code: public void visit(final WebAppListener webAppListener) {
  		NullArgumentException.validateNotNull(webAppListener,
  				"Web app listener");
  		try {
  			final EventListener listener = RegisterWebAppVisitorHS.newInstance(
  					EventListener.class, bundleClassLoader,
  					webAppListener.getListenerClass());
  			webAppListener.setListener(listener);
  			webContainer.registerEventListener(listener, httpContext);
  			//CHECKSTYLE:OFF
  		} catch (Exception ignore) {
  			LOG.error(REGISTRATION_EXCEPTION_SKIPPING, ignore);
  		}
  		//CHECKSTYLE:ON
  	}
docs: Registers listeners with web container.
  
  @throws NullArgumentException if listener is null
  @see WebAppVisitor#visit(org.ops4j.pax.web.extender.war.internal.model.WebAppListener)