解析本地视频，以流文件给前端播放

String file = urlConfig.getLocalDir()+videoId+".mp4";
       RandomAccessFile randomFile = new RandomAccessFile(new File(file), "r");//只读模式
   long contentLength = randomFile.length();
       String range = request.getHeader("Range");
       int start = 0, end = 0;
       if(range != null && range.startsWith("bytes=")){
           String[] values = range.split("=")[1].split("-");
           start = Integer.parseInt(values[0]);
           if(values.length > 1){
               end = Integer.parseInt(values[1]);
           }
       }
       int requestSize = 0;
       if(end != 0 && end > start){
           requestSize = end - start + 1;
       } else {
           requestSize = Integer.MAX_VALUE;
       }

       byte[] buffer = new byte[4096];
       response.setContentType("video/mp4");
       response.setHeader("Accept-Ranges", "bytes");
       response.setHeader("ETag", videoId);
       response.setHeader("Last-Modified", new Date().toString());
       //第一次请求只返回content length来让客户端请求多次实际数据
       if(range == null){
           response.setHeader("Content-length", contentLength + "");
       }else{
           //以后的多次以断点续传的方式来返回视频数据
           response.setStatus(HttpServletResponse.SC_PARTIAL_CONTENT);//206
           long requestStart = 0, requestEnd = 0;
           String[] ranges = range.split("=");
           if(ranges.length > 1){
               String[] rangeDatas = ranges[1].split("-");
               requestStart = Integer.parseInt(rangeDatas[0]);
               if(rangeDatas.length > 1){
                   requestEnd = Integer.parseInt(rangeDatas[1]);
               }
           }
           long length = 0;
           if(requestEnd > 0){
               length = requestEnd - requestStart + 1;
               response.setHeader("Content-length", "" + length);
               response.setHeader("Content-Range", "bytes " + requestStart + "-" + requestEnd + "/" + contentLength);
           }else{
               length = contentLength - requestStart;
               response.setHeader("Content-length", "" + length);
               response.setHeader("Content-Range", "bytes "+ requestStart + "-" + (contentLength - 1) + "/" + contentLength);
           }
       }
       ServletOutputStream out = response.getOutputStream();
       int needSize = requestSize;
       randomFile.seek(start);
       while(needSize > 0){
           int len = randomFile.read(buffer);
           if(needSize < buffer.length){
               out.write(buffer, 0, needSize);
           } else {
               out.write(buffer, 0, len);
               if(len < buffer.length){
                   break;
               }
           }
           needSize -= buffer.length;
       }
       randomFile.close();
       out.close();
   
}