* @param form the cache form containing document ID and highlight query
     * @return ActionResponse containing the cached document content or error redirect
     */
    @Execute
    public ActionResponse index(final CacheForm form) {
        validate(form, messages -> {}, () -> asHtml(virtualHost(path_Error_ErrorJsp)));
        if (isLoginRequired()) {
            return redirectToLogin();
        }

        Map<String, Object> doc = null;