code: private void requestAuthorization(HttpServletResponse resp) throws IOException {
  
          // Authorisation is required for the requested action.
          resp.setHeader(CmsRequestUtil.HEADER_WWW_AUTHENTICATE, "Basic realm=\"" + BASIC_REALM + "\"");
  
          resp.sendError(HttpServletResponse.SC_UNAUTHORIZED);
      }
docs: Sends a response back to authenticate the user.<p>
  
  @param resp the servlet response we are processing
  
  @throws IOException if errors while writing to response occurs