Double bundle deploy. Nice trick to run two seperate Gemfiles for one project and deploy it with style.

deploy.rb

require "bundler/capistrano"
after "deploy:finalize_update",   "bundle:jruby_install"

namespace :bundle do
  desc "Install bundle environment for jruby"
  task :jruby_install do
    old_current_release = fetch(:current_release)
    set :bundle_dir, File.join(fetch(:shared_path), 'jruby_bundle')
    set :current_release, File.join(fetch(:current_release), 'lib/jruby_daemon')
    install
    set :current_release, old_current_release
  end
end