前台生成验证码

 package cn.gov.csrc.servlet;  
   
 import java.awt.Color;  
 import java.awt.Font;  
 import java.awt.Graphics;  
 import java.awt.image.BufferedImage;  
 import java.io.IOException;  
 import java.util.Random;  
   
 import javax.servlet.ServletException;  
 import javax.servlet.http.HttpServlet;  
 import javax.servlet.http.HttpServletRequest;  
 import javax.servlet.http.HttpServletResponse;  
   
 import com.sun.image.codec.jpeg.JPEGCodec;  
 import com.sun.image.codec.jpeg.JPEGImageEncoder;  
   
 public class CodeServlet extends HttpServlet {  
   
     /** 
      * 产生验证码图片 
      */  
     public void doGet(HttpServletRequest request, HttpServletResponse response)  
             throws ServletException, IOException {  
         response.setContentType("image/jpeg");  
         response.setHeader("Cache-Control", "no-cache");  
         response.setHeader("Pragma", "No-cache");  
         response.setDateHeader("Expires", 0L);  
         int width = 80;  
         int height = 30;  
         BufferedImage image = new BufferedImage(width, height, 1);  
         Graphics g = image.getGraphics();  
         Random random = new Random();  
         g.setColor(getRandColor(200, 250));  
         g.fillRect(0, 0, width, height);  
         g.setFont(new Font("Arial", 0, 25));  
         g.setColor(getRandColor(160, 200));  
         for (int i = 0; i < 155; i++) {  
             int x = random.nextInt(width + 100);  
             int y = random.nextInt(height + 100);  
             int xl = random.nextInt(10);  
             int yl = random.nextInt(12);  
             g.drawOval(x, y, x + xl, y + yl);  
         }  
         String code = request.getParameter("code");  
         String sRand = code;  
         for (int i = 0; i < sRand.length(); i++) {  
             String rand = sRand.substring(i, i + 1);  
             g.setColor(new Color(20 + random.nextInt(110), 20 + random  
                     .nextInt(110), 20 + random.nextInt(110)));  
             g.drawString(rand, 14 * i + 5, 25);  
         }  
         g.dispose();  
         javax.servlet.ServletOutputStream imageOut = response.getOutputStream();  
         JPEGImageEncoder encoder = JPEGCodec.createJPEGEncoder(imageOut);  
         encoder.encode(image);  
     }  
   
     private Color getRandColor(int fc, int bc) {  
         Random random = new Random();  
         if (fc > 255)  
             fc = 255;  
         if (bc > 255)  
             bc = 255;  
         int r = fc + random.nextInt(bc - fc);  
         int g = fc + random.nextInt(bc - fc);  
         int b = fc + random.nextInt(bc - fc);  
         return new Color(r, g, b);  
     }  
   
 }  
 
    
  

2.Web.xml文件：

[html]view plain copy 
    
 
 <?xml version="1.0" encoding="UTF-8"?>  
 <web-app version="2.5" 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_2_5.xsd">  
     <display-name></display-name>  
     <welcome-file-list>  
         <welcome-file>index.jsp</welcome-file>  
     </welcome-file-list>  
     <servlet>  
         <servlet-name>CodeServlet</servlet-name>  
         <servlet-class>cn.gov.csrc.servlet.CodeServlet</servlet-class>  
     </servlet>  
     <servlet-mapping>  
         <servlet-name>CodeServlet</servlet-name>  
         <url-pattern>/CodeServlet</url-pattern>  
     </servlet-mapping>  
 </web-app>  

3.index.jsp：

[javascript]view plain copy 
    
 
 <%@ page 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%>">  
 <title>验证码测试</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">  
 <script language="javascript" type="text/javascript">  
 var code ; //在全局 定义验证码   
 function createCode(){    
     code = "";    
     var codeLength = 5;//验证码的长度    
     //所有候选组成验证码的字符，可以用中文    
     var selectChar = new Array(0,1,2,3,4,5,6,7,8,9,'A','B','C',  
             'D','E','F','G','H','I','J','K','L','M','N','O','P',  
             'Q','R','S','T','U','V','W','X','Y','Z','a','b','c',  
             'd','e','f','g','h','i','j','k','l','m','n','o','p',  
             'q','r','s','t','u','v','w','x','y','z');    
     for(var i=0;i<codeLength;i++){    
         var charIndex = Math.floor(Math.random()*60);    
         code +=selectChar[charIndex];    
     }    
     return code;    
 }    
 function validate (){    
     var inputCode = document.getElementById("vcode").value.toLowerCase();    
     if(inputCode.length <=0){    
         alert("请输入验证码！");    
         return false;    
     }    
     else if(inputCode != code.toLowerCase()){    
         alert("验证码输入错误！");    
         show();//刷新验证码    
         return false;    
     }else{    
         alert("^-^ OK");    
         return true;    
     }    
 }    
 function show(){    
         //显示验证码    
         document.getElementById("code").src="CodeServlet?code="+createCode();    
 }    
 window.onload = function() {  
         //document.onload=show();    
         show();//页面加载时加载验证码    
         //这时无论在ie还是在firefox中，js没有加载完，页面的东西是不会被执行的；    
     }    
 </script>  
 </head>  
   
 <body>  
     <form onsubmit="return validate();" action="" method="post">  
         <h3>jsp+js+servlet实现验证码</h3>  
         <br /> 用户名：<input type="text" name="" /><br /> 请输入验证码： <input  
             type="text" id="vcode" style="width: 60;" maxLength="5" /> <img  
             src="" id="code" /> <a href="#" mce_href="#"  
             onclick="javascript:show();return false;">看不清,换一张!</a><br /> <input  
             type="submit" />  
     </form>  
 </body>  
 </html>  

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