class HalPublicationBlock extends BlockBase implements BlockPluginInterface
{

  /**
   * {@inheritdoc}
   */
  public function build()
  {
        //do contain id but not bid
        $config = $this->getConfiguration();
        //$bid=$this->get->?

/**
 * {@inheritdoc}
 */
public function blockSubmit($form, FormStateInterface $form_state) {
  $block_id = $form['id']['#default_value'];
  $this->configuration['block_class'] = $block_id;
}

$formObject = $form_state->getFormObject()

/** @var DrupalblockBlockInterface $block */
$block = $formObject->getEntity();