java中servlet实现登录验证的方法

LoginPro.java:
复制代码 代码如下:
package com.ncu;
import java.io.PrintWriter;

import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
public class LoginPro extends HttpServlet{
 public void doPost(HttpServletRequest req,HttpServletResponse res){
  try{
   String user=req.getParameter("userName");
   String pwd=req.getParameter("Pwd");
   if(user==null){
    user="";
   }
   if(pwd==null)
   {
    pwd="";
   }
   if(user.equals("nicolas")&&pwd.equals("nicolas")){
    //用户和密码合法
    //res.sendRedirect("wel");
//    res.setCharacterEncoding("gbk");
//    PrintWriter pw=res.getWriter();
//    pw.print("恭喜你，登录成功！！");
    res.sendRedirect("welcome");

   }
   else{
    //不合法进行跳转

    res.sendRedirect("login");//跳转到登录界面
   }

   
  }catch(Exception e)
  {
   e.printStackTrace();
  }
 }
}

Welcome.java:

复制代码 代码如下:
package com.ncu;
import java.io.PrintWriter;

import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
public class Welcome extends HttpServlet{
 public void doGet(HttpServletRequest req,HttpServletResponse res){
  try{
   res.setCharacterEncoding("gbk");
   PrintWriter pw=res.getWriter();
   pw.print("welcome，您好");

  }catch(Exception e)
  {
   e.printStackTrace();
  }
 }
}

web.xml
复制代码 代码如下:

 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">
   
 
    index.jsp
 
 
 
  hello
 
  com.ncu.Hello

 
  
  
     hello

 
  /nicolas
 
 
  helloservlet
  com.ncu.HelloServlet
 
 
  helloservlet
  /helloservlet
 
 
  helloHttpServlet
  com.ncu.helloHttpServlet
 
 
  helloHttpServlet
  /helloHttpServlet
 
 
  login
  com.ncu.login
 
 
  login
  /login
 
 
  loginpro
  com.ncu.LoginPro
 
 
  loginpro
  /loginpro
 
 
  welcome
  com.ncu.Welcome
 
 
  welcome
  /welcome