每天学习点 验证码之Jcaptcha
如图：



代码：

ByteArrayOutputStream jpgout = new ByteArrayOutputStream();String id = req.getSession().getId();BufferedImage bimg = new DefaultManageableImageCaptchaService().getImageChallengeForID(id,req.getLocale());JPEGImageEncoder imgcode = JPEGCodec.createJPEGEncoder(jpgout);imgcode.encode(bimg);byte[] captchaChallengeAsJpeg = jpgout.toByteArray();resp.setHeader("Cache-Control", "no-store");resp.setHeader("Pragma", "no-cache");resp.setDateHeader("Expires", 0);resp.setContentType("image/jpeg");ServletOutputStream responseOutputStream = resp.getOutputStream();responseOutputStream.write(captchaChallengeAsJpeg);responseOutputStream.flush();responseOutputStream.close();