handle_conditional_get!

# File actionpack/lib/action_controller/response.rb, line 46
      def handle_conditional_get!
        if body.is_a?(String) && (headers['Status'] ? headers['Status'][0..2] == '200' : true)  && !body.empty?
          self.headers['ETag'] ||= %("#{Digest::MD5.hexdigest(body)}")
          self.headers['Cache-Control'] = 'private, max-age=0, must-revalidate' if headers['Cache-Control'] == DEFAULT_HEADERS['Cache-Control']

          if request.headers['HTTP_IF_NONE_MATCH'] == headers['ETag']
            self.headers['Status'] = '304 Not Modified'
            self.body = ''
          end
        end
      end