Servlet 监听器

• 分类
  • ServletContextListener
  • ServletContextAttributeListener
  • HttpSessionListener
  • HttpSessionAttributeListener
  • HttpSessionActivationListener
• web.xml 注册在过滤器后面，servlet前面

  • <listener>
    <listener-class>cn.listen.MyListener</listener-class>
    </listener>

• 自定义

  • public class MyListener implements ServletContextListener {
        public void contextDestroyed(ServletContextEvent sce) {
            System.out.println("die");
        }
        public void contextInitialized(ServletContextEvent sce) {
            System.out.println("init");
        }
     
        // 当过滤器被销毁时自动执行
        public void destroy(){
            System.out.println("Filterdestroyed");
        }
        // 当拦截的时候
        public void doFilter(request,response,chain){
            System.out.println("doFilter");
            System.out.println("放行目标资源");
            chain.doFilter(request,response);
            System.out.println("目标已经放行");
        }
        // 初始化的时候
        public void init(FilterConfig config){
            System.out.println("FilterInited");
        }
    }