require 'rack'
require 'json'
require "active_support/core_ext/hash/conversions"

class HelloWorld
  def call(env)
    req = Rack::Request.new(env)

    if req.content_type =~ /json/
      resp = env.to_json
    else
      resp = env.to_xml
    end

    return [200, {"Content-Type" => req.content_type}, [resp]]
  end
end

Rack::Handler::WEBrick.run(
  HelloWorld.new,
  :Port => 9000
)