong Hotel

• Reinforce business rules with a DSL
Seismic retroﬁt • Harden security around an existing application

Szkieletor • Find novel uses for otherwise abandoned code

JRuby Stories: LinkedIn Signal

• High-volume social networking application
• http://www.infoq.com/articles/linkedin-scala-jruby-voldemort
• http://blog.linkedin.com/2010/09/29/linkedin-signal/

JRuby Stories: Tracker

• Protecting the world from terrorists!
• Export Control workﬂow system
• Used by US State dept. and other countries
• JRuby, Rails and legacy Java
• http://trackernet.org
• Making the World Safe For Democracy
• David Bock, Arild Shirazi
• http://vimeo.com/16270284

JRuby Events

• JRubyConf 2009
• free event following RubyConf
• ~200 attendees
• JRubyConf 2010
• standalone conference
• 150 attendees
• JRuby meetups in SF Bay Area
• http://www.meetup.com/SF-Bay-
Area-JRuby-Meetup/

JRuby on AppCloud

JRuby +
AppCloud

Resources

• Contact me: Nick Sieger – nsieger@engineyard.com
• These slides: http://j.mp/ey-jruby-connecting
• JRuby.org – http://jruby.org/
• JRubyConf 2010 videos
• http://j.mp/jrubyconf-2010-videos
• EY Blog: Resources for Getting Started with Ruby on Rails
• http://j.mp/ey-getting-started-rails
• Rails for Zombies
• http://railsforzombies.org/

Zero to Rails 3
Virtual Training
January 24-27, 2011
http://www.eventbee.com/view/zero-to-rails-3
training@engineyard.com

Immediately following (optional):
Engine Yard AppCloud Demo
with Danish Khan
15-20 minute overview of AppCloud

Connecting the Worlds of Java and Ruby with JRuby

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