怎么在Java项目中利用servlet实现一个自动登录退出功能？相信很多没有经验的人对此束手无策，为此本文总结了问题出现的原因和解决方法，通过这篇文章希望你能解决这个问题。
UserDao.java从数据库中查询用户名与密码
//登录
public User login(User user) throws SQLException {
QueryRunner qr = new QueryRunner(DataSourceUtils.getDataSource());
String sql = "select from user where username = ? and password = ?";
return qr.query(sql, new BeanHandler<User>(User.class),user.getUsername(),user.getPassword());
}
UserService.java
public User login(User user){
try {
return ud.login(user);
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return null;
}UserServlet.java实现登录功能
//登录
public void login(HttpServletRequest request,
HttpServletResponse response) throws IOException, IllegalAccessException, InvocationTargetException, ServletException{
Map<String,String[]> map = request.getParameterMap();
User user = new User();
BeanUtils.populate(user,map);
if (map.get("autoLogin")!=null){
Cookie username = new Cookie("username", map.get("username")[0]);
username.setMaxAge(6060);
Cookie password = new Cookie("password", map.get("password")[0]);
password.setMaxAge(60*60);
response.addCookie(username);
response.addCookie(password);
}
user = us.login(user);
if (user != null){
request.getSession().setAttribute("user", user);
response.sendRedirect("/ShopStore/default.jsp");
}
else{
request.setAttribute("message", "用户或密码错误！");
request.getRequestDispatcher("/login.jsp").forward(request, response);
}
}工具类:AutoLoginFilter.java用来实现自动登录
package com.yinhe.web.filter;
import java.io.IOException;
import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.Cookie;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import com.yinhe.bean.User;
import com.yinhe.service.UserService;
public class AutoLoginFilter implements Filter{br/>@Override
public void doFilter(ServletRequest request, ServletResponse response,
FilterChain chain) throws IOException, ServletException {
HttpServletRequest req = (HttpServletRequest)request;
HttpServletResponse resp = (HttpServletResponse)response;
//是否已登录
if (req.getSession().getAttribute("user") == null){//如果已登录，则啥都不干
//判断cookie中有没有账户密码
Cookie[] cookies = req.getCookies();
if (cookies != null){
String username = "";
String userpass = "";
for (Cookie cookie : cookies) {
if (cookie.getName().equals("username")){//找到感兴趣的cookie
username = cookie.getValue();
}
if (cookie.getName().equals("password")){//找到感兴趣的cookie
userpass = cookie.getValue();
}
}
UserService us = new UserService();
User user = new User();
user.setUsername(username);
user.setPassword(userpass);
if (us.login(user) != null){
req.getSession().setAttribute("user", user);
}
}
}
chain.doFilter(request, response);br/>}
@Override
public void init(FilterConfig filterConfig) throws ServletException {
// TODO Auto-generated method stubbr/>}
@Override
public void destroy() {
// TODO Auto-generated method stub
}
}前台:login.jsp此单选框被选中下次访问即为自动登录
<div class="checkbox">
<label> <input type="checkbox" name="autoLogin" > 自动登录
</label> <label> <input
type="checkbox" > 记住用户名
</label>
</div>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
<title>系统首页</title>
<style>
#nav{
height: 88px;
padding: 5px 200px;
background-color: aquamarine;
}
#logo{
float: left;
}
#userinfo{
float: right;
height: 50px;
line-height: 80px;
}
#container{
background-color: aqua;
height: 800px;
margin: 2px 200px;
font-size: xx-large;
text-align: center;
}
</style>
</head>
<body>
<div id="nav">
<div id="logo">
<img src="csdn-logo.png" width="180" height="88">
</div>
<div id="userinfo">
<%-- 不推荐使用
<%
String loginUser = (String) request.getAttribute("loginUser");
if (loginUser != null){
out.println(loginUser);
}else {
%>
<a href="login.jsp" rel="external nofollow" rel="external nofollow" rel="external nofollow" >登录</a><a>/注册</a>
<%
}
%>
--%>
<%
String loginUser = (String) session.getAttribute("loginUser");
if (loginUser != null){
out.println(loginUser);
out.println("<a href='logoutServlet'>退出</a>");
}else {
%>
