JSP-JSP监听器

一、//在web.xml中配置listener

<listener>
<listener-class>cn.news.lisener.UserLisener</listener-class>
</listener>

二、在com.wu.listener包下写一个UserListener类

HttpSessionBindingListener接口

valueBound(HttpSessionBindingEvent event)

当对象被添加到session时，由容器调用该方法来通知对象，无返回值

valueUnbound(HttpSessionBindingEvent event)

当对象从session中清除时，由容器调用该方法通知对象，无返回值

public class UserListener implements HttpSessionBindingListener {
//session生效
public void valueBound(HttpSessionBindingEvent arg0) {
Statistics.USER_ONLINE_STATISTICS++;

}
public void valueUnbound(HttpSessionBindingEvent arg0) {
Statistics.USER_ONLINE_STATISTICS--;
}
}

//在UserServlet

UserListener ul = new UserListener();
if (user != null) {
// 如果正确，保存用户的状态信息
if (user.getPwd().equals(upwd)) {
System.out.println("登录成功");
HttpSession session = request.getSession();
session.setAttribute("loginuser", user.getUname());
session.setAttribute("isadmin", user.getIsadmin());
session.setAttribute("ul", ul);
response.sendRedirect(request.getContextPath() + "/index.jsp");