在web开发中，我们经常用到过滤器Filter，用来对所有web资源：例如Jsp, Servlet, 静态图片文件或静态 html 文件等进行拦截，Jave自定义过滤器Filter,从而实现一些特殊的功能,

下面展示一些 内联代码片。

// A code block
系统中因为要做活动，做一个问卷调查，需求：针对系统管理员创建的一个活动，针对发布后，用户登录系统后，弹框弹问卷活动，必须回答调查，不然不能操作启动的任何页面，可以用jave 的过滤器很好的实现这个功能，实现的代码如下，

// An highlighted block
public class TaskPublishFilter implements Filter
{private String taskUrl;private List<String> excludeList = new ArrayList();@Overridepublic void init(FilterConfig filterConfig) throws ServletException{String taskUrl = filterConfig.getInitParameter("taskUrl");this.taskUrl = taskUrl == null ? "task/publish/items" : taskUrl;String excludeActions = filterConfig.getInitParameter("excludeUrls");if (excludeActions != null) {String[] tokenizer = StringUtils.tokenizeToStringArray(excludeActions, ",; \t\n");this.excludeList.addAll(Arrays.asList(tokenizer));}}protected boolean isNeedValid(HttpServletRequest httpRequest) {String requestUrl = WebUtils.getRequestUrl(httpRequest);if (requestUrl != null) {String[] staticResources = new String[]{".jpg", ".png", ".jpeg", ".gif", ".js", ".css", ".html", ".htm", ".swf", ".doc", ".docx", ".xls", ".xlsx", ".jar", ".class"};String[] var7 = staticResources;int var6 = staticResources.length;String tmp;for(int var5 = 0; var5 < var6; ++var5) {tmp = var7[var5];if (StringUtils.endsWithIgnoreCase(requestUrl, tmp)) {return false;}}if (!requestUrl.startsWith(this.taskUrl) && !requestUrl.startsWith("theme/default")) {if (this.excludeList.isEmpty()) {return true;} else {Iterator var8 = this.excludeList.iterator();do {if (!var8.hasNext()) {return true;}tmp = (String)var8.next();} while(!requestUrl.endsWith(tmp) && !MatcherUtils.matchStrings(tmp, requestUrl));return false;}} else {return false;}} else {return true;}}@Overridepublic void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException{HttpServletRequest httpRequest = (HttpServletRequest) request;HttpServletResponse httpResponse = (HttpServletResponse) response;HttpSession session = httpRequest.getSession(true);Object object = HttpSessionHolder.getAttribute(AuthenticationSessionKey.AUTHENTICATED_USER);if (!isNeedValid(httpRequest) || object == null || ValidationUtils.isSuperUser() || ValidationUtils.isManager() || !ValidationUtils.isSupplier()){chain.doFilter(httpRequest, httpResponse);}else{PortalUser user = (PortalUser) object;Object taskPublish = session.getAttribute(SessionKeyConstants.TASK_PUBLISH_TIPS);if (taskPublish != null){chain.doFilter(request, response);}else{TaskPublishService taskPublishService = SpringContextHolder.getBean("taskPublishService", TaskPublishService.class);TaskPublish taskPublishTop1 = taskPublishService.getTaskPublishTop1();if (taskPublishTop1 == null || !taskPublishTop1.getEnabled()){chain.doFilter(request, response);}else{TaskPublishItemService taskPublishItemService = SpringContextHolder.getBean("taskPublishItemService", TaskPublishItemService.class);List<TaskPublishItem> taskPublishItems = taskPublishItemService.queryTaskPublishItemList(taskPublishTop1.getId(), user.getUserId());if (CollectionUtils.isNotEmpty(taskPublishItems)){HttpSessionHolder.setAttribute(SessionKeyConstants.TASK_PUBLISH_TIPS, taskPublishTop1);chain.doFilter(request, response);}else{String contextPath = httpRequest.getContextPath();httpResponse.sendRedirect(contextPath + "/" + this.taskUrl);}}}}}@Overridepublic void destroy(){}
}