1-1 Unidirectional relation Doctrine 2 ORM

use Doctrine\ORM\Mapping as ORM;

/**
 * @ORM\Entity
 * @ORM\Table(name="product")
 */
class Product {
    /**
     * @ORM\Id @ORM\Column(type="integer") @ORM\GeneratedValue
     * @var int
     */
    private $id;

    /**
     * @ORM\OneToOne(targetEntity="Shipment")
     * @ORM\JoinColumn(name="shipment_id", referencedColumnName="id")
     */
    private $shipment;
}

/**
 * @ORM\Entity
 * @ORM\Table(name="shipment")
 */
class Shipment {
    /**
     * @ORM\Id @ORM\Column(type="integer") @ORM\GeneratedValue
     * @var int
     */
    private $id;
}