Amazon S3 文件系统断点下载

private void ossPathDownload(HttpServletResponse response, HttpServletRequest request, String ossPath) {
        log.info("oss下载path={}",ossPath);
        ObjectMetadata objectMetadata = amazonS3.getObjectMetadata(bucketName,ossPath);
        long contentLength = 0L;
        long p = 0L;
        long toLength = 0L;
        int rangeSwitch = 0; // 0,从头开始的全文下载；1,从某字节开始的下载（bytes=27000-）；2,从某字节开始到某字节结束的下载（bytes=27000-39000）
        long fileLength = objectMetadata.getContentLength();
        String rangBytes = "";
        // client requests a file block download start byte
        String range = request.getHeader("Range");
        if (range != null && range.trim().length() > 0 && !"null".equals(range)) {
            response.setStatus(HttpServletResponse.SC_PARTIAL_CONTENT);
            rangBytes = range.replaceAll("bytes=", "");
            if (rangBytes.endsWith("-")) {  // bytes=270000-
                rangeSwitch = 1;
                p = Long.parseLong(rangBytes.substring(0, rangBytes.indexOf("-")));
                contentLength = fileLength - p;  // 客户端请求的是270000之后的字节（包括bytes下标索引为270000的字节）
            } else { // bytes=270000-320000
                rangeSwitch = 2;
                String temp1 = rangBytes.substring(0, rangBytes.indexOf("-"));
                String temp2 = rangBytes.substring(rangBytes.indexOf("-") + 1, rangBytes.length());
                p = Long.parseLong(temp1);
                toLength = Long.parseLong(temp2);
                contentLength = toLength - p + 1; // 客户端请求的是 270000-320000 之间的字节
            }
        } else {
            contentLength = fileLength;
        }

        // 如果设设置了Content-Length，则客户端会自动进行多线程下载。如果不希望支持多线程，则不要设置这个参数。
        // Content-Length: [文件的总大小] - [客户端请求的下载的文件块的开始字节]
//                response.setHeader("Content-Length", new Long(contentLength).toString());
        GetObjectRequest getObjectRequest = new GetObjectRequest(bucketName,ossPath);
        // 断点开始
        // 响应的格式是:
        // Content-Range: bytes [文件块的开始字节]-[文件的总大小 - 1]/[文件的总大小]
        if (rangeSwitch == 1) {
            String contentRange = new StringBuffer("bytes ").append(new Long(p).toString()).append("-")
                    .append(new Long(fileLength - 1).toString()).append("/")
                    .append(new Long(fileLength).toString()).toString();
            response.setHeader("Content-Range", contentRange);
            getObjectRequest = getObjectRequest.withRange(p);
        } else if (rangeSwitch == 2) {
            String contentRange = range.replace("=", " ") + "/" + new Long(fileLength).toString();
            response.setHeader("Content-Range", contentRange);
            getObjectRequest = getObjectRequest.withRange(p,toLength);;
        } else {
            String contentRange = new StringBuffer("bytes ").append("0-")
                    .append(fileLength - 1).append("/")
                    .append(fileLength).toString();
            response.setHeader("Content-Range", contentRange);
        }

        response.setContentType("application/octet-stream");
        response.setCharacterEncoding("utf-8");
        S3Object s3Object = amazonS3.getObject(getObjectRequest);
        try (InputStream inputStream = s3Object.getObjectContent();
             OutputStream outputStream = response.getOutputStream()){
            String realFileName = URLEncoder.encode(ossPath.substring(ossPath.lastIndexOf("/")+1), "UTF-8");
            response.addHeader("Content-Disposition", "attachment;filename=" + realFileName);
            response.addHeader("fileSize",fileLength+"");
            response.addHeader("cache-control",cacheControl);
            IOUtils.copy(inputStream,outputStream);
        } catch (IOException e) {
            log.error(e.getMessage(),e);
        }
    }