jsp 实现随即验证码

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<%@page import="java.awt.image.BufferedImage"%>
<%@page import="java.awt.Graphics2D"%>
<%@page import="java.awt.Color"%>
<%@page import="java.awt.Font"%>
<%@page import="javax.imageio.ImageIO"%>

<%
   int width = 60;
   int height = 20;
   // 创建具有可访问图像数据缓冲区的Image
   BufferedImage buffImg = new BufferedImage(width, height,
           BufferedImage.TYPE_INT_RGB);
   Graphics2D g = buffImg.createGraphics();

   // 创建一个随机数生成器
   Random random = new Random();

   g.setColor(Color.WHITE);
   g.fillRect(0, 0, width, height);

   // 创建字体，字体的大小应该根据图片的高度来定
   Font font = new Font("Times New Roman", Font.PLAIN, 18);
   // 设置字体
   g.setFont(font);

   // 画边框
   g.setColor(Color.BLACK);
   g.drawRect(0, 0, width - 1, height - 1);

   // 随机产生160条干扰线
   g.setColor(Color.LIGHT_GRAY);
   for (int i = 0; i < 160; i++) {
       int x = random.nextInt(width);
       int y = random.nextInt(height);
       int x1 = random.nextInt(12);
       int y1 = random.nextInt(12);
       g.drawLine(x, y, x + x1, y + y1);
   }

   // randomCode 用于保存随机产生的验证码
   StringBuffer randomCode = new StringBuffer();
   int red = 0, green = 0, blue = 0;

   // 随机产生4位数字的验证码
   for (int i = 0; i < 4; i++) {
       // 得到随机产生的验证码数字
       String strRand = String.valueOf(random.nextInt(10));

       // 产生随机的颜色分量来构造颜色值
       red = random.nextInt(110);
       green = random.nextInt(50);
       blue = random.nextInt(50);

       // 用随机产生的颜色将验证码绘制到图像中
       g.setColor(new Color(red, green, blue));
       g.drawString(strRand, 13 * i + 6, 16);

       randomCode.append(strRand);
   }

   // 将四位数字的验证码保存到session中
   //HttpSession session = request.getSession();
   session.setAttribute("randomCode", randomCode.toString());

   // 禁止图像缓存
   response.setHeader("Pragma", "no-cache");
   response.setHeader("Cache-Control", "no-cache");
   response.setDateHeader("Expires", 0);

   response.setContentType("image/jpeg");
   // 将图像输出到servlet输出流中
   ServletOutputStream sos = response.getOutputStream();
   ImageIO.write(buffImg, "jpeg", sos);
   sos.close();
   //sos = null;
   out.clear();
   out = pageContext.pushBody();
%>