接着上一篇的前台jsp页面，我们单独写一个绘制验证码的jsp页面：

<%@ page contentType="image/jpeg"import="java.awt.*,java.awt.image.*,java.util.*,javax.imageio.*"pageEncoding="utf-8"%>
<%!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SESSION  session.setAttribute("numrand", sRand);// 图象生效  g.dispose();  // 输出图象到页面  ImageIO.write(image, "JPEG", response.getOutputStream());  out.clear();  out = pageContext.pushBody();   
%>