浏览器Content-Range断点续传MP4文件

@RequestMapping("/file/get")
public void download(@RequestHeader(value = "origin", defaultValue = "") String origin, @RequestHeader(value = "User-Agent", defaultValue = "") String userAgent, @RequestHeader(value = "Range", defaultValue = "") String range, @RequestParam(value = "filePath", defaultValue = "") String filePath, HttpServletResponse resp) {
    // 参数错误
    if (StringUtils.isEmpty(filePath)) {
        WebUtils.sendError(resp, HttpStatus.BAD_REQUEST_400, "Parameter - `filePath` missing");
        return;
    }
    log.info("range:{} , user-agent:{}", range, userAgent);
    String fileName = new File(fileKey.trim()).getName();
    if (!StringUtils.isEmpty(fileName)) {
    	//添加文件名称
        resp.addHeader("Content-Disposition", String.format("inline; filename=\"%s\"", fileName));
        //根据文件后缀名添加文件类型
        Optional<MediaType> optionalMediaType = MediaTypeFactory.getMediaType(fileName);
        optionalMediaType.ifPresent(mediaType -> resp.addHeader(HttpHeader.CONTENT_TYPE.asString(), mediaType.toString()));
    }
    String rule = WebUtils.getMatchAllowRule(origin, GlobalVar.getInstance().getAllowRules());
    if (null != rule) {
    	//跨域域名英文【,】逗号隔开
        resp.addHeader("Access-Control-Allow-Origin", rule);
        //支持的方法
        resp.addHeader("Access-Control-Allow-Methods", "GET, POST");
        //不允许跨域Cookies等信息
        resp.addHeader("Access-Control-Allow-Credentials", "false");
        //自定义头部
        resp.addHeader("Access-Control-Allow-Headers", "X-Custom-Header");
    }
    shardFile(range, resp);
}

private void shardFile(String rangeStr,String filePath, HttpServletResponse response) {
    // 起始偏移量，可以根据请求参数来设置
    long offset = 0L;
    long length = 102400L;
    File file = new File(filePath);
    long totalSize = file.length();
    if (StringUtils.isNotEmpty(rangeStr)) {
        offset = Long.valueOf(rangeStr.replace("bytes=", "").split("-")[0]);
        // 每次读取的长度，可以根据请求参数或文件大小来设置
        // 检查偏移量和长度是否有效
        if (offset < 0 || offset >= totalSize) {
            response.setStatus(HttpServletResponse.SC_BAD_REQUEST);
            return;
        }
        if (length <= 0 || offset + length > totalSize) {
            length = totalSize - offset;
        }
    }
	//浏览器断点续传，应答状态是206，需要显示设置，不是200，非常重要
    response.setStatus(HttpServletResponse.SC_PARTIAL_CONTENT);
	//返回当前这一次读取的长度，不是文件总大小
    response.addHeader("Content-Length", String.valueOf(length));
	//文件返回方式，bytes
    response.setHeader("Accept-Ranges", "bytes");
	//浏览器探测到后端返回Content-Range，支持断点续传，会立即终止前面一个连接，报错，连接CLOSE，格式 【bytes 开始offset0开始-结束索引（长度-1）+开始索引】/文件总长度
    String newRangStr = new StringBuffer("bytes ").append(offset).append("-").append((offset + length - 1)).append("/").append(totalSize).toString();
    //文件支持断点续传
	ponse.setHeader("Content-Range", newRangStr);
    try (InputStream is = new BufferedInputStream(new FileInputStream(file))) {
        is.skip(offset);
        byte[] buffer = new byte[10240];
        int readSize = buffer.length;
        int sumSize = 0;
        while (true) {
            if (readSize <= 0) {
                break;
            }
            readSize = is.read(buffer, 0, readSize);
            try {
                response.getOutputStream().write(buffer, 0, readSize);
            } catch (IOException e) {
				//报错连接关闭，不用管
            }
            sumSize += readSize;
            if (sumSize + readSize > length) {
                readSize = (int) (length - sumSize);
            } else if (sumSize >= length) {
                break;
            }
        }
    } catch (Exception e) {
        log.warn("写入失败", e);
    }
}