code: public void visit(final WebAppServlet webAppServlet) {
  		NullArgumentException.validateNotNull(webAppServlet, "Web app servlet");
  		Class<? extends Servlet> servletClass = webAppServlet
  				.getServletClass();
  		if (servletClass == null && webAppServlet.getServletClassName() != null) {
  			try {
  				servletClass = RegisterWebAppVisitorHS.loadClass(Servlet.class, bundleClassLoader,
  						webAppServlet.getServletClassName());
  			} catch (ClassNotFoundException | IllegalAccessException e) {
  				// TODO Auto-generated catch block
  				e.printStackTrace();
  			}
  		}
  		if (servletClass != null) {
  			//CHECKSTYLE:OFF
  			try {
  				webContainer.unregisterServlets(servletClass);
  				webAppServlet.setServletClass(null);
  			} catch (Exception ignore) {
  				LOG.warn("Unregistration exception. Skipping.", ignore);
  			}
  			//CHECKSTYLE:ON
  		}
  	}
docs: Unregisters servlet from web container.
  
  @throws NullArgumentException if servlet is null
  @see WebAppVisitor#visit(WebAppServlet)