code: @Override
      public void updateProgress(final long readBytes, final long contentLength) {
          if (readBytes > maxSize || contentLength > maxSize) {
              LOG.error("User tried to upload more than was allowed ({}).", maxSize);
              interruptUploadDueToFileSizeExceeded(maxSize);
              return;
          }
          if (isUploadInterrupted()) {
              // Upload interruption is delayed maybe another event is fired
              // before
              return;
          }
  
          publishUploadProgressEvent(fileUploadId, readBytes, contentLength);
      }
docs: Reports progress in {@link Upload} variant.
  
  @see com.vaadin.ui.Upload.ProgressListener#updateProgress(long, long)