Doctrine 2 @ManyToOne attribute always return null

I have these entities

/** @ORM\Entity */ class Produto { /* Other attributes */ /** * @ORM\ManyToOne(targetEntity="Produto\Entity\Categoria") * @ORM\JoinColumn(name="categoria_id", referencedColumnName="id") */ private $categoria; public function getCategoria() { return $this->categoria; } public function setCategoria(Categoria $categoria) { $this->categoria = $categoria; } } 

and

/** @ORM\Entity */ class Categoria { /* Other attributes */ /** @ORM\Column(type="string") */ private $nome; } 

but when I call the method findAll the $categoria attribute category is always null, what am I doing wrong?

I tried adding the OneToMany annotation on the entity categoria, but it did not work well, there is somewhere that explains why this happens? I found nothing in the documentation