JSP+SERVLET实现后登陆用户挤掉之前登录用户
项目简介
该项目是一个很简单的测试项目,主要实现了用户登录时对于同一个用户名后一用户登录挤掉前一用户的功能,虽然项目很简单,但是实现的功能却是很有参考价值的。
功能示例
首先进入登录页面(用户名wuyang,密码不输):
然后第一个用户登录:
接着登录第二个用户:
第二个用户登录后第一个用户的页面会立即弹出提示,并转到登录页面(无刷新):
原理简介
主要是servlet中对用户登录时的处理,servlet中维护了用户和sessionId的关系以及用户和session的关系,保存在两个map中,当用户登录时会向map中新增一条记录,如果发现map中已经有了该用户,则将该用户对应的记录删掉,注意是将map中的记录删掉而不是将session销毁,然后在该session中放入给用户提示的信息,再将新用户的信息放入map中。再页面中需要不断的验证session中有没有提示信息,如果有则说明已经被挤掉,有一点要注意的是,jsp中获取到的session中的Attribute是不会自动更新的,也就是说如果不刷新页面,即使servlet已经向该用户的session中放入了提示信息,页面中也不会得到的,所以这里我们需要用Ajax的方式不断的向服务器发送请求以获取session中用户提示信息的动态,一旦发现session中有提示信息,就给出提示。
项目代码
(注:jquery-1.4.2.min.js请自己下载)
login.jsp
<%@ page language="java" import="java.util.*"pageEncoding="gbk"%>
<%
String path =request.getContextPath();
String basePath =request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
String msg =(String)(request.getAttribute("msg")==null?"":request.getAttribute("msg"));
//System.out.println("msg:"+msg);
%>
<!DOCTYPE HTMLPUBLIC "-//W3C//DTD HTML 4.01Transitional//EN">
<html>
<head>
<base href="<%=basePath%>">
<title>My JSP 'index.jsp' starting page</title>
<meta http-equiv="pragma"content="no-cache">
<meta http-equiv="cache-control"content="no-cache">
<meta http-equiv="expires"content="0">
<meta http-equiv="keywords"content="keyword1,keyword2,keyword3">
<meta http-equiv="description"content="This is mypage">
<!--
<link rel="stylesheet" type="text/css"href="styles.css">
-->
</head>
<script type="text/javascript">
function show(){
if('<%=msg%>'!=''){
alert('<%=msg%>');
}
}
</script>
<body style="text-align: center"onload="show()">
<form action="login.do"method="post">
<table border="1">
<tr>
<tdalign="center"colspan="2">
<h3>用户登录</h3>
</td>
</tr>
<tr>
<td aling="right">
用户名
</td>
<td align="left">
<inputtype="text"id="userName"name="userName">
</td>
</tr>
<tr>
<td aling="right">
密 码
</td>
<td align="left">
<inputtype="text"id="password"name="password">
</td>
</tr>
<tr>
<td align="center" colspan="2">
<inputtype="submit"value="登录">
<inputtype="reset"value="重置">
</td>
</tr>
</table>
</form>
</body>
</html>
main.jsp
<%@ page language="java" contentType="text/html;charset=gbk"pageEncoding="gbk"%>
<html>
<head>
<title>主页</title>
<Meta http-equiv="Content-Type"Content="text/html;Charset=gbk">
<meta http-equiv="pragma"content="no-cache">
<meta http-equiv="cache-control"content="no-cache">
<meta http-equiv="expires"content="0">
<meta http-equiv="keywords"content="keyword1,keyword2,keyword3">
<meta http-equiv="description"content="This is mypage">
<script type="text/javascript"src="./jquery-1.4.2.min.js"></script>
</head>
<%
response.setHeader("Pragma","No-cache");
response.setHeader("Cache-Control","No-cache");
response.setDateHeader("Expires", -1);
response.setHeader("Cache-Control","No-store");
String userName = "";
userName = (String)(session.getAttribute("userName")==null?"":session.getAttribute("userName"));
%>
<script type="text/javascript">
var int;
var userMsg = '';
var i =0;
function checkUserOnline(){
$.ajax({
type:"post",
url:"getUserMsg.do",
dataType : "text",
success:function(data){userMsg = data;},
error:function(){
alert("获取用户信息失败!");
clearInterval(int);
reLogin();
}
});
if(userMsg=='null'||userMsg==''){
return;
}else{
alert(userMsg);
clearInterval(int);
reLogin();
}
}
function reLogin(){
window.location = "reLogin.do";
}
function toLogin(){
window.location = "./login.jsp";
}
function checkLogin(){
int = setInterval("checkUserOnline()",500);
}
</script>
<body onload="checkLogin()">
<%
if(!"".equals(userName)){
out.print("登陆成功!<br/>用户名:<span id='userName'>"+userName+"</span><br/><inputtype='button' value='重登陆' onclick='reLogin();'/>");
}
%>
</body>
</html>
user.LoginServlet
package user;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.HashMap;
import java.util.Map;
importjavax.servlet.ServletException;
importjavax.servlet.http.HttpServlet;
