public static  void enableHibernateSearch(EventListeners listeners,
    Properties properties) 
{
	                      	 
		// check whether search is explicitly disabled - if so there is nothing to do	
		String enableSearchListeners = properties.getProperty( Environment.AUTOREGISTER_LISTENERS );
		if ( "false".equalsIgnoreCase( enableSearchListeners ) ) {
			log.info(
					"Property hibernate.search.autoregister_listeners is set to false." +
							" No attempt will be made to register Hibernate Search event listeners."
			);
			return;
		}
		final FullTextIndexEventListener searchListener = new FullTextIndexEventListener();
		// PostInsertEventListener
		listeners.setPostInsertEventListeners(
				addIfNeeded(
						listeners.getPostInsertEventListeners(),
						searchListener,
						new PostInsertEventListener[] { searchListener }
				)
		);
		// PostUpdateEventListener
		listeners.setPostUpdateEventListeners(
				addIfNeeded(
						listeners.getPostUpdateEventListeners(),
						searchListener,
						new PostUpdateEventListener[] { searchListener }
				)
		);
		// PostDeleteEventListener
		listeners.setPostDeleteEventListeners(
				addIfNeeded(
						listeners.getPostDeleteEventListeners(),
						searchListener,
						new PostDeleteEventListener[] { searchListener }
				)
		);
		// PostCollectionRecreateEventListener
		listeners.setPostCollectionRecreateEventListeners(
				addIfNeeded(
						listeners.getPostCollectionRecreateEventListeners(),
						searchListener,
						new PostCollectionRecreateEventListener[] { searchListener }
				)
		);
		// PostCollectionRemoveEventListener
		listeners.setPostCollectionRemoveEventListeners(
				addIfNeeded(
						listeners.getPostCollectionRemoveEventListeners(),
						searchListener,
						new PostCollectionRemoveEventListener[] { searchListener }
				)
		);
		// PostCollectionUpdateEventListener
		listeners.setPostCollectionUpdateEventListeners(
				addIfNeeded(
						listeners.getPostCollectionUpdateEventListeners(),
						searchListener,
						new PostCollectionUpdateEventListener[] { searchListener }
				)
		);
}

Add the FullTextIndexEventListener to all listeners, if enabled in configuration and if not already registered.