JRuby Whirlwind Tour
Ola Bini
JRuby Core Developer
ThoughtWorks Studios

About me
• Ola Bini
• From Stockholm, Sweden
• Works for ThoughtWorks Studios in London
• Programming language nerd

What is JRuby
• Java implementation of the Ruby language
• Current version 1.0
• Based on Ruby 1.8.5
• Started in 2001
• Currently 6 core developers
• Open Source, about 30 contributors
• ThoughtWorks offers
commercial support

Why JRuby?
• Performance
• Native threading
• Native Unicode support
• Interpreted, compiled, mixed-mode, AOT, JIT
• Java library integration (JDBC, XML, etc)
• Enterprise acceptance

Demo:
Interactive JRuby

Compatibility
• Ruby has no official specification
• ... and no complete suite of tests
• We take what’s available for JRuby
• Existing suites (BFTS, Rubicon, ruby_test)
• Our own suite
• Other tests (Rubinius)
• Application test suites (RSpec, Rails,
RubyGems)

JRuby runtime modes
• Interpreted
• Standard mode, fully implemented
• Compilation
• Not complete yet
• AOT
• JIT - Hot swap method implementations

JRuby on Rails
• JRuby runs Rails very well
• Improved deployment story
• JDBC database connections
• Performance
• Integrate with Java infrastructure

ActiveRecord-JDBC
• ActiveRecord adapter for JDBC drivers
• Supports MySQL, Postgres, Oracle, Derby,
MS SQL Server, HSQLDB, and more
• Easy to add new databases

Goldspike
• Support for packaging and serving Rails
WAR files
• Rails plugin, adds Rake tasks
• Includes a RailsServlet
• Can deploy to any compliant Java application
server
• Can run directly with embedded Jetty

Demo?
JRuby on Rails

Mingle
• Agile Project Intelligence
• First commercial JRuby on Rails application
• Originally choose JRuby for SVN plugins
• Later used JRuby for:
• Derby (embedded Java database)
• Protecting source code
• Easy bundling

Mingle+JRuby lessons
• Mingle was originally developed in MRI
• A LARGE test suite helps the migration
• Running the Mingle test suite under JRuby is
slightly slower than on MRI
• ... but the actual application performs and
scales better
• Java Integration is MUCH easier than C
extensions

YARV
• Yet Another Ruby VM
• Ruby 2.0
• JRuby have a simple YARVMachine
• JRuby also have a simple YARV compiler
• Work going on to replace interpreted mode
with YARV interpretation instead

Rubinius
• JRuby has a simple Rubinius machine
• Not support for all Rubinius bytecodes
• Why
• Compatibility
• Experimentation
• Alternative to YARV for interpretation?

Testing
• RSpec
• RBehave
• Test::Unit
• Mocha
• All works fine on JRuby
• ... and can be used on Java classes too

Swing
• Cheri
• By JRuby Core Developer Bill Dortch
• Nice Ruby wrapper around Swing
• Profligacy
• By Zed Shaw
• Uses ASCII-pictures create layouts (LEL)

Profligacy example
[ label_1 | label3 ]
[ (300,300)*text1 | (150)people ]
[ <label2 |_ ]
[ message | buttons ]

Rubiq
• Lisp layer on top of JRuby
• Transforms to JRuby AST
• ... and lets JRuby execute it
• Rubiq is _very_ new (three days)
• But will soon provide several interesting
stuff

Rubiq features
• Macros
• Read macros (used to implement regexp
syntax, for example)
• Pure lexical scoping
• Lambdas transparently transforms to blocks
or Proc.new depending on location
• Will not support most Ruby syntax
• Principle of least Lisp-surprise

Under the hood
• JRuby::ast_for(“1+1”) #-> Java AST
• JRuby::ast_for { 1+1 } #-> Java AST
• JRuby::compile(“1+1”) #-> CompiledScript
• CompiledScript.inspect_bytecode
• JRuby::runtime
• JRuby::reference(“str”)

A JRuby future
• Ruby objects right now descends from
org.jruby.RubyObject
• Planning to make most of the lightweight
objects with behavior attached
• Finish the compiler
• Make YARV or Rubinius standard
interpretation
• Focus on surrounding projects

24 September, ‘07

Resources
• JRuby: www.jruby.org
• ThoughtWorks Studios:
studios.thoughtworks.com
• Profligacy: ihate.rubyforge.org
• JRuby-extras: jruby-extras.rubyforge.org
• Rubiq: rubiq.googlecode.com
• My blog: ola-bini.blogspot.com

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