文件分段后，进行分片上传逻辑

    public static void startMultiPartUpload(String file)
    {
        RandomAccessFile randomAccessFile = null;
        RandomAccessFile  out = null;
        try{
            out = new RandomAccessFile("D:\\data\\xxxx", "rw");
            randomAccessFile = new RandomAccessFile(file, "rw");
            long fileLength = randomAccessFile.length();
            //每个分块为1M
            int chunkSize = 1024 * 1024;
            byte[] chunkData = new byte[chunkSize];
            int offset = 0;
            int readLen = 0;
            while (true)
            {
                if (offset >= fileLength) {                                             //当offset偏移与文件长度一致时，停止循环
                    break;
                }
                //将指针指向最新的偏移位
                randomAccessFile.seek(offset);
                if ((readLen = randomAccessFile.read(chunkData, 0, chunkSize)) == -1)   //其实此处返回的长度为实际读取到字节数组中的长度
                {
                    break;
                }

                if(readLen < chunkSize){                                                 //字节数组没有填充满时，进行实际长度的填充
                    byte[] realChunkData = new byte[readLen];
                    System.arraycopy(chunkData, 0, realChunkData, 0, readLen);
                    chunkData = realChunkData;
                }


                out.write(chunkData);



                offset = offset + readLen;
            }
        }catch(Exception e){
            e.printStackTrace();
        }finally {
            try {
                randomAccessFile.close();
                out.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }

    }