在jsp中用bean和servlet联合实现用户注册、登录

在jsp中用bean和servlet联合实现用户注册、登录(9) 2、本例主要研究注册的过程，其中的Email检测等方法并不完善，若要应用请自行设计方法

四、编写用户登陆的Servlet：login.java

//login.java

//import required classes
import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;
import java.sql.*;

//class login
public class login extends HttpServlet
{
 public void doGet(HttpServletRequest req,HttpServletResponse res)
 throws IOException,ServletException
 {
  String username = req.getParameter("username");
  String password = req.getParameter("password");
  if(this.checklogin(username,password))
  {
   Cookie mylogin = new Cookie("username",username);
   mylogin.setVersion(1);
   mylogin.setPath("/");
   mylogin.setComment("Your login username");
   res.addCookie(mylogin);
  }
  //Cookie[] myCookies = req.getCookies();
  //String nameValue = this.getCookieValue(myCookies,"username","not found");
  //PrintWriter out = res.getWriter();
  //out.println("username" + ":" + nameValue);
  //out.println("Test Cookie SUCcess!");
  res.sendRedirect("/index.jsp");
 }
 
 public void doPost(HttpServletRequest req,HttpServletResponse res)
 throws IOException,ServletException
 {
  doGet(req,res);
 }
 
 public static String getCookieValue(Cookie[] cookies,String cookieName,String defaultValue)
 {
  for(int i=0;i<cookies.length;i++) {
  Cookie cookie = cookies[i];
  if (cookieName.equals(cookie.getName()))
  return(cookie.getValue());
 }
  return(defaultValue);
 }

 
 public boolean checklogin(String username,String password)
 {
  try{
   DBConn loginConn = new DBConn();