How to persist an entity inside an event listener?

Is it possible to persist an entity inside an event listener? I'm trying to implement an audit trail feature:

public function preUpdate($eventArgs)
{
  if ($eventArgs->getEntity() instanceof \Domain\Entity\Customer) {
    $customerAuditTrail = new \Domain\Entity\CustomerAuditTrail();

    if ($eventArgs->hasChangedField('FirstName')) {
      $customerAuditTrail->setAction('Update');
      $customerAuditTrail->setField('FirstName');
      $customerAuditTrail->setCustomer($eventArgs->getEntity());

      $customerAuditTrail->setOldValue($eventArgs->getOldValue('FirstName'));
      $customerAuditTrail->setNewValue($eventArgs->getNewValue('FirstName'));
      ...

      $this->_em->persist($cus开发者_如何学PythontomerAuditTrail);
    }
  }
}

The save operation is working fine but the customerAuditTrail has not been persisted in the database.

You can insert other entities in onFlush event, you can see an example in http://www.doctrine-project.org/blog/doctrine2-versionable