ImgServlet实现
...导入相关的包 public class ImgServlet extends HttpServlet { private 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); // System.out.println("r = " + r + ", g = " + g + ", b = " + b); return new Color(r, g, b); } public void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { resp.setContentType("image/jpeg"); resp.addHeader("pragma", "NO-cache"); resp.addHeader("Cache-Control", "no-cache"); resp.addDateHeader("Expries", 0); // 在内存中创建图象 int width = 50, 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, 255)); g.fillRect(0, 0, width, height); // 设定字体 g.setFont(new Font("华文彩云", Font.PLAIN, 20)); // 画边框 g.drawRect(0, 0, width - 1, height - 1); // 随机产生20条干扰线，使图象中的认证码不易被其它程序探测到 for (int i = 0; i < 40; i++) { g.setColor(getRandColor(50, 100)); int x = random.nextInt(width); int y = random.nextInt(height); int xl = random.nextInt(200)-100; int yl = random.nextInt(200)-100; 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 = "" + (char) (random.nextInt(26) + 97); 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, 11 * i + 2, 16); } // 将认证码存入SESSION // req.setAttribute("code", sRand); req.getSession().setAttribute("code", sRand); // 图象生效 g.dispose(); // 输出图象到页面 ImageIO.write(image, "JPEG", resp.getOutputStream()); } public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { doGet(request, response); } }JSP实现
<%@ page language="java" import="java.util.*" pageEncoding="utf-8"%> <% String path = request.getContextPath(); String basePath = request.getScheme() + "://" + request.getServerName() + ":" + request.getServerPort() + path + "/"; %> <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"> <html> <head> <base href="<%=basePath%>"> <title>My JSP 'index.jsp' starting page</title> <meta http-equiv="pragma" content="no-cache"> <meta http-equiv="cache-control" content="no-cache"> <meta http-equiv="expires" content="0"> <meta http-equiv="keywords" content="keyword1,keyword2,keyword3"> <meta http-equiv="description" content="This is my page"> <!-- <link rel="stylesheet" type="text/css" href="styles.css"> --> <script type="text/javascript"> function huan() { document.getElementById("img").src = "ImgServlet?tim=" + new Date().getTime(); } </script> </head> <body> <form action="UploadServlet" enctype="multipart/form-data" method="post"> <p> 姓名： <input name="username" /> </p> <p> 验证码： <input name="yanzheng" size="4" /> <img id="img" src="ImgServlet" /><a href="javascript:huan()">换一张</a> </p> <p> <input type="submit" value="上传" /> </p> </form> </body> </html>