首页新闻找找看学习计划

Servlet 被访问次数

0
[待解决问题]

简单的登录页面  一次请求为什么servlet执行了两次

package com.neusoft.web;

import java.io.IOException;
import java.util.Map;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import com.neusoft.services.impl.LoginServices;

/**
 * Servlet implementation class LoginServlet
 */
@WebServlet("/login.html")
public class LoginServlet extends HttpServlet 
{
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException 
    {
       String path="/login.jsp";
       try
       {
               //1.获取页面数据
               String uname=request.getParameter("uname");
               String pwd=request.getParameter("pwd");
               //2.实例化Services
               LoginServices services=new LoginServices();
               //3.获取用户信息
               Map<String,String> userinfo=services.checkUser(uname, pwd);
               System.out.println("********************************");
               if(userinfo!=null)
               {
                   //System.out.println(userinfo);
                   //将用户数据存入session
                   request.getSession().setAttribute("USERINFO", userinfo);
                   //跳转到系统主页
                   path="/Main.jsp";
               }
               else
               {
                   request.setAttribute("msg", "用户名或密码错误!");
               }    
       }    
       catch(Exception ex)
       {
           ex.printStackTrace();
       }
       request.getRequestDispatcher(path).forward(request, response);
    }

    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException 
    {
        this.doGet(request, response);
    }

}

jsp代码

<%@ page language="java" pageEncoding="GBK"%>
<html>
<head>
<title>Insert title here</title>
<style type="text/css">
body {background-color: gray}
</style>
</head>
<body>
<pre>











</pre>
<form action="<%=request.getContextPath()%>/login.html" method="post">
<table border="1" width="45%" align="center">
  <tr>
    <td colspan="100">
      &nbsp;${msg }
    </td>
  </tr>
  <tr>
    <td>登录名:</td>
    <td>
      <input type="text" name="uname" required="required" autofocus="autofocus">
    </td>
  </tr>
  <tr>
    <td>密码:</td>
    <td>
      <input type="password" name="pwd" required="required">
    </td>
  </tr>
  <tr>
    <td colspan="100" align="center">
      <input type="submit" name="next" value="登录">
    </td>
  </tr>
</table>
</form>
</body>
</html>

代码运行可能用到 

LoginServices里的
checkUser方法 ,就是验证账号密码的,
第一次进入是可以获取页面的账号密码pwd与uname是有值的,进行一次验证,然后他会再次调用访问一次,这是pwd
uname是null,而获取不到账号密码,然后
密码调用md5加密方法的时候就会空指针异常。
求大佬解惑
出问题的jsp。
<%@ page language="java" pageEncoding="GBK"%>
<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c" %>
<%String path=request.getContextPath();%>
<html>
<head>
<title>用户登录</title>
</head>
<body>
<pre>












</pre>
 <form action="<%=path%>/login" method="post">
<table border="1" align="center" width="30%">
 <tr>
 <td>账号:</td>
 <td>
 <input type="text" name="uacount" required="required">
 </td>
 </tr>
 <tr>
 <td>密码:</td>
 <td>
 <input type="password" name="upwd" required="required">
 </td>
 </tr>
 <tr>
  <td colspan="100" align="center">
    <input type="submit" name="next" value="登录">
  </td>
 </tr>
</table>
</form>
</body>
</html>
<%@ page language="java" pageEncoding="GBK"%>
<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c" %>
<%String path=request.getContextPath();%>
<html>
<head>
<title>用户登录</title>
</head>
<body>
<pre>












</pre>
 <form action="<%=path%>/login" method="post">
<table border="1" align="center" width="30%">
 <tr>
 <td>账号:</td>
 <td>
 <input type="text" name="uacount" required="required">
 </td>
 </tr>
 <tr>
 <td>密码:</td>
 <td>
 <input type="password" name="upwd" required="required">
 </td>
 </tr>
 <tr>
  <td colspan="100" align="center">
    <input type="submit" name="next" value="登录">
  </td>
 </tr>
</table>
</form>
</body>
</html>

 

 
窦光大大存大大凯的主页 窦光大大存大大凯 | 菜鸟二级 | 园豆:220
提问于:2017-11-08 19:44
< >
分享
所有回答(2)
1

页面get请求和post请求用的是一个servlet吧,应该分开吧。

Tony Lu | 园豆:32 (初学一级) | 2017-11-08 21:50

这个没影响吧 post提交在里边调用doget方法。

支持(0) 反对(0) 窦光大大存大大凯 | 园豆:220 (菜鸟二级) | 2017-11-09 11:35
0

三次握手啊

窦光大大存大大凯 | 园豆:220 (菜鸟二级) | 2018-08-22 11:26
清除回答草稿
   您需要登录以后才能回答,未注册用户请先注册