boot.rb

$LOAD_PATH << $APP_LOAD_PATH  #set the load path from the APP_LOAD_PATH binding

if $RACK_ENV == 'production'
  ENV['GEM_PATH'] = "#{File.join($RULE_SERVER_HOME, 'vendor/jruby/1.8')}:#{File.join($TORQUEBOX_HOME, 'jruby/lib/ruby/gems/1.8')}"
  ENV['GEM_HOME'] = File.join($RULE_SERVER_HOME, 'vendor/jruby/1.8')
else
  puts 'Using global GEM_HOME directory.'
end

require 'rubygems'
require 'java'

engine.rb

java_import "javax.script.ScriptContext"
java_import "javax.script.ScriptEngine"
java_import "javax.script.ScriptEngineManager"
java_import "javax.script.ScriptException"
java_import "java.io.FileNotFoundException"
java_import "javax.script.Bindings"
java_import "javax.script.SimpleBindings"
java_import "java.io.FileReader"
java_import "java.io.Reader"

def create_jruby_engine
  # this means that we take all responsibility for concurrency
  java.lang.System.setProperty("org.jruby.embed.localcontext.scope", 'singlethread')

  m = ScriptEngineManager.new()
  e = m.getEngineByName("jruby")

  bindings = SimpleBindings.new()
  bindings.put("TORQUEBOX_HOME", ENV['TORQUEBOX_HOME'])
  bindings.put("RACK_ENV", ENV['RACK_ENV'])
  bindings.put("INSTANCE_ID", ENV['INSTANCE_ID'])

  app_load_path = File.expand_path('../..', File.dirname(__FILE__))
  bindings.put("APP_LOAD_PATH", app_load_path)

  yield e, bindings

  e
end

def eval_file(engine, relative_path, bindings)
  file = File.expand_path(relative_path, __FILE__)
  reader = FileReader.new(file)
  engine.eval(reader, bindings)
end

def load_gems(engine, gems)
  s = gems ? gems.map do |gem|
    gem_name = gem.gsub(/ (\(.+\))?\z/, "").strip
    version = gem =~ /\((.*\s?.+)\)\z/ ? $1 : ">= 0"
    "gem '#{gem_name}', '#{version}'; require '#{gem_name}'; "
  end : []
  engine.eval("begin; #{s.join('; ')} rescue => e; puts e.message; end")
end

e = create_jruby_engine do |e, bindings|  
  eval_file(e, "../../engine/embedded/boot.rb", bindings)
  load_gems(e, gems)
end

e.invokeFunction(:do_something, params)