* iterable is empty.
   *
   * <p><b>Java 8+ users:</b> the {@code Stream} equivalent to this method is {@code
   * stream.collect(MoreCollectors.toOptional()).orElse(defaultValue)}.
   *
   * @throws IllegalArgumentException if the iterator contains multiple elements
   */
  @ParametricNullness
  public static <T extends @Nullable Object> T getOnlyElement(

     *
     * @return HTML response for login page or redirect to admin interface
     */
    protected HtmlResponse getHtmlResponse() {
        return getUserBean().map(this::redirectByUser).orElse(asHtml(virtualHost(path_Login_IndexJsp)));
    }

    /**
     * Redirects an authenticated user to the appropriate admin interface based on their roles.

            throws IOException, ServletException {
        final RequestManager requestManager = ComponentUtil.getRequestManager();
        if (!requestManager.findUserBean(FessUserBean.class).map(user -> user.hasRoles(acceptedRoles)).orElse(Boolean.FALSE)) {
            response.sendError(HttpServletResponse.SC_UNAUTHORIZED, "Unauthorized access: " + request.getServletPath());
            return;
        }

        try {

            form.seqNo = (Long) entity.remove(fessConfig.getIndexFieldSeqNo());
            form.primaryTerm = (Long) entity.remove(fessConfig.getIndexFieldPrimaryTerm());
        }).orElse(() -> {
            throwValidationError(messages -> messages.addErrorsCrudCouldNotFindCrudTable(GLOBAL, form.id), this::asListHtml);
        });
        saveToken();
        return asEditHtml();
    }

    /**

            return redirectToLogin();
        }

        Map<String, Object> doc = null;
        try {
            doc = searchHelper.getDocumentByDocId(form.docId, queryFieldConfig.getCacheResponseFields(), getUserBean()).orElse(null);
        } catch (final Exception e) {
            logger.warn("Failed to request: {}", form.docId, e);
        }
        if (doc == null) {

        final OptionalThing<FessUserBean> userBean = getUserBean();
        activityHelper.logout(userBean);
        final String redirectUrl = userBean.map(user -> ComponentUtil.getSsoManager().logout(user)).orElse(null);
        fessLoginAssist.logout();
        userInfoHelper.deleteUserCodeFromCookie(request);
        if (StringUtil.isNotBlank(redirectUrl)) {
            return HtmlResponse.fromRedirectPathAsIs(redirectUrl);
        }

        }
        buf.append("; charset=");
        final String enc;
        if (encoding == null) {
            enc = LaRequestUtil.getOptionalRequest().map(HttpServletRequest::getCharacterEncoding).orElse(Constants.UTF_8);
        } else {
            enc = encoding;
        }
        buf.append(enc);
        final HttpServletResponse response = LaResponseUtil.getResponse();

            return redirectToLogin();
        }

        final Map<String, Object> doc =
                searchHelper.getDocumentByDocId(form.docId, queryFieldConfig.getResponseFields(), getUserBean()).orElse(null);
        final String url = DocumentUtil.getValue(doc, fessConfig.getIndexFieldThumbnail(), String.class);
        if (StringUtil.isBlank(form.queryId) || StringUtil.isBlank(url) || !thumbnailSupport) {
            // 404

     */
    @SuppressWarnings("unchecked")
    public static <T> T getObject(final String name) {
        return LaRequestUtil.getOptionalRequest().map(req -> (T) req.getAttribute(name)).orElse(null);
    }

    /**
     * Sets an error in the current request with the specified status code and message.
     *
     * @param statusCode The HTTP status code
     * @param message The error message
     */

                if (host.getValue2().equalsIgnoreCase(headerValue)) {
                    return func.apply(host.getValue3());
                }
            }
            return defaultValue;
        }).orElse(defaultValue);
    }

    /**
     * Gets all configured virtual host paths.
     *
     * @return An array of virtual host paths
     */
    public String[] getVirtualHostPaths() {