JSP动态生成验证码并单击切换验证码
jopen
11年前
验证码生成jsp代码：
<%@ page language="java" import="java.util.*" pageEncoding="gbk"%> <%@ 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 = 70, 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("宋体", Font.PLAIN, 18)); //画边框 g.setColor(Color.black); 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); } char[] cs = new char[] { '1', '2', '3', '4', '5', '6', '7', '8', '9', 'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'A', 'B', 'M' }; // 取随机产生的认证码(4位数字) String sRand = ""; for (int i = 0; i < 4; i++) { char c = cs[random.nextInt(cs.length)]; String rand = new Character(c).toString(); 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("rand", sRand); //这行代码使我们关注的重点 // 图象生效 g.dispose(); // 输出图象到页面 try { ImageIO.write(image, "JPEG", response.getOutputStream()); } catch (Exception e) { e.getMessage(); } finally { //解决以调用错误 out.clear(); out = pageContext.pushBody(); } %>测试页面： <body> 验证码：<img alt="" onclick="test();" src="image.jsp"> </body> <script type="text/javascript"> function test(){ var image = document.getElementsByTagName("img")[0]; var myDate = new Date(); image.src = "image.jsp?time="+myDate.getTime(); alert(image.src); } </script>测试效果： 