## 概述 servlet2.3后增加的新功能,运行在服务器端的程序,先于与之相关的servlet或者JSP页面之前运行. ## 作用 过滤请求和响应. ## 使用步骤 1. 实现一个filter接口. 2. 重写所有方法. 3. 注册filter. 4. 绑定路径. ## web.xml配置 也可以不用配置:在filter注解中加入以下的配置. ~~~ urlPatterns = "/show" ~~~ ~~~ <filter> <filter-name>show</filter-name> <filter-class>com.like.ShowFilter</filter-class> </filter> <filter-mapping> <filter-name>show</filter-name> <url-pattern>/show</url-pattern> </filter-mapping> ~~~ ~~~ @WebFilter(filterName = "ShowFilter") public class ShowFilter implements Filter { public void destroy() { } public void doFilter(ServletRequest req, ServletResponse resp, FilterChain chain) throws ServletException, IOException { chain.doFilter(req, resp); } public void init(FilterConfig config) throws ServletException { } } ~~~