Doctrine doesn't load associations from session correctly - php

Question

I'm having this behavior with Doctrine 2.1 where I'm looking for a nice 'workaround'. The problem is as follows:
I have a user Entity:
/**
* #Entity(repositoryClass="Application\Entity\Repository\UserRepository")
* #HasLifecycleCallbacks
*/
class User extends AbstractEntity
{
/**
*
* #var integer
*
* #Column(type="integer",nullable=false)
* #Id
* #GeneratedValue(strategy="IDENTITY")
*/
protected $id;
/**
*
* #var \DateTime
* #Column(type="datetime",nullable=false)
*/
protected $insertDate;
/**
*
* #var string
* #Column(type="string", nullable=false)
*/
protected $username;
/**
*
* #ManyToOne(targetEntity="UserGroup", cascade={"merge"})
*/
protected $userGroup;
}
And a usergroup entity:
/**
* #Entity
*/
class UserGroup extends AbstractEntity
{
/**
*
* #var integer
*
* #Column(type="integer",nullable=false)
* #Id
* #GeneratedValue(strategy="IDENTITY")
*/
protected $id;
/**
*
* #var string
* #Column(type="string",nullable=false)
*/
protected $name;
}
If I instantiate a user object (doing this with Zend_Auth) and Zend_Auth puts it automatically the session.
The problem is however, that is I pull it back from the session at a next page then the data in the user class is perfectly loaded but not in the userGroup association. If I add cascade={"merge"} into the annotation in the user object the userGroup object IS loaded but the data is empty. If you dump something like:
$user->userGroup->name
You will get NULL back. The problem is no data of the usergroup entity is accesed before the user object is saved in the session so a empty initialized object will be returned. If I do something like:
echo $user->userGroup->name;
Before I store the user object in the session all data of the assocication userGroup is succesfully saved and won't return NULL on the next page if I try to access the $user->userGroup->name variable.
Is there a simple way to fix this? Can I manually load the userGroup object/association with a lifecycle callback #onLoad in the user class maybe? Any suggestions?

Answer 1

Your problem is a combination of what mjh_ca answered and a problem with your AbstractEntity implementation.
Since you show that you access entity fields in this fashion:
$user->userGroup->name;
I assume your AbstractEntity base class is using __get() and __set() magic methods instead of proper getters and setters:
function getUserGroup()
{
return $this->userGroup;
}
function setUserGroup(UserGroup $userGroup)
{
$this->userGroup = $userGroup;
}
You are essentially breaking lazy loading:
"... whenever you access a public property of a proxy object that hasn’t been initialized yet the return value will be null. Doctrine cannot hook into this process and magically make the entity lazy load."
Source: Doctrine Best Practices: Don't Use Public Properties on Entities
You should instead be accessing fields this way:
$user->getUserGroup()->getName();
The second part of your problem is exactly as mjh_ca wrote - Zend_Auth detaches your entity from the entity manager when it serializes it for storage in the session. Setting cascade={"merge"} on your association will not work because it is the actual entity that is detached. You have to merge the deserialized User entity into the entity manager.
$detachedIdentity = Zend_Auth::getInstance()->getIdentity();
$identity = $em->merge($detachedIdentity);
The question, is how to do this cleanly. You could look into implementing a __wakeup() magic method for your User entity, but that is also against doctrine best practices...
Source: Implementing Wakeup or Clone
Since we are talking about Zend_Auth, you could extend Zend_Auth and override the getIdentity() function so that it is entity aware.
use Doctrine\ORM\EntityManager,
Doctrine\ORM\UnitOfWork;
class My_Auth extends \Zend_Auth
{
protected $_entityManager;
/**
* override otherwise self::$_instance
* will still create an instance of Zend_Auth
*/
public static function getInstance()
{
if (null === self::$_instance) {
self::$_instance = new self();
}
return self::$_instance;
}
public function getEntityManager()
{
return $this->_entityManager;
}
public function setEntityManager(EntityManager $entityManager)
{
$this->_entityManager = $entityManager;
}
public function getIdentity()
{
$storage = $this->getStorage();
if ($storage->isEmpty()) {
return null;
}
$identity = $storage->read();
$em = $this->getEntityManager();
if(UnitOfWork::STATE_DETACHED === $em->getUnitOfWork()->getEntityState($identity))
{
$identity = $em->merge($identity);
}
return $identity;
}
}
And than add an _init function to your Bootstrap:
public function _initAuth()
{
$this->bootstrap('doctrine');
$em = $this->getResource('doctrine')->getEntityManager();
$auth = My_Auth::getInstance();
$auth->setEntityManager($em);
}
At this point calling $user->getUserGroup()->getName(); should work as intended.

Answer 2

When you store the entity to a session (via Zend_Auth or otherwise), the object is serialized and no longer maintained by Doctrine when subsequently retrieved and unserialized. Try merging the entity back into the EntityManager. See http://www.doctrine-project.org/docs/orm/2.1/en/reference/working-with-objects.html