使用重寫url機制實現驗證碼換一張功能

2019-11-19 15:56:09

字體：大中小

來源：轉載

供稿：網友

重寫URL機制：為了保證一個url的地址唯一，可每次向服務器傳遞的參數不一樣即可。

由數據請求的抱頭信息可分析到：抱頭信息包括http協議，IP地址，端口號，工程名，請求參數列表，要想訪問的資源不發生變化，只能變化參數連表。

此處在實現驗證碼的換一張的功能時，就是利用了改變參數列表的值進行刷新。

詳細代碼實現：

<%@page import="javax.imageio.ImageIO"%> <%@page import="java.awt.Font"%> <%@page import="java.awt.Color"%> <%@page import="java.awt.Graphics"%> <%@page import="java.awt.image.BufferedImage"%> <%@ page contentType="image/jpeg" language="java" import="java.util.*" pageEncoding="UTF-8"%> <% int w=100; int h=30; BufferedImage bi=new BufferedImage(w,h,BufferedImage.TYPE_INT_RGB); Graphics g=bi.getGraphics(); Color c=g.getColor(); Font f=g.getFont();  Random r=new Random(); Color bg=new Color(150+r.nextInt(100),150+r.nextInt(100),150+r.nextInt(100)); g.setColor(bg); g.fillRect(0, 0, w, h); String code=""; for(int i=1;i<=4;i++){ int num=r.nextInt(10); code=code+num; Color num_c=new Color(r.nextInt(150),r.nextInt(150),r.nextInt(150)); g.setColor(num_c); g.drawString(String.valueOf(num), 20*i, h/2); } request.getSession().setAttribute("code", code); //清空緩存 response.setHeader("pragma", "bo-cache"); response.setHeader("cache-control", "bo-cache"); response.addDateHeader("expires", 0); ImageIO.write(bi, "jpeg", response.getOutputStream()); out.close();  %>

添加登錄頁面：

<%@ page contentType="text/html; charset=utf-8" language="java" import="java.util.*" pageEncoding="UTF-8"%> <%String path = request.getContextPath(); String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/"; %> <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"> <html>  <head>   <base href="<%=basePath%>" rel="external nofollow" >   <title>My JSP 'login.jsp' starting page</title>   <meta http-equiv="pragma" content="no-cache">   <meta http-equiv="cache-control" content="no-cache">   <meta http-equiv="expires" content="0">     <meta http-equiv="keywords" content="keyword1,keyword2,keyword3">   <meta http-equiv="description" content="This is my page">   <!--   <link rel="stylesheet" type="text/css" href="styles.css" rel="external nofollow" >   -->   <script type="text/javascript"> function changeimage(){ var d=new Date();//生成時間戳， document.getElementById("img").src="image.jsp?t="+d;//由變化的時間使參數連表發生變化，url重寫 } </script>  </head>  <body>  <font color="red">${requestScope.msg }</font>   <form action="loginServlet" method="post">   name:<input type="text" name="uname"><br>   pwd:<input type="pwd" name="upwd"><br>   code:<input type="text" name="code" size="5"><img id="img" alt="" src="image.jsp "><a onclick="changeimage()">換一張</a><br>   <input type="submit" >   </form>  </body> </html>

利用時間的變化，每次生成時間戳，傳參給請求的url，達到重寫url的目的，從而實現了換一張的刷新功能。