Doctrine不会正确加载会话中的关联

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.