X-Sendfile middleware for JRuby-Rack 1.0.8 or greater

jruby-rack-x-sendfile.rb

class JRubyRackXSendfile
  def initialize(app)
    @app = app
  end

  def call(env)
    result, headers, body = @app.call(env)
    if headers['X-Sendfile']
      [result, headers, File.new(headers.delete('X-Sendfile'))]
    else
      [result, headers, body]
    end
  end
end

http://stackoverflow.com/questions/5904693/sendfile-on-jruby-jrack-tomcat

...make sure the controller sets the header when sending a file so this middleware picks it up.

To clarify, for example:

module ApplicationHelper
  def set_sendfile_header(path_to_file)
    request.headers['X-Sendfile'] = path_to_file.to_s
  end
end

class MyController < ApplicationController
  def download
    set_sendfile_header params[:file]
  end
end