Symfony2 - Doctrine保存具有一对一关系的实体

我想保存我已经创建的表单，但我有一个错误。

我有三个实体

class T {
    /**
     * @ORM'OneToOne(targetEntity="MyNameSpace'ProfileBundle'Entity'Person", cascade={"persist"})
     */
    private $information;
}
class Person {
    /**
     * @ORM'OneToOne(targetEntity="MyNameSpace'MediaBundle'Entity'Document", cascade={"persist"}))
     */
    private $photo_profile;
}
class Document
{
    private $file;
}

当我用下面的代码保存我的"T"类时:

public function createAction()
{
        $entity     = new T();                        
        $request = $this->getRequest();
        $form    = $this->createForm(new TType(), $entity);        
        $form->bindRequest($request);
        if ($form->isValid()) 
        {
            $em = $this->getDoctrine()->getEntityManager();
            $em->persist($entity);            
            $em->flush();
        }
} 

我有这个错误:

SQLSTATE[23000]: Integrity constraint violation: 1452不能添加或更新子行:a foreign key constraint fails (namespace . c .)person，约束FK_3370D440809EFCB0外键(photo_profile_id)引用Document (id))

任何帮助都会很酷

谢谢大家

---

下面是我的代码:

/**
 * Creates a new Tutor entity.
 */
public function createAction()
{       
    $entity  = new T();        
    $person = new Person();        
    $document = new Document();
    $person->setPhoto($document);
    $entity->setInformation($person);
    $request = $this->getRequest();
    $form    = $this->createForm(new TType(), $entity);        
    $form->bindRequest($request);
    if ($form->isValid()) {
        $em = $this->getDoctrine()->getEntityManager();
        $em->persist($entity->getInformation()->getPhoto());
        $em->persist($entity->getInformation());           
        $em->flush();
        $em->persist($entity);
        $em->flush();                       
        return $this->redirect($this->generateUrl('Index'));
    }

和我有这个错误:

SQLSTATE[23000]: Integrity constraint violation: 1452不能添加或更新子行:a foreign key constraint fails (db . 0)。T，约束FK_58C6694C2EF03101外键(information_id)引用Person (id)

任何帮助都将是很酷的

谢谢