产生验证码图片的文件image.jsp <%...@ page contentType="image/jpeg" import="java.awt.*,java.awt.image.*,java.util.*,javax.imageio.*" %><%...!Color getRandColor(int fc,int bc){//给定范围获得随机颜色 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); }%><%...//设置页面不缓存response.setHeader("Pragma","No-cache");response.setHeader("Cache-Control","no-cache");response.setDateHeader("Expires", 0);// 在内存中创建图象int width=60, height=20;BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);// 获取图形上下文Graphics g = image.getGraphics();//生成随机类Random random = new Random();// 设定背景色g.setColor(getRandColor(200,250));g.fillRect(0, 0, width, height);//设定字体g.setFont(new Font("Times New Roman",Font.PLAIN,18));//画边框//g.setColor(new Color());//g.drawRect(0,0,width-1,height-1);// 随机产生155条干扰线,使图象中的认证码不易被其它程序探测到g.setColor(getRandColor(160,200));for (int i=0;i<155;i++){ int x = random.nextInt(width); int y = random.nextInt(height); int xl = random.nextInt(12); int yl = random.nextInt(12); g.drawLine(x,y,x+xl,y+yl);}// 取随机产生的认证码(4位数字)String sRand="";for (int i=0;i<4;i++){ String rand=String.valueOf(random.nextInt(10)); sRand+=rand; // 将认证码显示到图象中 g.setColor(new Color(20+random.nextInt(110),20+random.nextInt(110),20+random.nextInt(110)));//调用函数出来的颜色相同,可能是因为种子太接近,所以只能直接生成 g.drawString(rand,13*i+6,16);}// 将认证码存入SESSIONsession.setAttribute("rand",sRand);// 图象生效g.dispose();// 输出图象到页面ImageIO.write(image, "JPEG", response.getOutputStream());%> 使用验证码图片的文件a.jsp <%...@ page contentType="text/html;charset=gb2312" %><!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"><html><head><title>认证码输入页面</title><meta http-equiv="Content-Type" content="text/html; charset=gb2312"><META HTTP-EQUIV="Pragma" CONTENT="no-cache"> <META HTTP-EQUIV="Cache-Control" CONTENT="no-cache"> <META HTTP-EQUIV="Expires" CONTENT="0"> </head><body><form method=post action="check.jsp"><table> <tr> <td align=left>系统产生的认证码:</td> <td> <img border=0 p"></td></tr> <tr> <td align=left>输入上面的认证码:</td> <td> <input type=text maxlength=4 value=""></td></tr> <tr> <td colspan=2 align=center> <input type=submit value="提交检测"></td></tr></form></body></html> 验证的页面check.jsp <%...@ page contentType="text/html; charset=gb2312" language="java" import="java.sql.*" errorPage="" %><html><head><title>认证码验证页面</title><meta http-equiv="Content-Type" content="text/html; charset=gb2312"><META HTTP-EQUIV="Pragma" CONTENT="no-cache"> <META HTTP-EQUIV="Cache-Control" CONTENT="no-cache"> <META HTTP-EQUIV="Expires" CONTENT="0"> </head><body><%... String rand = (String)session.getAttribute("rand"); String input = request.getParameter("rand");%> 系统产生的认证码为: <%= rand %<br> 您输入的认证码为: <%= input %><br><br><%... if (rand.equals(input)) {%><font color=green>输入相同,认证成功!</font><%... } else {%><font color=red>输入不同,认证失败!</font><%... }%></body></html>