Listener感知监听器HttpSessionBindingListener直接由类实现

简介：

当javaBean实现了HttpSessionBindingListener接口后，就能自动感知自己是否被添加到session中。并且这个实现不需要在webx.xml中进行注册。

代码实现：

创建User类实现HttpSessionBindingListener接口：

package demoListener;

import java.util.Objects;

import javax.servlet.http.HttpSessionBindingEvent;
import javax.servlet.http.HttpSessionBindingListener;

public class User implements HttpSessionBindingListener {
    private String username;
    private String passwoed;
    public User() {
        super();
    }
    public User(String username, String passwoed) {
        super();
        this.username = username;
        this.passwoed = passwoed;
    }
    public String getUsername() {
        return username;
    }
    public void setUsername(String username) {
        this.username = username;
    }
    public String getPasswoed() {
        return passwoed;
    }
    public void setPasswoed(String passwoed) {
        this.passwoed = passwoed;
    }
    @Override
    public int hashCode() {
        return Objects.hash(passwoed, username);
    }
    @Override
    public boolean equals(Object obj) {
        if (this == obj)
            return true;
        if (obj == null)
            return false;
        if (getClass() != obj.getClass())
            return false;
        User other = (User) obj;
        return Objects.equals(passwoed, other.passwoed) && Objects.equals(username, other.username);
    }
    @Override
    public String toString() {
        return "User [username=" + username + ", passwoed=" + passwoed + "]";
    }
    @Override
    public void valueBound(HttpSessionBindingEvent event) {
        System.out.println("已绑定！！");
    }
    @Override
    public void valueUnbound(HttpSessionBindingEvent event) {
        System.out.println("已解绑！！");
    }
    
}

创建两个JSP页面，一个添加session，一个移除session：

addSession.jsp:

<%@page import="demoListener.User"%>
<%@taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c"%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>title</title>
</head>
<body>
<%
    User user = new User();
    session.setAttribute("user", user);
%>
<h1>添加session的JSP</h1>
</body>
</html>

removeSession:

<%@taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c"%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>title</title>
</head>
<body>
<%
    session.removeAttribute("user");
%>
<h1>移除session的JSP</h1>
</body>
</html>