Customer/EventListener/CustomerListener.php
public function onUpdate(ResourceEventInterface $event)
    {
        $customer = $this->getCustomerFromEvent($event);

        $changed = $this->generateNumber($customer);

        if ($this->persistenceHelper->isChanged($customer, 'parent')) {
            $changed |= $this->updateFromParent($customer);
        }

        $changed |= $this->pricingUpdater->updateVatNumberSubject($customer);

        if ($changed) {
            $this->persistenceHelper->persistAndRecompute($customer);
        }

        $hierarchyFields = ['company', 'customerGroup', 'vatNumber', 'vatDetails', 'vatValid'];
        if ($this->persistenceHelper->isChanged($customer, $hierarchyFields)) {
            $this->scheduleParentChangeEvents($customer);
        }
    }
public function onUpdate(ResourceEventInterface $event)
    {
        $customer = $this->getCustomerFromEvent($event);

        $changed = $this->generateNumber($customer);

        if ($this->persistenceHelper->isChanged($customer, 'parent')) {
            $changed |= $this->updateFromParent($customer);
        }

        $changed |= $this->pricingUpdater->updateVatNumberSubject($customer);

        if ($changed) {
            $this->persistenceHelper->persistAndRecompute($customer);
        }

        $hierarchyFields = ['company', 'customerGroup', 'vatNumber', 'vatDetails', 'vatValid'];
        if ($this->persistenceHelper->isChanged($customer, $hierarchyFields)) {
            $this->scheduleParentChangeEvents($customer);
        }
    }
Update event handler.

@param ResourceEventInterface $event