JRuby Quick Start

This quick start is using the experimental "complete" jar, which allows the JRuby distribution to be contained in a single jar and extracted easily.

  • Download jruby complete jar
  • In a command shell, go to a directory where you wish to install JRuby.
  • Extract a JRuby install from it: 
    java -jar jruby-complete-0.9.8.jar --command extract jruby
  • Now we have a JRuby install. Go ahead and download an additional jar that we'll need later for running Rubygems and Rails with ActiveRecord-JDBC; put this in the "lib" directory of your new JRuby install.
  • To use the install, we can simply add /parent/dir/jruby/bin to our path and continue. 
    # UNIX
PATH=/parent/dir/jruby/bin:$PATH
rem Windows
set PATH=c:\parent\dir\jruby\bin;%PATH%
  • We now have "jruby", "jirb", and "gem" commands available to us. You can also access any bin-directory-installed script with the "--command" argument to JRuby. 
    jirb
irb(main):001:0> quit
jruby --command irb
irb(main):001:0> quit
  • JIRB stands for JRuby IRB. IRB as you probably know is Interactive RuBy. We can do regular Ruby things in irb, but using JRuby's java integration, we can also create and use Java objects. Enter the following code, one line at a time, in IRB. 
    require 'java'

frame = javax.swing.JFrame.new "Hello JIRB"
frame.set_default_close_operation javax.swing.JFrame::EXIT_ON_CLOSE
frame.set_size 200, 200

button = javax.swing.JButton.new "Press me"
frame.content_pane.add button

frame.visible = true
# frame shows with the button

class Clicked < java.awt.event.ActionListener
  def actionPerformed(e)
    @count ||= 0
    @count += 1
    e.source.text = "You pressed me #@count times."
  end
end

button.add_action_listener Clicked.new
# button is clickable and shows count
  • You install Rails just like with regular Ruby, with Rubygems. You may wish to disable RDoc generation to speed up the install process as it is quite a bit slower in JRuby. 
    jruby --command gem install rails --include-dependencies --no-ri --no-rdoc
  • Once Rails is installed, we can generate a play application: 
    jruby --command rails playground
...
cd playground
  • And we can start Ruby's embedded web server WEBrick: 
    jruby script/server
=> Booting WEBrick...
=> Rails application started on http://0.0.0.0:3000
=> Ctrl-C to shutdown server; call with --help for options
[2007-02-23 14:20:21] INFO  WEBrick 1.3.1
[2007-02-23 14:20:21] INFO  ruby 1.8.5 (0) [java]
[2007-02-23 14:20:22] INFO  WEBrick::HTTPServer#start: pid=15244180 port=3000
  • And visit http://localhost:3000 in a browser. JRuby on Rails is up and running!
  • We can use ActiveRecord-JDBC to create a database-backed JRuby on Rails application. A little setup is needed. 
    jruby --command gem install ActiveRecord-JDBC --no-ri --no-rdoc
  • We also need a bit of custom code in environment.rb to load in the JDBC adapter. See the ActiveRecord-JDBC documentation and Running Rails with ActiveRecord JDBC for details. 
    # config/environment.rb: Put this before the Rails initializer
require 'rubygems'
gem 'ActiveRecord-JDBC'
require 'jdbc_adapter'
  • Add this bit of config to your database.yml to use HSQLDB: 
    # config/database.yml
development:
  adapter: jdbc
  username: sa
  password:
  driver: org.hsqldb.jdbcDriver
  url: jdbc:hsqldb:db/dev.db
  • Now let's create a model: 
    jruby script/generate model post
  • Edit the migration, add the table structure, and run the migration. 
    # db/migrations/001_create_posts.rb
  def self.up
    create_table "posts", :force => true do |t|
      t.column :title, :string, :limit => 100
      t.column :updated_on, :datetime
      t.column :content, :text
    end
  end

  def self.down
    drop_table "posts"
  end

    jruby --command rake db:migrate
  • In progress, more to come. I'm still troubleshooting portions of the script -- there currently appear to be some issues with HSQL and migrations.