验证码（摘）

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2024-09-29 19:23:02 219人阅读

1、前台的代码

<%@ 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>My JSP ‘pic-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">    
    <script type="text/javascript" src="js/jquery-1.8.3.min.js"></script>
    <script type="text/javascript">  
    function reload(){  
        document.getElementById("image").src="<%=request.getContextPath() %>/ImageServlet?date="+new Date().getTime();  
        $("#checkcode").val("");   // 将验证码清空  
    }   
       
     function verificationcode(){  
         var text=$.trim($("#checkcode").val());  
         $.post("${pageContext.request.contextPath}/VerificationServlet",{op:text},function(data){  
             data=parseInt($.trim(data));  
             if(data>0){  
                 $("#span").text("验证成功!").css("color","green");  
             }else{  
                $("#span").text("验证失败!").css("color","red");  
                reload();  //验证失败后需要更换验证码  
                 $("#checkcode").val(""); // 将验证码清空  
             }  
        });  
        
     }  
</script> 
    
  </head>
  
  <body>
          
         验证码：<input type="text" name="checkcode"  id="checkcode" onchange="javascript:verificationcode()"/>  
             <img src="<%=request.getContextPath() %>/ImageServlet" title="点击换一张" id="image"  onclick="javascript:reload()"/>  <span id="span"></span>  
                
             
  </body>
</html>

2、这里图片的src是一个servlet-ImageServlet.java

package com.java.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.imageio.ImageIO;
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 javax.servlet.http.HttpSession;


@WebServlet("/ImageServlet")
public class ImageServlet extends HttpServlet {
    private static final long serialVersionUID = 1L;
   
    public ImageServlet() {
        super();
       
    }

    
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
                
                request.setCharacterEncoding("utf-8");  
                 
                //在内存中创建图象  
                 int width = 80;  
                 int height = 25;
                 BufferedImage bfi = new BufferedImage(width,height,BufferedImage.TYPE_INT_RGB);  
                 //创建图象
                 Graphics g = bfi.getGraphics(); 
                
                 g.fillRect(0, 0, width, height);  
           
                 //验证码字符范围  
                 char[] ch = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789".toCharArray();  
                 Random r = new Random();   
                 int index;    
                 StringBuffer sb = new StringBuffer(); //保存字符串  
                 //随机产生认证码
                 for(int i=0; i<4; i++){  
                     index = r.nextInt(ch.length);  
                     g.setColor(new Color(r.nextInt(255),r.nextInt(255),r.nextInt(255)));  
                     Font font = new Font("Tines Nev Roman", 30, 20);  
                     g.setFont(font);  
                     g.drawString(ch[index]+"", (i*20)+2, 23);  
                     sb.append(ch[index]);  
                }  
                   
                 // 添加噪点  
                int area = (int) (0.02 * width * height);  
                 for(int i=0; i<area; ++i){  
                     int x = (int)(Math.random() * width);  
                    int y = (int)(Math.random() * height);  
                     bfi.setRGB(x, y, (int)(Math.random() * 255));  
                 }  
                   
               //设置验证码中的干扰线  
                 for (int i = 0; i < 1; i++) {    
                       //随机获取干扰线的起点和终点  
                       int xstart = (int)(Math.random() * width);  
                       int ystart = (int)(Math.random() * height);  
                       int xend = (int)(Math.random() * width);  
                       int yend = (int)(Math.random() * height);  
                       g.setColor(interLine(1, 255));  
                       g.drawLine(xstart, ystart, xend, yend);  
                     }  
                 HttpSession session = request.getSession();  //保存到session  
                 session.setAttribute("verificationCode", sb.toString());  
                 ImageIO.write(bfi, "JPG", response.getOutputStream());  //写到输出流  

    }
    private static Color interLine(int Low, int High){  
                if(Low > 255)  
                    Low = 255;  
                if(High > 255)  
                    High = 255;  
                if(Low < 0)  
                    Low = 0;  
                if(High < 0)  
                    High = 0;  
                int interval = High - Low;  
                int r = Low + (int)(Math.random() * interval);  
                int g = Low + (int)(Math.random() * interval);  
                int b = Low + (int)(Math.random() * interval);  
                return new Color(r, g, b);  
    }  

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

}

这里使用ImageServlet生成图片验证码，使用post后台验证，在点击标签换验证码图片的时候，一定要在调用生成图片前加一个时间戳，也就是上面的document.getElementById("image").src="http://www.mamicode.com//imageServlet?date="+new Date().getTime();这句代码的最后加？后面的代码一定不能少，因为浏览器是由缓存的，如果不加时间戳，在点击标签换图片时，验证码图片不会正常更换。

为了便于比对结果，一定要将字符串保存到session。因为session是当前会话有效的，也就是说在你关闭浏览器之前，session里的值都是可以取到的。这里为了增加验证的难度，是不区分大小写的。噪点和干扰线的数量也是可调的。
3、最后是使用VerificationServlet对验证码图片上的字符与输入的字符串进行比对！把存入session中的verificationCode取出来与checkcode进行比对，返回结果

package com.java.servlet;

import java.io.IOException;
import java.io.PrintWriter;

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 javax.servlet.http.HttpSession;


@WebServlet("/VerificationServlet")
public class VerificationServlet extends HttpServlet {
    private static final long serialVersionUID = 1L;
       
    
    public VerificationServlet() {
        super();
        
    }

    
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        HttpSession session =request.getSession();  
        String verificationCode = (String)session.getAttribute("verificationCode");  
        String checkcode = request.getParameter("op");  
        PrintWriter out = response.getWriter();  
        if(checkcode.equals(verificationCode)){  
           out.println(1);  
        }else{  
            out.println(0);  
        }  

    }

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

}

4、效果

技术分享

摘自：http://blog.csdn.net/weixian52034/article/details/52186207

验证码（摘）

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验证码（摘）

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