uri_validator.rb

require 'net/http'
class UriValidator < ActiveModel::EachValidator
  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 = { check_response: true, format: /(\A\z)|(\A(http|https):\/\/[a-z0-9]+([\-\.]{1}[a-z0-9]+)*\.[a-z]{2,5}(:[0-9]{1,5})?([\/].*)?\z)/ix}
    configuration.update(options)
    if value =~ configuration[:format]
      if configuration[:check_response]
        begin # check header response
          case Net::HTTP.get_response(URI.parse(value))
            when Net::HTTPSuccess, Net::HTTPRedirection then true
            else object.errors.add(attribute, configuration[:message] || "is not responding") and false
          end
        rescue # Recover on DNS failures..
          object.errors.add(attribute, configuration[:message] || "is not responding") and false
        end
      end
    else
      object.errors.add(attribute, configuration[:message] || :invalid) and false
    end
  end
end