过滤器(Filter)是一种类实现了java.servlet.Filter接口 写Filter的步骤: 1.创建一个类:implements java.servlet.Filter 2.自动生成三个方法: public void init(FilterConfig filterconfig) throw ServleException public void doFilter(ServletRequest request,ServletResponse response) public void destroy() 3在WebRoot/WEB-INF/web.xml文件中配置Filter <filter> <filter-name>FilterServlet</filter-name> <filter-class>com.servlet.zz.web.FilterServlet</filter-class> </filter> <filter-mapping> <filter-name>FilterServlet</filter-name> <url-pattern>/*</url-pattern>
</filter-mapping>
监听器
监听器也提供了好几个接口,用来监听不同的事件:
ServletContextListener接口:监听web应用的启动和关闭
ServletContextAttributeListener接口:监听application对象(ServletContext类的实例对象)内的值得变化
ServletRequestListener接口:监听request对象(ServletRequest类的实例对象)
ServletRequestAttributeListener接口:监听request对象(ServletRequest类的实例对象)内值的变化
HttpSessionListener接口:监听session对象(HttpSession类的实例对象)的开始和结束
HttpSessionAttribute接口:监听session对象(HttpSession类的实例对象)