Jsp+Servlet+Cookie实现记住密码，自动登录，防止表单提交，记录登录次数

package com.xh.web; import java.io.IOException; import java.net.URLEncoder; import java.sql.Connection; import java.sql.PreparedStatement; import java.sql.ResultSet; import java.sql.SQLException; import javax.servlet.ServletException; import javax.servlet.annotation.WebServlet; 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 com.xh.util.DBUtil; /** *检查用户名和密码是否正确 */ @WebServlet(name="LoginCheck",urlPatterns="/check") public class LoginCheck extends HttpServlet { @Override protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { req.setCharacterEncoding("utf-8"); //获取表单数据 String user=req.getParameter("user").trim(); String password=req.getParameter("password").trim(); //把用户名保持在session里面，以实现会话跟踪 HttpSession session=req.getSession(); session.setAttribute("user",user); //如果用户名密码正确 if(check(user, password)){ //获取记住密码的值 复选框会传递一个(on/off) String remember=req.getParameter("remember"); //把用户名和密码加起来 String value=user+"&"+password; //用Cookie保存记住密码和自动登录 Cookie save=new Cookie("remember_pwd",URLEncoder.encode(value, "UTF-8"));//编码 Cookie auto_login=new Cookie("auto_login","auto"); //如果选择记住密码,则把用户名密码保存在cookie中 if("on".equals(remember)){ save.setMaxAge(Integer.MAX_VALUE); }else{ //不选择，就不保存。关闭浏览器cookie就失效 save.setMaxAge(0); } //自动登录的值，复选框会传递一个(on/off) String autoLogin=req.getParameter("auto_login"); if("on".equals(autoLogin)){ save.setMaxAge(Integer.MAX_VALUE); auto_login.setMaxAge(Integer.MAX_VALUE); }else{ auto_login.setMaxAge(0); } //保存用户名和密码 resp.addCookie(save); //自动登录 resp.addCookie(auto_login); // encodeRedirectURL()方法首先判断session是否失效或者用户没有禁用cookies，如果是直接返回url。如果禁用了cookie则采用url重写方式进行会话跟踪 resp.sendRedirect(resp.encodeRedirectURL("success.jsp")); }else{ //用户名和密码错误 req.setAttribute("loginIsError","fail"); //转发 this.getServletContext().getRequestDispatcher(resp.encodeRedirectURL("/login.jsp")).forward(req, resp); //req.getRequestDispatcher("login.jsp").forward(req, resp); } } //通过查询数据库，判断输入的用户名和密码是否正确 private boolean check(String username,String password){ Connection con=null; PreparedStatement ps=null; ResultSet rs=null; try { con=DBUtil.getConnection(); String sql="select * from user"; ps=con.prepareStatement(sql); rs=ps.executeQuery(); while(rs.next()){ if(rs.getString("username").equals(username) && rs.getString("password").equals(password)){ return true; } } rs.close(); } catch (Exception e) { e.printStackTrace(); }finally{ if(null!=ps){ try { ps.close(); } catch (SQLException e) { e.printStackTrace(); } } DBUtil.close(con); } return false; } }