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.

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