YML validation file is ignored

Question

I am new to the Symfony 2 web framework, and am struggling with a very basic validation task. I have an entity model Post that has a member slug, which I use to build the link to the post. In Post.orm.yml I defined unique: true and want to include this constraint as a validator as well.

I have created a file validation.yml:

# src/OwnBundles/BlogpostBundle/Resources/config/validation.yml

OwnBundles\BlogpostBundle\Entity\Post:
    properties:
        slug:
            - NotBlank: ~
    constraints:
        - Symfony\Bridge\Doctrine\Validator\Constraints\UniqueEntity: slug

The creation function in my controller is quite simple:

public function addAction(Request $request)
{
    $post = new Post();
    $form = $this->createForm(new PostType(), $post);

    if($request->getMethod() == 'POST')
    {
        $form->bind($request);
        if($form->isValid())
        {
            $em = $this->getDoctrine()->getManager();
            $em->persist($post);
            $em->flush();
            return $this->redirect(
                $this->generateUrl('own_bundles_blogpost_homepage')
            );
        }
    }
    return $this->render(
        'OwnBundlesBlogpostBundle:Default:add.html.twig',
        array(
            'title' => 'Add new blogpost',
            'form' => $form->createView(),
        )
    );
}

The basic pageflow works fine, I can add posts and see them, but if I duplicate a post title to test my validation, it throws an exception: SQLSTATE[23000]: Integrity constraint violation: 1062 Duplicate entry 'duplicate-slug' for key 'UNIQ_FAB8C3B3989D9B62'. I have been scanning through documentation for quite some time now, but I was not able to find out why my $form->isValid() returns true.

Solution

Did you enable validation in app/config/config.yml ?

...

framework:
    ...
    validation:    { enabled: true }
    ...

...

and if you want to define validation with annotations too, you have to both enable validation and annotation validation :

...

framework:
    ...
    validation:    { enabled: true, enable_annotations: true }
    ...

...

And then don't forget clear the app/cache directory.