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登录时常常要用到验证码验证,下面是一个简单的纯数字验证码,详细代码见image.jsp,将每次生成的验证码文本直接存入session中,登录时方便后台从session中取值验证:
<%@ page contentType="image/jpeg" import="java.awt.*, java.awt.image.*,java.util.*,javax.imageio.*" pageEncoding="utf-8"%> <%!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); }%> <% out.clear();//这句针对resin服务器,如果是tomacat可以不要这句 response.setHeader("Pragma", "No-cache"); response.setHeader("Cache-Control", "no-cache"); response.setDateHeader("Expires", 0); int width = 60, height = 20; BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB); Graphics g = image.getGraphics(); Random random = new Random(); g.setColor(getRandColor(200, 250)); g.fillRect(0, 0, width, height); g.setFont(new Font("Times New Roman", Font.PLAIN, 18)); 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); } String sRand = ""; for (int i = 0; i < 4; i++) { String rand = String.valueOf(random.nextInt(10)); sRand += rand; g.setColor(new Color(20 + random.nextInt(110), 20 + random .nextInt(110), 20 + random.nextInt(110))); g.drawString(rand, 13 * i + 6, 16); } // 将认证码存入SESSION session.setAttribute("sRand", sRand); g.dispose(); ImageIO.write(image, "JPEG", response.getOutputStream()); %>
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原文地址:http://www.cnblogs.com/caiya928/p/4852084.html