@SuppressWarnings("resource")public void download() throws Exception{    String filename = "qrcode.png";    String content = "content";    BufferedImage image = QRcodeUtils.encode(content, size);        //BufferedImage 转 InputStream    ByteArrayOutputStream byteArrayOutputStream = new ByteArrayOutputStream();    ImageOutputStream imageOutput = ImageIO.createImageOutputStream(byteArrayOutputStream);    ImageIO.write(image, "png", imageOutput);    InputStream inputStream = new ByteArrayInputStream(byteArrayOutputStream.toByteArray());    long length = imageOutput.length();        //设置response    HttpServletResponse response = this.getResponse();    response.setContentType("application/x-msdownload");    response.setContentLength((int)length);    response.setHeader("Content-Disposition","attachment;filename="+new String(filename.getBytes("gbk"),"iso-8859-1"));        //输出流    byte[] bytes = new byte[1024];    OutputStream outputStream = response.getOutputStream();    long count = 0;    while(count < length){        int len = inputStream.read(bytes, 0, 1024);        count +=len;        outputStream.write(bytes, 0, len);    }    outputStream.flush();}