JavaExecutorGRPCClient.java

 FileInputStream fis = new FileInputStream(System.getProperty("java.io.tmpdir")+ File.separator+fileName);
          int bufferSize = 256 * 1024;
          while ((length = bis.read(buffer, 0, bufferSize)) != -1) {
                requestObserver.onNext(
                        UploadFileRequest.newBuilder().setFileContent(ByteString.copyFrom(buffer, 0, length)).build()
                );
requestObserver.onCompleted();
            finishLatch.await(1, TimeUnit.MINUTES);