Interface HttpSesssionBindingListenner extends EventListener;
api文档关于这个接口的介绍是：使对象在被绑定到会话或从会话中取消对它的绑定时得到通知。该对象通过 HttpSessionBindingEvent 对象得到通知。这可能是 servlet 编程人员显式从会话中取消绑定某个属性的结果（由于会话无效，或者由于会话超时）。
这个接口有两个方法：1. void valueBound(HttpSessionBindingEvent event) 2. void valueUnbound(HttpSessionBindingEvent event) .
HttpSesssionBindingListenner 继承自EventListener接口，而EventListener接口是这样的：
public interface EventListener ：A tagging interface that all event listener interfaces must extend. 这句话表明EventListener只是个标记接口，和Cloneable,Serializable类似；这个接口只是用来标记该事件监听器的接口。具体使用如下：
javabean实现HttpSesssionBindingListenner 接口并实现它的两个方法，当对象别绑定到会话时或从会话中取消对他的绑定时得到通知，即调用该javabean对象的这两个方法。
1 import javax.servlet.http.HttpSessionBindingEvent; 2 import javax.servlet.http.HttpSessionBindingListener; 3 public class User implements HttpSessionBindingListener{ ????4 ????private String name; 5 ????private String pwd; 6 ????private UserList userList=UserList.getInstance(); ????7 ????public User() { 8 ????????// TODO Auto-generated constructor stub 9 ????}10 ????public User(String name, String pwd) {11 ????????super();12 ????????this.name = name;13 ????????this.pwd = pwd;14 ????}15 ????public String getName() {16 ????????return name;17 ????}18 ????public void setName(String name) {19 ????????this.name = name;20 ????}21 ????public String getPwd() {22 ????????return pwd;23 ????}24 ????public void setPwd(String pwd) {25 ????????this.pwd = pwd;26 ????}27 ????@Override28 ????public String toString() {29 ????????return "User [name=" + name + ", pwd=" + pwd + "]";30 ????}31 ????public void valueBound(HttpSessionBindingEvent arg0) {32 ????????// TODO Auto-generated method stub33 ????????this.userList.addUser(this);34 ????????System.out.println(this.name+"上线了！目前在线人数为："+this.userList.getCount());35 ????}36 ????public void valueUnbound(HttpSessionBindingEvent arg0) {37 ????????// TODO Auto-generated method stub38 ????????this.userList.removeUser(this);39 ????????System.out.println(this.name+"下线了！目前在线人数为："+this.userList.getCount());40 ????}41 }工具类：
1 import java.util.ArrayList; 2 import java.util.List; 3 public class UserList { ????4 ????private static ?UserList userList=new UserList(); 5 ????private List<User> list=new ArrayList<User>(); 6 ????private UserList() { 7 ????????// TODO Auto-generated constructor stub 8 ????} 9 ????public static ?UserList getInstance(){10 ????????return userList;11 ????}12 ????public void addUser(User user){13 ????????list.add(user);14 ????}15 ????public void removeUser(User user){16 ????????list.remove(user);17 ????}18 ????public int getCount(){19 ????????return list.size();20 ????}21 }以上就是关于 HttpSesssionBindingListenner 接口的学习。。。。。。
HttpSessionBindingListener的学习
原文地址：http://www.cnblogs.com/YsirSun/p/7846413.html