<a href="login.jsp" rel="external nofollow" rel="external nofollow" rel="external nofollow" >登录</a><a>/注册</a>
<%
}
%>
</div>
</div>
<div id="container">主页内容
<a href="info.jsp" rel="external nofollow" >Python——画一棵漂亮的樱花树（不同种樱花+玫瑰+圣诞树喔）</a>
</div>
</body>
</html>
login.jsp
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
<title>登录</title>
<style>
tr{
height:50px;
}
td{
text-align: center;
}
</style>
</head>
<body>
<%
String msg = (String)request.getAttribute("msg");
%>
<%
if(msg != null){
out.print(msg);
}
%>
<form action="myServlet02" method="get">
<h2 align="center">登录</h2>
<table width="500" border="1" cellspacing="0" cellpadding="0" align="center">
<tr>
<td>账号：</td>
<td><input type="text" name="username" /></td>
</tr>
<tr>
<td>密码：</td>
<td><input type="password" name="password" /></td>
</tr>
<tr>
<td colspan="2"><input type="submit" value="登录" /></td>
</tr>
</table>
</form>
</body>
</html>info.jsp
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
<title>Title</title>
<style>
#nav{
height: 88px;
padding: 5px 200px;
background-color: aquamarine;
}
#logo{
float: left;
}
#userinfo{
float: right;
height: 50px;
line-height: 80px;
}
#container{
background-color: aqua;
height: 800px;
margin: 2px 200px;
font-size: xx-large;
text-align: center;
}
</style>
</head>
<body>
<div id="nav">
<div id="logo">
<img src="csdn-logo.png" width="180" height="88">
</div>
<div id="userinfo">
<%
String loginUser = (String) session.getAttribute("loginUser");
if (loginUser != null){
out.println(loginUser);
out.println("<a href='logoutServlet'>退出</a>");
}else {
%>
<a href="login.jsp" rel="external nofollow" rel="external nofollow" rel="external nofollow" >登录</a><a>/注册</a>
<%
}
%>
</div>
</div>
<div id="container">
主页内容
</div>
</body>
</html>Servlet02.java
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
import java.io.IOException;br/>@WebServlet("/myServlet02")
public class Servlet02 extends HttpServlet {
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
//修改编码
request.setCharacterEncoding("utf-8");//请求过来的编码是亨达返佣www.kaifx.cn/broker/hantecglobal.htmlutf-8
response.setContentType("text/html;charset=utf-8");//响应出去的内容，为网页编码utf-8
//获取表单数据
String username = request.getParameter("username");
String password = request.getParameter("password");
//验证
if("aaa".equals(username) && "123".equals(password)){
//跳转(请求转发 请求重定向)
//重定向：两次请求，不能在request作用域中共享数据。
//如果要在两次请求或多次请求之间，进行数据共享，需要用session
//使用session步骤
//获取session
HttpSession session = request.getSession();//如果存在已有的session，则直接返回，否则会创建一个新的，返回。
//HttpSession session = request.getSession(true);//同上
//HttpSession session = request.getSession(false);//如果存在已有的session，则直接返回，否则返回null。
//在session的作用域保存数据，供后续请求使用
session.setAttribute("loginUser",username);
response.sendRedirect("index.jsp");
/ 多个页面不推荐使用请求转发
request.setAttribute("loginUser",username);
request.getRequestDispatcher("index.jsp").forward(request,response);
/
}else {
//转发：一次请求，可以在request作用域中，共享数据
request.setAttribute("msg","<script>alert('登录失败！');</script>");
// response.sendRedirect("login.jsp");
request.getRequestDispatcher("login.jsp").forward(request,response);
}
}
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
doPost(request, response);
}
}LogoutServlet.java
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
import java.io.IOException;br/>@WebServlet("/logoutServlet")
public class LogoutServlet extends HttpServlet {
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
//退出系统
//获取session
HttpSession session = request.getSession();
//删除session
session.removeAttribute("loginUser");
//跳转到登录页面/首页
response.sendRedirect("index.jsp");
}
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
doPost(request, response);
}
}web.xml
<?xml version="1.0" encoding="UTF-8"?> <web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd" version="3.1"> <welcome-file-list> <welcome-file>index.jsp</welcome-file> </welcome-file-list> </web-app>
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