验证码的生成，并且“看不清，换一张”

验证码的生成，并且“看不清，换一张” public class AuthImg extends HttpServlet { private static final String CONTENT_TYPE = ";text/html; charset=UTF-8";; private Font mFont; public AuthImg() { mFont = new Font(";Times New Roman";, 0, 18); } public void init() throws ServletException { } public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { String authCode = genAuthCode(4); AuthCodeCookie authCodeCookie = new AuthCodeCookie(request, response); authCodeCookie.addAuthCode(authCode);//???æÑéÖ?Âëµ?cookies response.setContentType(";image/jpeg";); javax.servlet.ServletOutputStream out = response.getOutputStream(); int width = 60; int height = 20; BufferedImage image = new BufferedImage(width, height, 1); Graphics gra = image.getGraphics(); Random random = new Random(); gra.setColor(getRandColor(200, 250)); gra.fillRect(1, 1, width, height); gra.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); gra.drawLine(x, y, x + xl, y + yl); } gra.setFont(mFont); for (int i = 0; i <; 4; i++) { char c = authCode.charAt(i); gra.setColor(new Color(20 + random.nextInt(110), 20 + random.nextInt(110), 20 + random.nextInt(110))); gra.drawString(String.valueOf(c), 13 * i + 6, 16); } gra.dispose(); ImageIO.write(image, ";JPEG";, out); } 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); } public String genAuthCode(int length) { if (length <; 1) return null; String strChars[] = { ";1";, ";2";, ";3";, ";4";, ";5";, ";6";, ";7";, ";8";, ";9"; }; StringBuffer strPassword = new StringBuffer(); int nRand = (int) Math.round(Math.random() * 100D); for (int i = 0; i <; length; i++) { nRand = (int) Math.round(Math.random() * 100D); strPassword.append(strChars[nRand % (strChars.length - 1)]); } return strPassword.toString(); } public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { doGet(request, response); } public void destroy() { } } html: function refresh() { var img = document.getElementById(";checkCodeImg";); now = new Date(); img.src = ";authimg?code=";+now.getTime(); } <;IMG height=18 src='authimg' id=";checkCodeImg"; >; <;a href=";#"; onclick=";javascript:refresh();";>;????Çå,??Ò?ÕÅ<;/a>; web.xml: <;servlet>;     <;servlet-name>;authimg<;/servlet-name>;     <;servlet-class>;com.worthtech.app.servlet.AuthImg<;/servlet-class>;   <;/servlet>;   <;servlet-mapping>;     <;servlet-name>;authimg<;/servlet-name>;     <;url-pattern>;/authimg<;/url-pattern>;   <;/servlet-mapping>;