importjavax.servlet.http.HttpServletRequest;
importjavax.servlet.http.HttpServletResponse;
importjavax.servlet.http.HttpSession;
importjavax.servlet.http.HttpSessionEvent;
importjavax.servlet.http.HttpSessionListener;
public class LoginServlet extends HttpServletimplements HttpSessionListener{
/**
* 用户和Session绑定关系
*/
public static final Map<String,HttpSession>USER_SESSION=new HashMap<String, HttpSession>();
/**
* seeionId和用户的绑定关系
*/
public static final Map<String, String>SESSIONID_USER=new HashMap<String,String>();
/**
* 实现HttpSessionListener接口监听,监听session的销毁和创建事件
*/
public void sessionDestroyed(HttpSessionEvent se) {
StringsessionId=se.getSession().getId();
//当前session销毁时删除当前session绑定的用户信息
//同时删除当前session绑定用户的HttpSession
USER_SESSION.remove(SESSIONID_USER.remove(sessionId));
System.out.println("销毁session:"+sessionId);
}
public void sessionCreated(HttpSessionEvent arg0) {
String sessionId = arg0.getSession().getId();
System.out.println("创建session:"+sessionId);
}
/**
* 用户登录时的处理
* 处理一个账号同时只有一个地方登录的关键
* @paramrequest
*/
public static voiduserLoginHandle(HttpServletRequest request){
//当前登录的用户
StringuserName=request.getParameter("userName");
//当前sessionId
String sessionId=request.getSession().getId();
//删除当前sessionId绑定的用户,用户--HttpSession
USER_SESSION.remove(SESSIONID_USER.remove(sessionId));
//删除当前登录用户绑定的HttpSession
HttpSession session=USER_SESSION.remove(userName);
if(session!=null){
SESSIONID_USER.remove(session.getId());
session.removeAttribute("userName");
session.setAttribute("userMsg", "您的账号已经在另一处登录了,你*下线!");
}
}
/**
* 用户登录
*/
protected void service(HttpServletRequest request,
HttpServletResponseresponse) throws ServletException,IOException {
//获取请求命令
request.setCharacterEncoding("gbk");
String servletPath = request.getServletPath();
String uri = servletPath.substring(1,servletPath.lastIndexOf(".do"));
//System.out.println("uri:"+uri);
try{
if("login".equals(uri)){//登录
HttpSession session=request.getSession();
String userName=request.getParameter("userName");
Stringpassword=request.getParameter("password");
if(userName!=null&&!"".equals(userName.trim())){
//登录成功
if(login(userName, password)){
//处理用户登录(保持同一时间同一账号只能在一处登录)
userLoginHandle(request);
//添加用户与HttpSession的绑定
USER_SESSION.put(userName.trim(), session);
//添加sessionId和用户的绑定
SESSIONID_USER.put(session.getId(), userName);
System.out.println("用户["+userName+"]已上线");
session.setAttribute("userName", userName);
session.removeAttribute("userMsg");
response.sendRedirect("main.jsp");
}else{
System.out.println("用户["+userName+"]登录失败");
request.setAttribute("msg","登录失败,请重新登录");
//response.sendRedirect("login.jsp");
request.getRequestDispatcher("login.jsp").forward(request,response);
//注意:上面的代码如果没有放在try中,将无法传递参数msg
}
}else{
System.out.println("用户["+userName+"]登录失败");
request.setAttribute("msg","登录失败,请重新登录");
//response.sendRedirect("login.jsp");
request.getRequestDispatcher("login.jsp").forward(request,response);
//注意:上面的代码如果没有放在try中,将无法传递参数msg给jsp
}
}else if("reLogin".equals(uri)){//重登陆
HttpSession session=request.getSession();
String userName = (String)session.getAttribute("userName");
if(session!=null){
USER_SESSION.remove(SESSIONID_USER.remove(session.getId()));
session.invalidate();
}
if(userName!=null&&!"".equals(userName))System.out.println("用户["+userName+"]下线");
response.sendRedirect("login.jsp");
}else if("getUserMsg".equals(uri)){
HttpSession session=request.getSession();
String CONTENT_TYPE = "text/html; charset=GBK";
response.setContentType(CONTENT_TYPE);
PrintWriter out = response.getWriter();
//System.out.println(session.getAttribute("userMsg"));
out.print(session.getAttribute("userMsg"));
}
}catch(Exception e){
e.printStackTrace();
PrintWriter out= response.getWriter();
out.print("服务器内部出错!");
}
}
//对比用户输入的信息是否合法,从而判断是否登录成功
private boolean login(String userName,String password){
return "wuyang".equals(userName);
}
}