Call to a member function getRepository() on a non-object - mongodb

Question

I am new In symfony2 with mongoDB, I am creating one relationship with document relation using ODM. I facing above issue when I creating form type, My file code as below
File path: /src/AppBundle/Form/Type/ProductFormType.php
<?php
namespace AppBundle\Form\Type;
use Symfony\Component\Form\AbstractType;
use Symfony\Component\Form\FormBuilderInterface;
use Symfony\Component\OptionsResolver\OptionsResolverInterface;
class ProductFormType extends AbstractType
{
public function buildForm(FormBuilderInterface $builder, array $options)
{
$builder->add('name', 'text', array('label' => 'Product Name'))
->add('description', 'textarea',array('label' => 'Description'))
->add('Category', 'document', array(
'label'=>'Product Category',
'class' => 'AppBundle:Category',
'property' => 'name',
))
->add('save', 'submit');
}
public function getName()
{
return 'product';
}
public function setDefaultOptions(OptionsResolverInterface $resolver)
{
$resolver->setDefaults(array(
'data_class' => 'AppBundle\Document\Product'
));
}
}
?>
File: src/AppBundle/Document/product.php
<?php
namespace AppBundle\Document;
use Doctrine\ODM\MongoDB\Mapping\Annotations as ODM;
use Symfony\Component\Validator\Constraints as Assert;
/** #ODM\Document */
class Product
{
/** #ODM\Id */
private $id;
/** #ODM\String */
protected $name;
/** #ODM\String */
protected $description;
/** #ODM\ReferenceOne(targetDocument="Category", cascade="all") */
private $Category;
public function getId() { return $this->id; }
public function getName() { return $this->name; }
public function setName($name) { $this->name = $name; }
/**
* Set category
*
* #param AppBundle\Document\Category $category
* #return self
*/
public function setCategory(\AppBundle\Document\Category $category)
{
$this->Category = $category;
return $this;
}
/**
* Get category
*
* #return AppBundle\Document\Category $category
*/
public function getCategory()
{
return $this->Category;
}
public function getDescription() { return $this->description; }
public function setDescription($description) { $this->description = $description; }
}
File src/Appbundle/Docment/Category.php
<?php
namespace AppBundle\Document;
use Doctrine\ODM\MongoDB\Mapping\Annotations as ODM;
use Symfony\Component\Validator\Constraints as Assert;
use Doctrine\Common\Collections\ArrayCollection;
//** #ODM\Document */
class Category
{
/** #ODM\Id */
protected $id;
/** #ODM\String */
protected $cat_id;
/** #ODM\String */
protected $categoryname;
/** #ReferenceMany(targetDocument="Product" mappedBy="category") */
private $products;
public function __construct()
{
$this->products = new ArrayCollection();
}
/**
* Add product
*
* #param \AppBundle\Document\Product $product
*
* #return Category
*/
public function addProduct(\AppBundle\Document\Product $product)
{
$this->products[] = $product;
return $this;
}
/**
* Remove product
*
* #param \AppBundle\Document\Product $product
*/
public function removeProduct(\AppBundle\Document\Product $product)
{
$this->products->removeElement($product);
}
/**
* Get products
*
* #return \Doctrine\Common\Collections\Collection
*/
public function getProducts()
{
return $this->products;
}
public function getId()
{
return $this->id;
}
public function getCat_id() { return $this->cat_id; }
public function setCat_id($cat_id) { $this->cat_id = $cat_id; }
public function getDescription() { return $this->categoryname; }
public function setDescription($categoryname) { $this->categoryname = $categoryname; }
}
I also tried Following process :
getter-setter for MongoDB
php app/console doctrine:mongodb:generate:documents AppBundle
Then clear cache and set developer enviroment
can anybody have a solutions, Please help me.
Thanks in Advance