客户端每次请求取大文件部分数据。
浏览器播放mp4视频时，会首先传Range消息头，检测到206状态码，和Content-Range，Accept-Ranges 会自动请求余下数据。后端需要在文件任意偏移量取数据。
参考：
springboot项目实现断点续传功能_java_脚本之家
springboot大文件上传、分片上传、断点续传、秒传的实现_java_脚本之家
springboot 大文件上传、分片上传、断点续传、秒传_getmodelrw-CSDN博客
https://juejin.cn/post/7387915277318520869
在SpringBoot中实现断点续传的实例代码_java_脚本之家
主要代码：
private void videoPlayRange(String taskCode, String fileName) {File file = getVideoFile(taskCode, fileName);long fileLength = file.length();String range = request.getHeader("Range");long start = 0, end = fileLength - 1;if (range != null) {String[] ranges = range.replace("bytes=", "").split("-");start = Long.parseLong(ranges[0]);end = Math.min(fileLength - 1,start + maxPartSize*1024*1024-1);end = ranges.length > 1 ? Long.parseLong(ranges[1]) : end;}// Set the content type and attachment header.
// String contentType = request.getServletContext().getMimeType(video.getFile().getAbsolutePath());response.setContentType("video/mp4");
// response.setHeader(HttpHeaders.CONTENT_DISPOSITION, "attachment; filename=" + fileName);response.setHeader(HttpHeaders.ACCEPT_RANGES, "bytes");response.setHeader(HttpHeaders.CONTENT_RANGE, "bytes " + start + "-" + end + "/" + fileLength);response.setHeader(HttpHeaders.CONTENT_LENGTH, String.valueOf(end - start + 1));response.setStatus(206);
// headers.setContentType(MediaType.parseMediaType(contentType));// Create resource that represents the part of the video file.try (RandomAccessFile raf = new RandomAccessFile(file, "r")){raf.seek(start);ServletOutputStream out = response.getOutputStream();byte[] bytes = new byte[4096];int r = 0;while (start<=end) {r = raf.read(bytes,0,(int)Math.min(bytes.length,end-start+1));if(r<=0){break;}start+=r;out.write(bytes,0,r);}} catch (Exception e) {throw new RuntimeException(e);}}
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