如何使用异步servlet +非阻塞IO进行文件下载？

@WebServlet("/download")
public class DownloadServlet extends HttpServlet {
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // 设置异步请求的超时时间
        AsyncContext asyncContext = request.startAsync();
        asyncContext.setTimeout(0);

        // 设置响应的Content-Type和Content-Disposition头部
        response.setContentType("application/octet-stream");
        response.setHeader("Content-Disposition", "attachment; filename=\"example.txt\"");

        // 获取输出流
        ServletOutputStream outputStream = response.getOutputStream();

        // 使用非阻塞IO方式进行文件写入
        Path filePath = Paths.get("/path/to/example.txt");
        AsynchronousFileChannel fileChannel = AsynchronousFileChannel.open(filePath, StandardOpenOption.READ);
        ByteBuffer buffer = ByteBuffer.allocate(1024);
        fileChannel.read(buffer, 0, buffer, new CompletionHandler<Integer, ByteBuffer>() {
            public void completed(Integer result, ByteBuffer buffer) {
                buffer.flip();
                try {
                    outputStream.write(buffer.array(), 0, result);
                    buffer.clear();
                    if (result >= 0) {
                        fileChannel.read(buffer, fileChannel.position(), buffer, this);
                    } else {
                        fileChannel.close();
                        outputStream.close();
                        asyncContext.complete();
                    }
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }

            public void failed(Throwable exc, ByteBuffer buffer) {
                try {
                    fileChannel.close();
                    outputStream.close();
                    asyncContext.complete();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        });
    }
}