刷新显示验证码的页面后，在后台发现生成了两次验证码，页面显示的是第一次生成的验证码，用firebug查看，发现传回来的是第二次生成的验证码。非常费解为什么会生成两次验证码！！！！！！！！！！而且页面显示的还不是第二次生成的验证码。
下面是验证码的javabean:
- Java code
public final class Captcha { private String imgType = "png"; private String sessionWord = "captchaWord"; private int height = 20; private int width = 130; public Captcha() { } /** * 检查给出的验证码是否和session中的一致 * * @param session * @param word * @return */ @SuppressWarnings("rawtypes") public boolean checkWord(Map session, String word) { if (session == null || word == null) return false; String given = this.encryptsWord(word); Object o = session.get(this.sessionWord); String recorded = (o != null) ? (String) o : ""; if (recorded.equals(given)) return true; return false; } /** * 生成图片输出到输出流,并将加密后的验证码写到session * * @param session * @param os */ @SuppressWarnings("rawtypes") public void generateImage(Map session, OutputStream os) { if (session == null || os == null) throw new ExceptionInInitializerError("OutputStream required!"); BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB); Graphics g = image.getGraphics(); g.setColor(new Color(0xDCDCDC)); g.fillRect(0, 0, width, height); g.setColor(Color.black); g.drawRect(0, 0, width - 1, height - 1); String strEnsure = this.generateWord(); System.out.println("加密前的验证码是："+strEnsure); this.recordWord(session, strEnsure); g.setColor(Color.black); g.setFont(new Font("Atlantic Inline", Font.PLAIN, 18)); String str = strEnsure.substring(0, 1); g.drawString(str, 38, 17); str = strEnsure.substring(1, 2); g.drawString(str, 50, 15); str = strEnsure.substring(2, 3); g.drawString(str, 65, 18); str = strEnsure.substring(3, 4); g.drawString(str, 75, 15); Random random = new Random(); for (int i = 0; i < 150; i++) { int x = random.nextInt(width); int y = random.nextInt(height); g.drawOval(x, y, 1, 1); } g.dispose(); try { ImageIO.write(image, this.imgType, os); os.flush(); os.close(); } catch (IOException e) { e.printStackTrace(); } } /** * 对需要记录的串进行加密 * * @param word * 原始字符串 * @return */ private String encryptsWord(String word) { if (word == null) return null; String result = null; try { result = MyMD5.MD5encode(word); } catch (NoSuchAlgorithmException e) { e.printStackTrace(); } return result; } /** * 将验证码保存到session * * @param word * @param session */ @SuppressWarnings({ "rawtypes", "unchecked" }) private void recordWord(Map session, String word) { if (session == null) throw new RuntimeException("method recordWord require session"); session.put(this.sessionWord, this.encryptsWord(word)); } /** * 生成4位随机的验证码 * * @return */ @SuppressWarnings("rawtypes") private String generateWord() { String[] beforeShuffle = new String[] { "2", "3", "4", "5", "6", "7", "8", "9", "A", "B", "C", "D", "E", "F", "G", "H", "I", "J", "K", "L", "M", "N", "O", "P", "Q", "R", "S", "T", "U", "V", "W", "X", "Y", "Z" }; List list = Arrays.asList(beforeShuffle); Collections.shuffle(list); StringBuffer sb = new StringBuffer(); for (int i = 0; i < list.size(); i++) { sb.append(list.get(i)); } return sb.toString().substring(5, 9); }}