1.目标:用户登录后,再次登录无需输入用户名和密码
2.思路:将用户的信息保存为cookie
每次用户访问网站,通过filter拦截所有请求,在filter中读取所有的cookie,如果找到了保存登录信息的cookie,那么在cookie中读取登录信息,然后直接跳过登录页面,如果没有找到,那么切换到登录页面
3.具体代码
3.1登录界面
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c"%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html">
</head>
<body>
<p>主页
<p>
<c:choose>
<c:when test="${empty sessionScope.name}">
<form name="x" action="<c:url value='/LoginServlet' />"
method="post">
name:<input type="text" name="name" />
auto:
<input type="radio"name="auto" value="-1" checked="checked">不自动登陆
<input type="radio" name="auto" value="1">1天
<input type="radio" name="auto" value="7">7天 <input type="submit" value="提交">
</form>
</c:when>
<c:otherwise>
欢迎你:${name }<br>
<a href="<c:url value='/LoginServlet'/>">退出</a>
</c:otherwise>
</c:choose>
</body>
</html>
3.2filter过滤器
package s051301;
import java.io.IOException;
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;
public class Filter implements javax.servlet.Filter{
private String encoding;
public void init(FilterConfig con) throws ServletException {
}
public void doFilter(ServletRequest req, ServletResponse res,
FilterChain chain) throws IOException, ServletException {
System.err.println("dofilter service()");
req.setCharacterEncoding("UTF-8");
res.setContentType("text/html;charset=" + "UTF-8");
HttpServletRequest request=(HttpServletRequest)req;
Cookie[] cs=request.getCookies();
if(cs!=null)
{
for(Cookie c:cs)
{
if(c.getName().equals("log")); //cookie怎么存的就怎么取
{
String value=c.getValue(); //存放cookie中的值,就是用户的名称
request.getSession().setAttribute("name", value);
break;
}
}
}
chain.doFilter(req, res);
}
public void destroy() {
}
}
3.3Servlet
package s051301;
import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.http.Cookie;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
public class LoginServlet extends HttpServlet {
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
this.doPost(request, response);
}
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
request.setCharacterEncoding("UTF-8");
response.setContentType("text/html;charset=UTF-8");
String name=request.getParameter("name");
String auto=request.getParameter("auto");
System.err.println(name);
System.err.println(auto);
if(!auto.equals("-1"))
{
request.getSession().setAttribute("name", name);
int day=Integer.parseInt(auto);
int seconds=60*60*24*day;
//声明cookie
Cookie c=new Cookie("log",name);
c.setMaxAge(seconds);
c.setPath(request.getContextPath());
response.addCookie(c);
}
//重定向到主页
response.sendRedirect(request.getContextPath()+"/index.jsp");
}
}
3.4web.xml配置
<?xml version="1.0" encoding="UTF-8"?> <web-app version="3.0" xmlns="http://java.sun.com/xml/ns/javaee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd"> <filter> <filter-name>filter</filter-name> <filter-class>s051301.Filter</filter-class> </filter> <filter-mapping> <filter-name>filter</filter-name> <url-pattern>/*</url-pattern> </filter-mapping> <servlet> <servlet-name>LoginServlet</servlet-name> <servlet-class>s051301.LoginServlet</servlet-class> </servlet> <servlet-mapping> <servlet-name>LoginServlet</servlet-name> <url-pattern>/LoginServlet</url-pattern> </servlet-mapping> </web-app>