@PostMapping("returnStream")
    public void returnStream(HttpServletResponse response) throws IOException {
        String message = "我是一段等待已流形式返回的文字";
        // 以流的形式返回
        ServletOutputStream out = null;
        ByteArrayOutputStream baos = null;
        try {
            InputStream inStream = new ByteArrayInputStream(message.getBytes());
            byte[] buffer = new byte[1024];
            int len;
            baos = new ByteArrayOutputStream();
            while ((len = inStream.read(buffer)) != -1) {
                baos.write(buffer, 0, len);
            }
            out = response.getOutputStream();
            out.write(baos.toByteArray());
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            Objects.requireNonNull(baos).flush();
            baos.close();
            Objects.requireNonNull(out).flush();
            out.close();
        }
 
    }

		ServletOutputStream out = null;
		ByteArrayOutputStream baos = null;
		try {
			File file=new File(filename);
			InputStream inStream=new FileInputStream(file);
			byte[] buffer = new byte[1024];
			int len;
			baos = new ByteArrayOutputStream();
			while ((len = inStream.read(buffer)) != -1) {
				baos.write(buffer, 0, len);
			}
			out = response.getOutputStream();
			out.write(baos.toByteArray());
		} catch (Exception e) {
			e.printStackTrace();
		} finally {
			baos.flush();
			baos.close();
			out.flush();
			out.close();
		}