Prevent invalid entities from being updated

ValidatorListener.php

<?php

namespace Acme\DemoBundle\EventListener;

use Symfony\Component\Validator\Validator;
use Doctrine\ORM\Event\LifecycleEventArgs;

/**
 * Prevent invalid entities from being updated
 *
 * Here is an example on how to define your listener in yaml format:
 * cognard_user.listener.validator_listener:
 *     class: Acme\DemoBundle\EventListener\ValidatorListener
 *     arguments:
 *         - @validator
 *     tags:
 *         - { name: doctrine.event_listener, event: preUpdate }
 *     public: false
 *
 * @author Jérôme Cognard <jerome.cognard@gmail.com>
 */
class ValidatorListener
{

    /**
     * @var \Symfony\Component\Validator\Validator
     */
    private $validator;


    /**
     * @param \Symfony\Component\Validator\Validator $validator
     */
    public function __construct(Validator $validator)
    {
        $this->validator = $validator;
    }

    /**
     * @param \Doctrine\ORM\Event\LifecycleEventArgs $args
     */
    public function preUpdate(LifecycleEventArgs $args)
    {
        $entity = $args->getEntity();
        $errors = $this->validator->validate($entity);

        // If entity is invalid
        if (count($errors) > 0) {
            $em = $args->getEntityManager();
            $uw = $em->getUnitOfWork();

            // Clear changes
            $uw->clearEntityChangeSet(spl_object_hash($entity));
        }
    }

}