code: private Boolean doValidations(final DragAndDropEvent dragEvent) {
          final Component compsource = dragEvent.getTransferable().getSourceComponent();
          Boolean isValid = Boolean.TRUE;
          if (compsource instanceof Table && !isComplexFilterViewDisplayed) {
              final TableTransferable transferable = (TableTransferable) dragEvent.getTransferable();
              final Table source = transferable.getSourceComponent();
  
              if (!source.getId().equals(UIComponentIdProvider.DIST_TABLE_ID)) {
                  notification.displayValidationError(i18n.getMessage(UIMessageIdProvider.MESSAGE_ACTION_NOT_ALLOWED));
                  isValid = Boolean.FALSE;
              } else {
                  if (getDropppedDistributionDetails(transferable).size() > 1) {
                      notification.displayValidationError(i18n.getMessage("message.onlyone.distribution.dropallowed"));
                      isValid = Boolean.FALSE;
                  }
              }
          } else {
              notification.displayValidationError(i18n.getMessage(UIMessageIdProvider.MESSAGE_ACTION_NOT_ALLOWED));
              isValid = Boolean.FALSE;
          }
          return isValid;
      }
docs: Validation for drag event.
  
  @param dragEvent
  @return