参考：http://blog.csdn.net/u014010769/article/details/46792919#comments
自动登录分析:
如果是第一次登陆就把user放到session域中，同时建立一个cookie把用户名和密码保存到cookie中，然后写一个过滤器，
如果是未登录的状态就把cookie中把用户名和密码拿出来和数据库中查询的作比较，如果一致就把user设置到session域中。
1.登陆页面login.jsp
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%> <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"> <html> <head> <title></title> <meta http-equiv=" pragma" content="no-cache"> <meta http-equiv="cache-control" content="no-cache"> <meta http-equiv="expires" content="0"> </head> <body> <h1>登录页面</h1><hr> <form action="${pageContext.request.contextPath }/servlet/LoginServlet" method="post"> 用户名：<input type="text" name="name"/><br> 密码：<input type="password" name="password"/><br> <input type="checkbox" name="autologin" value="true"/>30天内自动登录<br> <input type="submit" value="提交"/> </form> </body> </html> 2.loginServlet如果登陆成功就添加cookie package cn.itheima.web; import java.io.IOException ; import java.sql.SQLException; import java.util.HashMap; import javax.servlet.ServletContext; import javax.servlet.ServletException; import javax.servlet.http.Cookie; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import javax.servlet.http.HttpSession; import org.apache.commons.dbutils.QueryRunner; import org.apache.commons.dbutils.handlers.BeanHandler; import cn.itheima.domain.User; import com.itheima.util.DataSourceUtil; public class LoginServlet extends HttpServlet { public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { request.setCharacterEncoding("utf-8"); response.setContentType("text/html;charset=utf-8"); //1.获取请求参数 String name = request.getParameter("name"); String password = request.getParameter("password"); //2.验证密码和数据库中的是否一致 User user=null; try { QueryRunner runner=new QueryRunner(DataSourceUtil.getSource()); String sql="select * from user where name=? and password=?"; user=runner.query(sql, new BeanHandler<User>(User.class),name,password); } catch (SQLException e) { e.printStackTrace(); throw new RuntimeException(); } //3.检验 if(user==null){ response.getWriter().write("用户名不存在！"); }else{ request.getSession().setAttribute("user", user); if("true".equals(request.getParameter("autologin"))){ Cookie c=new Cookie("autologin", user.getName()+":"+user.getPassword()); c.setMaxAge(60*60*12*30); c.setPath(request.getContextPath()); response.addCookie(c); } response.sendRedirect(request.getContextPath()+"/index.jsp"); } } public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { doGet(request, response); } } 3.一个过滤器：完成了自动登录功能 package cn.itheima.filter; import java.io.IOException; import java.sql.SQLException; 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 org.apache.commons.dbutils.QueryRunner; import org.apache.commons.dbutils.handlers.BeanHandler; import cn.itheima.domain.User; import com.itheima.util.DataSourceUtil; public class AutoLoginFilter implements Filter{ public void init(FilterConfig filterConfig) throws ServletException { } public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException { HttpServletRequest req=(HttpServletRequest) request; HttpServletResponse res=(HttpServletResponse) response; Cookie findC=null; //1.只有未登录的用户才可以自动登录 if(req.getSession().getAttribute("user")==null||req.getSession(false)==null){ //1.获取cookies遍历所有的cookie Cookie[] cs = req.getCookies(); if(cs!=null){ for(Cookie c:cs){ if(c.getName().equals("autologin")){ findC=c; break;//找到了就跳出循环 } } } if(findC!=null){ //判断cookie中的用户名和密码跟数据库的是否一致 String cName = findC.getValue(); String[] values = cName.split(":"); String name=values[0]; String password=values[1]; //2.验证密码和数据库中的是否一致 User user=null; try { QueryRunner runner=new QueryRunner(DataSourceUtil.getSource()); String sql="select * from user where name=? and password=?"; user=runner.query(sql, new BeanHandler<User>(User.class),name,password); } catch (SQLException e) { e.printStackTrace(); throw new RuntimeException(); } req.getSession().setAttribute("user", user); } } chain.doFilter(req, res); } public void destroy() { } } 4.注销功能：不仅要杀死session还要把cookie清除否则注销不成功。package cn.itheima.web; 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 LogoutServlet extends HttpServlet { public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { if(request.getSession(false)!=null){ request.getSession().invalidate(); } //删除cookie Cookie c=new Cookie("autologin",""); c.setMaxAge(0); c.setPath(request.getContextPath()); response.addCookie(c); //重定向到主页 response.sendRedirect(request.getContextPath()+"/index.jsp"); } public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { doGet(request, response); } }
