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1.说明

        大视频的在线预览,如果不支持断点下载,将无法在苹果手机上播放,同时不支持进度条拖动.

        之所以这样,是因为视频文件太大了,通过二进制流向浏览器传输时,整个文件尚未传输完成时,会被浏览器强制关闭流,不再接收,等缓存播放到一定程度时,浏览器会再次向后端请求视频文件,同时附带range参数,指定获取数据范围,后端需支持对range参数的处理.

2.代码

    @ResponseBody@GetMapping(value = "/preview")@Operation(summary = "在线预览", description = "文件在浏览器中预览")public void Preview(@RequestParam String fileInfoId, HttpServletRequest request, HttpServletResponse response) throws Exception {//获取存储文件var fileInfo = fileInfoService.Get(fileInfoId);if (fileInfo == null) {response.sendError(HttpServletResponse.SC_NOT_FOUND, "File not found!");return;}//设置页面缓存if (MisFileType.PICTURE.equals(fileInfo.getFile_type()) || MisFileType.TEXT.equals(fileInfo.getFile_type())) {response.setHeader("Cache-Control", "max-age=60");//页面缓存时间60秒}//断点下载ResumeDownload(request, response, fileInfo, "inline");}/*** 支持断点重新下载文件** @param fileInfo    文件* @param disposition 下载方式 inline:内嵌 attachment:附件*/private static void ResumeDownload(HttpServletRequest request, HttpServletResponse response,FileInfoOutput fileInfo, String disposition) throws IOException {//获取存储文件String storageFilePath = FileConfig.Path + File.separator + fileInfo.getFile_path();File storageFile = new File(storageFilePath);if (!StringUtils.hasLength(storageFilePath) || !storageFile.exists()) {//相对路径未找到文件storageFilePath = fileInfo.getFile_absolute_path();//根据绝对路径寻找文件storageFile = new File(storageFilePath);if (!StringUtils.hasLength(storageFilePath) || !storageFile.exists()) {response.sendError(HttpServletResponse.SC_NOT_FOUND, "File not found!");return;}}//推断类型String mimeType = Files.probeContentType(storageFile.toPath());if (!StringUtils.hasLength(mimeType)) {URL url = new URL("file:///" + storageFilePath);mimeType = url.openConnection().getContentType();}//下载开始位置long startByte = 0;//下载结束位置long endByte = storageFile.length() - 1;//获取下载范围String range = request.getHeader("range");if (range != null && range.contains("bytes=") && range.contains("-")) {range = range.substring(range.lastIndexOf("=") + 1).trim();String[] rangeArray = range.split("-");if (rangeArray.length == 1) {//Example: bytes=1024-if (range.endsWith("-")) {startByte = Long.parseLong(rangeArray[0]);} else { //Example: bytes=-1024endByte = Long.parseLong(rangeArray[0]);}}//Example: bytes=2048-4096else if (rangeArray.length == 2) {startByte = Long.parseLong(rangeArray[0]);endByte = Long.parseLong(rangeArray[1]);}}long contentLength = endByte - startByte + 1;//HTTP 响应头设置//断点续传，HTTP 状态码必须为 206，否则不设置，如果非断点续传设置 206 状态码，则浏览器无法下载if (range != null) {log.trace("断点下载range:{},总大小:{},{}({})", range, storageFile.length(), fileInfo.getFile_name(), fileInfo.getId());response.setStatus(HttpServletResponse.SC_PARTIAL_CONTENT);}if (StringUtils.hasLength(mimeType)) {response.setContentType(mimeType);response.setHeader("Content-Type", mimeType);}response.setHeader("Content-Length", String.valueOf(contentLength));response.setHeader("Accept-Ranges", "bytes");//Content-Range: 下载开始位置-下载结束位置/文件大小response.setHeader("Content-Range", "bytes " + startByte + "-" + endByte + "/" + storageFile.length());//Content-disposition: inline; filename=xxx.xxx 表示浏览器内嵌显示该文件response.setHeader("Content-Disposition", disposition + "; filename=" + URLEncoder.encode(fileInfo.getFile_name(), StandardCharsets.UTF_8));//传输文件流BufferedOutputStream outputStream = null;RandomAccessFile randomAccessFile = null;//已传送数据大小long transmittedLength = 0;try {//以只读模式设置文件指针偏移量randomAccessFile = new RandomAccessFile(storageFile, "r");randomAccessFile.seek(startByte);outputStream = new BufferedOutputStream(response.getOutputStream());byte[] buff = new byte[4096];int len;while (transmittedLength < contentLength && (len = randomAccessFile.read(buff)) != -1) {outputStream.write(buff, 0, len);transmittedLength += len;}outputStream.flush();response.flushBuffer();log.trace("下载完毕:{}-{},下载量:{},总大小:{},{}({})", startByte, endByte, transmittedLength,storageFile.length(), fileInfo.getFile_name(), fileInfo.getId());} catch (IOException e) {if (StringUtils.hasLength(range)) {response.setHeader("Content-Range", "bytes " + startByte + "-" + startByte + transmittedLength + "/" + storageFile.length());log.trace("断点下载完毕:{}-{},下载量:{},总大小:{},{}({})", startByte, endByte, transmittedLength, storageFile.length(),fileInfo.getFile_name(), fileInfo.getId());} else {log.info("下载停止:{}-{},下载量:{},总大小:{},{}({})", startByte, endByte, transmittedLength, storageFile.length(),fileInfo.getFile_name(), fileInfo.getId());}} finally {try {if (randomAccessFile != null) {randomAccessFile.close();}} catch (IOException e) {log.error("下载异常," + fileInfo.getId(), e);}}}