Devoxx%202008%20Tutorial

JRuby in Action

Ruby, Rails, GUIs, and More

Except where otherwise noted, the content of this presentation is licensed under
the Creative Commons AttributionShare Alike 3.0 United States License (http://creativecommons.org/licenses/bysa/3.0/us/).

The JRuby Guys
● Charles Oliver Nutter and Thomas Enebo
● JRuby for 4+ years
● Sun Microsystems for 2+ years
● JVM languages

Ruby
● Dynamically typed
● Pure object-oriented
● C-language implementation
● Green threads
● “Fast enough” == “a bit slow”
● 1.8.6/7 is current
● 1.9 in development
● Focus on performance, character encodings

JRuby
● Ruby on the JVM
● Nearly complete Ruby compatibility
● Interop with Java libraries
● Improvements on original
● Native threading
● Faster by most measurements
● 1.1.6 this week (RC1 out now)
● 1.8.6 compatible, 1.9 in progress

Ruby Tutorial
● Walkthrough of all the key Ruby features
● Interactive! Please jump in with questions
● Free-form, live-coded
● Ruby is fun, Ruby tutorial should be fun!

Modules

Object

MyGreatClass

class MyGreatClass < Object
…
end

Modules
Object

MyGreatModule

MyGreatClass

include MyGreatModule
end

Modules
Class
class

Object Object
class meta class

MyGreatClass MyGreatClass
class meta class

extend MyGreatModule
end

Modules
Object
Object
Meta class

MyGreatModule

MyGreatClass
MyGreatClass
Meta class

extend MyGreatModule
end

Singletons

Object

my_object MyGreatClass

class MyGreatClass
end

my_object = MyGreatClass.new

Singletons
Object

MyGreatClass

MyGreatClass
my_object
singleton class

class MyGreatClass
end

my_object = MyGreatClass.new
class << my_object
end

More Cool Ruby: FFI
● Foreign Function Interface
● Call C libraries from Ruby code
● Works on Ruby and JRuby
● Map simple types, structs, callbacks
● DSL for function binding

JVMScript (working title)
● A DSL for generating JVM bytecode
● Multiple Ruby techniques employed
● Goal: structured assembly for JVM

What is Ruby on Rails?
● A Full-stack MVC web development framework
● Open Source (MIT), Many Contributors
● Written in Ruby
● Single-Threaded design (2.2 has MT-mode)
● First released in 2004 by David Heinemeier Hansson
● Super-hyped! :) :(

Rails Precepts
● Convention over Configuration
● Why punish the common cases?
● Encourages standard practices
● Everything simpler and smaller
● Don't Repeat Yourself (DRY)
● Framework written around minimizing repetition
● Repetitive code harmful to adaptability
● Agile Development Environment
● No recompile, deploy, restart cycles
● Simple tools to generate code quickly
● Testing built into framework

Why Rails?
● Greatly simplified web development
● “Less Rails code than Java app configuration”
● Instant applications: working code in minutes
● Makes small apps trivial to create
● Ruby is an excellent language
● Still growing in popularity in leaps and bounds

The Rails Stack
● ActiveRecord
● ORM on steroids
● ActionPack
● View and controller support
● ActiveResource
● Restful resources
● Actionmailer
● Email
● Activesupport
● Unicode, json, miscellaneous helpers

Rails Demo

Let's write a simple blog app

JRuby on Rails
● Java is Everywhere
● Every OS/Hardware platform you can think of
● Probably already on a server near you
● Less political resistance
● “JRuby is just another Jar file”
● No need to install additional software on your servers
● Wider database support
● Decent performance

JRuby on Rails (Warbler)
● Java-style deployment to Application Server
● Bundles a Rails application into a WAR file
● Hand WAR file to production staff
● Rails App deployed!

Rack

http://wiki.jruby.org/wiki/JRuby_Rack

JRuby on Rails (GlassFish v3 gem)
● Entire App Server in a 4Mb gem
● Ruby-style deployment to GF Application Server
● gem install glassfish
● glassfish <Rails app dir>
● Configurable number of listeners all in one process
● Under active development

GlassFish

Parts is Parts
● Script Java technology you need into your Rails app
● Call “legacy” Java from existing project
● Get additional choices

Swing GUI in JRuby
● Builder approach (ex: Rubeus)
● Sort of a “model 1” 1998 JSP approach
● Great for simple forms
● Difficult for long-term, large apps
● Tool-driven approach (ex: MonkeyBars)
● Tool manages UI layout
● Logic is MVC-driven
● UI and logic evolved, maintained separately
● Easier to scale to large apps

Devoxx%202008%20Tutorial

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