response.setContentType(CONTENT_TYPE);
response.setContentType("image/jpeg"); //必须设置ContentType为image/jpeg
int length = 4; //设置默认生成4个数字
Date d = new Date();
long lseed = d.getTime();
java.util.Random r = new Random(lseed); //设置随机种子
if (request.getParameter("length") != null) {
try {
length = Integer.parseInt(request.getParameter("length"));
}
catch (NumberFormatException e) {
}
}
StringBuffer str = new StringBuffer();
for (int i = 0; i <length; i++) {
str.append(r.nextInt(9)); //生成随机数字
}
//可以在此加入保存验证码的代码
//创建内存图像
BufferedImage bi = new BufferedImage(40, 16, BufferedImage.TYPE_INT_RGB);
Graphics2D g = bi.createGraphics();
g.clearRect(0, 0, 16, 40);
g.setColor(Color.green.CYAN);
g.drawString(str.toString(), 4, 12);
try {
//使用JPEG编码,输出到response的输出流
JPEGImageEncoder encoder = JPEGCodec.createJPEGEncoder(response.
getOutputStream());
JPEGEncodeParam param = encoder.getDefaultJPEGEncodeParam(bi);
param.setQuality(1.0f, false);
encoder.setJPEGEncodeParam(param);
encoder.encode(bi);
}
catch (Exception ex) {
}
}