JAVAweb文件下载功能支持断点续传并输出本次下载的数据量

    public void downloadExistsFile(HttpServletRequest request, HttpServletResponse response, File proposeFile) throws IOException, FileNotFoundException {
        response.reset();
        OutputStream outputStream=null;
        InputStream inputStream=null;
        log.debug("下载文件路径：" + proposeFile.getPath());
        response.setContentType("application/octet-stream");
        response.setHeader("Content-disposition", "attachment; filename=" + proposeFile.getName());
        response.setHeader("Accept-Ranges", "bytes");
        long currentLen = 0;// 已读取文件大小
        long totleLen = proposeFile.length();// 总文件大小
        long start=0;//读取的开始位置，默认0
        long end=proposeFile.length()-1;//读取的结束位置，默认读完
        if (null != request.getHeader("Range")) {
            // 断点续传
            // 若客户端传来Range，说明之前下载了一部分，设置206状态(SC_PARTIAL_CONTENT)
            response.setStatus(HttpServletResponse.SC_PARTIAL_CONTENT);
            try {
                String range = request.getHeader("Range");
                int index = range.indexOf("=");
                int ed = range.indexOf("-");
                start=Long.parseLong(range.substring(index + 1, ed));
                try {
                    end=Long.parseLong(range.substring(ed+1, range.length()));
                }catch (Exception e) {
                    //如果没有指定结束位置，则读完整个文件
                    end=proposeFile.length()-1;
                }
                //如果读取的结束位置大于文件长度，则结束位置设置为文件长度-1
                if (end>=proposeFile.length()){
                    end=proposeFile.length()-1;
                }
            } catch (NumberFormatException e) {
                log.error(request.getHeader("Range") + " is not Number!");
            }
        }
        //本次发送的文件长度
        Long rangeLength=end - start + 1;
        response.setHeader("Content-Length", String.valueOf(rangeLength));
        //本次读取文件的信息，包括开始位置，结束位置，文件总大小
        response.setHeader("Content-Range", String.format("bytes %s-%s/%s", start, end, proposeFile.length()));
        try {
            outputStream = response.getOutputStream();
            inputStream = new FileInputStream(proposeFile);
            inputStream.skip(start);
            byte[] buffer = new byte[5 * 1024];
            int length = 0;
            while (currentLen<rangeLength) {
                length=inputStream.read(buffer,0,(rangeLength-currentLen)<=buffer.length ?
                        (int)(rangeLength-currentLen) : buffer.length);
                currentLen+=length;
                outputStream.write(buffer,0,length);
            }
            outputStream.flush();
            log.info("本次下载量/本次需要下载的总大小{}/{}，文件总大小{}",currentLen,rangeLength,totleLen);
        }catch (Exception e){

            log.error("下载中断或者网络异常表示没下载完");
            log.info("本次下载量/本次需要下载的总大小{}/{}，文件总大小{}",currentLen,rangeLength,totleLen);
        }finally {
            if (outputStream != null) {
                outputStream.close();
            }
            if (inputStream != null) {
                inputStream.close();
            }
        }

    }