验证码的实现

验证码的实现需要用到session技术，就先说说session是干什么的吧

Session技术是将数据存储在服务器端的技术，会为每个客户端都创建一块内存空间存储客户的数据，但客户端需要每次都携带一个标识ID去服务器中寻找属于自己的内存空间。所以说Session的实现是基于Cookie，Session需要借助于Cookie存储客户的唯一性标识JSESSIONID （Cookie技术是将用户的数据存储到客户端的技术）

Session技术：存到服务器端借助cookie存储JSESSIONID

HttpSession session = request.getSession();

session.setAttribute(name,value); //将值value 他的名字是name 存储到session中

session.getAttribute(name); //获取name（上边的名为name的东西）

session生命周期

创建：第一次指定request.getSession();

销毁：服务器关闭、session失效/过期、手动session.invalidate();

session作用范围：默认一会话中

下面开始验证码的实现

首先需要一个jar包 itcast-tools-1.4.2.jar

需要的在这里领就行

链接: https://pan.baidu.com/s/1zE74X9sGCmw14sSdbuWTig 提取码: zew5 复制这段内容后打开百度网盘手机App，操作更方便哦

先是jsp页面

 1 <%@ page language="java" contentType="text/html; charset=UTF-8"
 2     pageEncoding="UTF-8" import="java.util.*"%>
 3 <%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
 4 <!DOCTYPE html>
 5 <html>
 6 <head>
 7 <meta charset="UTF-8">
 8 <title>Insert title here</title>
 9 <meta http-equiv="pragma" content="no-cache">
10 <meta http-equiv="cache-control" content="no-cache">
11 <meta http-equiv="expires" content="0">
12 <meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
13 <meta http-equiv="description" content="This is my page">
14 <script type="text/javascript">
15 　　function _hyz() {
16     　　/*
17     　　1. 获取<img>元素
18     　　2. 给它的src指向为/tools/VerifyCodeServlet
19     　　*/
20     　　var img = document.getElementById("imgVerifyCode");
21     　　// 需要给出一个参数，这个参数每次都不同，这样才能干掉浏览器缓存！
22     　　img.src = "/TestDenglu/VerifyCodeServlet?a=" + new Date().getTime();
23 　　}
24 　　</script>
25 </head>
26 <body>
27     <%--
28 　　1. 写表单，其中包含图片（验证码）
29 　　2. 让图片显示出来：
30 　　把<img>的src指向VerifyCodeServlet，你需要在web.xml中部署VerfiyCodeServlet
31 　　3. 换一张
32 　　--%>
33     <div style="color: red"><%=request.getAttribute("loginInfo")==null?"":request.getAttribute("loginInfo") %></div>
34     <form action="/TestDenglu/LoginServlet?method=checkCode" method="post">
35         
36         <input type="hidden" name="method" value="login"> 
37         用户名：<input type="text" name="username" /><br /> 
38         密 码：<input type="password" name="password" /><br /> 
39         验证码：<input type="text" name="verifyCode" /><br />
40             <img src="/TestDenglu/VerifyCodeServlet" id="imgVerifyCode" /> <a
41             href="javascript:_hyz()">换一张</a> <br /> 
42         <input type="submit" value="提交" />
43     </form>

（其中的TestDenglu是我的项目名）

web.xml部署

<servlet>
    <servlet-name>VerifyCodeServlet</servlet-name>
    <servlet-class>cn.itcast.vcode.servlet.VerifyCodeServlet</servlet-class>
  </servlet>
  
  <servlet-mapping>
      <servlet-name>VerifyCodeServlet</servlet-name>
      <url-pattern>/VerifyCodeServlet</url-pattern>
  </servlet-mapping>

LoginServlet

  1 package com.jdbc.servlet;
  2 
  3 import java.io.IOException;
  4 import java.io.PrintWriter;
  5 
  6 import javax.servlet.ServletException;
  7 import javax.servlet.annotation.WebServlet;
  8 import javax.servlet.http.HttpServlet;
  9 import javax.servlet.http.HttpServletRequest;
 10 import javax.servlet.http.HttpServletResponse;
 11 
 12 import com.jdbc.dao.UserDao;
 13 
 14 /**
 15  * Servlet implementation class LoginServlet
 16  */
 17 @WebServlet("/LoginServlet")
 18 public class LoginServlet extends HttpServlet {
 19     private static final long serialVersionUID = 1L;
 20 
 21     /**
 22      * @see HttpServlet#HttpServlet()
 23      */
 24     public LoginServlet() {
 25         super();
 26         // TODO Auto-generated constructor stub
 27     }
 28 
 29     /**
 30      * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse
 31      *      response)
 32      */
 33     protected void doGet(HttpServletRequest request, HttpServletResponse response)
 34             throws ServletException, IOException {
 35         // TODO Auto-generated method stub
 36         response.setContentType("text/html;charset=UTF-8");
 37         request.setCharacterEncoding("UTF-8");
 38         
 39         String method = request.getParameter("method");
 40         if(method.equals("checkCode"))
 41         {
 42             checkCode(request,response);
 43         }
 44         
 45     }
 46     
 47     public void checkCode(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException{
 48         request.setCharacterEncoding("UTF-8");
 49         
 50         String checkCode_client = request.getParameter("verifyCode");
 51             // VerifyCodeServlet会把真正的验证码保存到session中
 52         String checkCode_session = (String) request.getSession().getAttribute("vCode");
 53             
 54         if(!checkCode_session.equals(checkCode_client)) {
 55             request.setAttribute("loginInfo", "您输入的验证码不正确");
 56             request.getRequestDispatcher("/form.jsp").forward(request, response);
 57             return;
 58         }
 59         if(checkCode_session.equals(checkCode_client)) {
 60             request.setCharacterEncoding("utf-8");
 61             response.setContentType("text/html;charset=utf-8");
 62             String username = request.getParameter("username");
 63             String password = request.getParameter("password");
 64             String psw =new UserDao().findUsername(username);
 65             
 66             //request.getSession().setAttribute("loginInfo", username);
 67            
 68             if(psw ==null){
 69                 PrintWriter out = response.getWriter();
 70                 out.println(" <script type='text/javascript'> alert('该用户不存在');window.location.href='login.jsp'</script>");    
 71                 out.println("</HTML>");
 72                 out.flush();
 73                 out.close();       
 74             }
 75             if(psw!=null&&!psw.equals(password)){
 76                 PrintWriter out = response.getWriter();
 77                 out.println(" <script type='text/javascript'> alert('密码错误，请重新录入');window.location.href='login.jsp'</script>");    
 78                 out.println("</HTML>");
 79                 out.flush();
 80                 out.close();   
 81             }
 82             if(psw!=null&&psw.equals(password)){
 83                 PrintWriter out = response.getWriter();
 84                 out.println(" <script type='text/javascript'> alert('登陆成功！');window.location.href='welcome.jsp'</script>");      
 85                 out.println("</HTML>");
 86                 out.flush();
 87                 out.close();
 88                 out.print(true);
 89             }
 90         }
 91         
 92     }
 93 
 94     
 95 
 96     /**
 97      * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse
 98      *      response)
 99      */
100     protected void doPost(HttpServletRequest request, HttpServletResponse response)
101             throws ServletException, IOException {
102         // TODO Auto-generated method stub
103         doGet(request, response);
104     }
105 
106 }

posted @ 2020-03-01 09:57 谜语+ 阅读(285) 评论(0) 编辑收藏举报

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验证码的实现

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