Symfony2表单验证总是返回错误:此值不应为空

我在Symfony2中使用表单时遇到了一个奇怪的问题。

首先，我将验证添加为annotations实体类Job：

class Job
{
    /**
     * @ORM'Id
     * @ORM'Column(type="integer")
     * @ORM'GeneratedValue(strategy="AUTO")
     */
    protected $id;
    /**
     * @ORM'Column(type="string", length=255, nullable=true)
     * @Assert'NotBlank()
     * @Assert'Choice(callback="getTypeValues")
     */
    protected $type;
    /**
     * @ORM'Column(type="string", length=255)
     * @Assert'NotBlank()
     */
    protected $company;
    /**
     * @ORM'Column(type="string", length=255, nullable=true)
     */
    protected $logo;
    /**
     * @Assert'Image()
     */
    protected $file;
    /**
     * @ORM'Column(type="string", length=255, nullable=true)
     * @Assert'Url()
     */
    protected $url;
    /**
     * @ORM'Column(type="string", length=255)
     * @Assert'NotBlank()
     */
    protected $position;
    /**
     * @ORM'Column(type="string", length=255)
     * @Assert'NotBlank()
     */
    protected $location;
    /**
     * @ORM'Column(type="text")
     * @Assert'NotBlank()
     */
    protected $description;
    /**
     * @ORM'Column(type="text")
     * @Assert'NotBlank()
     */
    protected $how_to_apply;
    /**
     * @ORM'Column(type="string", length=255, unique=true)
     * @Assert'NotBlank()
     */
    protected $token;
    /**
     * @ORM'Column(type="boolean", nullable=true)
     */
    protected $is_public;
    /**
     * @ORM'Column(type="boolean", nullable=true)
     */
    protected $is_activated;
    /**
     * @ORM'Column(type="string", length=255)
     * @Assert'NotBlank()
     * @Assert'Email()
     */
    protected $email;
    /**
     * @ORM'Column(type="datetime")
     */
    protected $expires_at;
    /**
     * @ORM'Column(type="datetime")
     */
    protected $created_at;
    /**
     * @ORM'Column(type="datetime", nullable=true)
     */
    protected $updated_at;
    /**
     * @ORM'ManyToOne(targetEntity="Category", inversedBy="jobs")
     * @ORM'JoinColumn(name="category_id", referencedColumnName="id")
     * @Assert'NotBlank()
     */
    protected $category;
}

我创建了一个JobType类并在窗体中使用它。所以我可以添加工作。

class JobType extends AbstractType
{
    public function buildForm(FormBuilderInterface $builder, array $options)
    {
        $builder
            ->add('type', 'choice', array('choices' => Job::getTypes(), 'expanded' => true))
            ->add('category')
            ->add('company')
            ->add('file', 'file', array('label' => 'Company logo', 'required' => false))
            ->add('url')
            ->add('position')
            ->add('location')
            ->add('description')
            ->add('how_to_apply', null, array('label' => 'How to apply?'))
            ->add('is_public', null, array('label' => 'Public?'))
            ->add('email')
        ;
    }
    public function setDefaultOptions(OptionsResolverInterface $resolver)
    {
        $resolver->setDefaults(array(
                'data_class' => 'Ibw'JobeetBundle'Entity'Job',
            ));
    }
    public function getName()
    {
        return 'job';
    }
}

这是我的控制器：

public function createAction(Request $request)
{
    $entity = new Job();
    $form = $this->createForm(new JobType(), $entity);
    $form->handleRequest($request);
    if($form->isValid())
    {
        $em = $this->getDoctrine()->getManager();
        $em->persist($entity);
        $em->flush();
        return $this->redirect($this->generateUrl('ibw_job_preview', array(
                'company'   => $entity->getCompanySlug(),
                'location'  => $entity->getLocationSlug(),
                'position'  => $entity->getPositionSlug(),
                'token'     => $entity->getToken(),
            )));
    } else {
        return new Response(var_dump($form->getErrorsAsString()));
//            return new Response($form->getErrorsAsString());
//          return $this->render('IbwJobeetBundle:Job:new.html.twig', array(
//                  'form' => $form->createView(),
//              ));
    }
}

现在当我做var_dump($form->getErrorsAsString())我得到：

string 'ERROR: This value should not be blank.
type:
    0:
        No errors
    1:
        No errors
    2:
        No errors
category:
    No errors
company:
    No errors
file:
    No errors
url:
    No errors
position:
    No errors
location:
    No errors
description:
    No errors
how_to_apply:
    No errors
is_public:
    No errors
email:
    No errors
' (length=355)

或者当我这样做时var_dump($form->getErrors())我得到：

array (size=1)
  0 => 
    object(Symfony'Component'Form'FormError)[614]
      private 'message' => string 'This value should not be blank.' (length=31)
      protected 'messageTemplate' => string 'This value should not be blank.' (length=31)
      protected 'messageParameters' => 
        array (size=0)
          empty
      protected 'messagePluralization' => null

我不知道是什么导致了这个ERROR: This value should not be blank.错误。我很难弄清楚。任何帮助将不胜感激。