ActiveRecord validator for URLs

model.rb

require 'uri_validator'

class SomeModel < ActiveRecord::Base
  validates :url, :presence => true, :uri => { :format => /(^$)|(^(http|https):\/\/[a-z0-9]+([\-\.]{1}[a-z0-9]+)*\.[a-z]{2,5}(:[0-9]{1,5})?([\/].*)?$)/ix }
end

uri_validator.rb

require 'net/http'

# Thanks Ilya! http://www.igvita.com/2006/09/07/validating-url-in-ruby-on-rails/
# Original credits: http://blog.inquirylabs.com/2006/04/13/simple-uri-validation/
# HTTP Codes: http://www.ruby-doc.org/stdlib/libdoc/net/http/rdoc/classes/Net/HTTPResponse.html

class UriValidator < ActiveModel::EachValidator
  TIMEOUT_IN_SECONDS = 4
  def validate_each(object, attribute, value)
    raise(ArgumentError, "A regular expression must be supplied as the :format option of the options hash") unless options[:format].nil? or options[:format].is_a?(Regexp)
    configuration = { :message => "is invalid or not responding", :format => URI::regexp(%w(http https)) }
    configuration.update(options)
    
    if value =~ configuration[:format]
      begin # check header response
        Rack::MiniProfiler.step("UriValidator with http.head") do
          uri = URI.parse(value)
          http = Net::HTTP.new(uri.host, uri.port)
          http.continue_timeout = TIMEOUT_IN_SECONDS
          http.open_timeout = TIMEOUT_IN_SECONDS
          http.read_timeout = TIMEOUT_IN_SECONDS
          if uri.scheme == "https"
            http.use_ssl = true
            http.verify_mode = OpenSSL::SSL::VERIFY_NONE
            http.ssl_timeout = TIMEOUT_IN_SECONDS
          end
          case http.head(uri.request_uri)          
            when Net::HTTPSuccess, Net::HTTPRedirection then true
            else object.errors.add(attribute, configuration[:message]) and false
          end
        end
      rescue # Recover on DNS or timeout failures..
        object.errors.add(attribute, configuration[:message]) and false
      end
    else
      object.errors.add(attribute, configuration[:message]) and false
    end
  end
end