<c:choose>

  <c:when test="${empty sessionScope.name}">

    <form name="x" method="post" action="<c:url value='/LoginServlet'/>">

      Name:<input type="text" name="name"/><br/>

      auto:

      <input type="radio" name="auto" value="-1">不自动登录

      <br/>

      <input type="radio" name="auto" value="1">1天<br/>

      <input type="radio" name="auto" value="7">1周<br/>

      <input type="submit"/>

    </form>

  </c:when>

  <c:otherwise>

    你已经登录了:${name}<br/>

    <a href="<c:url value='/LoginServlet'/>">退出</a>

  </c:otherwise>

</c:choose>

public void doPost(HttpServletRequest request, HttpServletResponse response)

      throws ServletException, IOException {

    //接收用户姓名

    String name = request.getParameter("name");

    String auto = request.getParameter("auto");

    //将用户信息放到session

    request.getSession().setAttribute("name",name);

    //判断auto是否是-1

    if(!auto.equals("-1")){

      int day = Integer.parseInt(auto);//1|7

      int seconds = 60*60*24*day;

      //声明cookie

      Cookie c = new Cookie("autoLogin",name);

      c.setMaxAge(seconds);

      c.setPath(request.getContextPath());

      //保存cookie

      response.addCookie(c);

     

    }

  }

public void doFilter(ServletRequest request, ServletResponse response,

      FilterChain chain) throws IOException, ServletException {

    //在这儿读取cookie

    HttpServletRequest req = (HttpServletRequest) request;

    //获取所的有cookie

    Cookie[] cs = req.getCookies();

    if(cs!=null){

      for(Cookie c:cs){

       if(c.getName().equals("autoLogin")){//如果存在自动登录的cookie

         String value = c.getValue();//用户名称

         //登录成功是指

         req.getSession().setAttribute("name", value);

         break;

       }

      }

    }

    //不管是否自动登录成

    chain.doFilter(request, response);

  }

<filter>

  <filter-name>auto</filter-name>

  <filter-class>cn.itcast.filter.AutoFilter</filter-class>

 </filter>

 <filter-mapping>

  <filter-name>auto</filter-name>

  <url-pattern>/*</url-pattern>

 </filter-mapping>

System.err.println("用户退出");

    //删除整个session

    request.getSession().invalidate();

    Cookie c = new Cookie("autoLogin", "ddd");

    c.setMaxAge(0);

    c.setPath(request.getContextPath());

    response.addCookie(c);

//   request.getSession().removeAttribute("name");

    response.sendRedirect(request.getContextPath()+"/index.jsp");

package cn.hongxin.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.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

import javax.servlet.http.HttpSession;

 

public class LoginFilter implements Filter{

  public void init(FilterConfig filterConfig) throws ServletException {

  }

  public void doFilter(ServletRequest request, ServletResponse response,

      FilterChain chain) throws IOException, ServletException {

    //将request强转成htt...

    HttpServletRequest req = (HttpServletRequest) request;

    //获取session

    HttpSession ss = req.getSession();

    //从session中获取user

    if(ss.getAttribute("user")==null){

      System.err.println("你还没有登录");

      req.getSession().setAttribute("msg", "请你先登录");

      //重定向到登录

      HttpServletResponse resp = (HttpServletResponse) response;

      resp.sendRedirect(req.getContextPath()+"/index.jsp");[W2] 

    }else{

      //放行

      chain.doFilter(request, response);

    }

  }

  public void destroy() {

  }

}

<filter>

  <filter-name>login</filter-name>

  <filter-class>cn.itcast.filter.LoginFilter</filter-class>

 </filter>

 <filter-mapping>

  <filter-name>login</filter-name>

  <url-pattern>/jsps/*</url-pattern>

  <url-pattern>/views/*</url-pattern>

 </filter-mapping>