Defining form validation constraints in formtypes in symfony

namespace Football\FrontendBundle\Entity;

use DateTime;
use Doctrine\Common\Collections\ArrayCollection;
use Doctrine\Common\Collections\Collection;
use Doctrine\ORM\Mapping as ORM;
use Symfony\Bridge\Doctrine\Validator\Constraints\UniqueEntity;

/**
 * @ORM\Entity(repositoryClass="Football\FrontendBundle\Repository\CountryRepository")
 * @ORM\Table(name="country")
 * @UniqueEntity(fields="code", message="Country code is already taken.")
 * @UniqueEntity(fields="name", message="Country name is already taken.")
 * @ORM\HasLifecycleCallbacks
 */
class Country
{
    /**
     * @ORM\Id
     * @ORM\Column(type="smallint")
     * @ORM\GeneratedValue(strategy="AUTO")
     */
    protected $id;

    /**
     * @ORM\Column(type="string", length=2, unique=true)
     */
    protected $code;

    /**
     * @ORM\Column(name="name", type="string", length=100, unique=true)
     */
    protected $name;
}

namespace Football\FrontendBundle\Form\Type;

use Symfony\Component\Form\AbstractType;
use Symfony\Component\Form\FormBuilderInterface;
use Symfony\Component\OptionsResolver\OptionsResolverInterface;
use Symfony\Component\Validator\Constraints\Length;
use Symfony\Component\Validator\Constraints\NotBlank;
use Symfony\Component\Validator\Constraints\Regex;

class CountryType extends AbstractType
{
    public function buildForm(FormBuilderInterface $builder, array $options = [])
    {
        $builder
            ->setMethod($options['method'])
            ->setAction($options['action'])
            ->add(
                'code',
                'text',
                [
                    'error_bubbling' => true,
                    'constraints' => [
                        new NotBlank(
                            [
                                'message' => 'Country code is required.'
                            ]
                        ),
                        new Regex(
                            [
                                'pattern' => '/^[A-Z]{2}$/',
                                'message' => 'Country code must be exactly 2 character long upper case letters.'
                            ]
                        )
                    ]
                ]
            )
            ->add(
                'name',
                'text',
                [
                    'error_bubbling' => true,
                    'constraints' => [
                        new NotBlank(
                            [
                                'message' => 'Country name is required.'
                            ]
                        ),
                        new Length(
                            [
                                'max' => 100,
                                'maxMessage' => 'Country name cannot be longer than {{ limit }} characters.'
                            ]
                        )
                    ]
                ]
            );
    }

    public function getName()
    {
        return 'country';
    }

    public function setDefaultOptions(OptionsResolverInterface $resolver)
    {
        $resolver->setDefaults(
            ['data_class' => 'Football\FrontendBundle\Entity\Country']
        );
    }
}

{% extends 'FootballFrontendBundle:Country:index.html.twig' %}

{% block body %}
    {% spaceless %}
        {{ parent() }}
        COUNTRY - Create
        <hr />
        {{ form_start(form, { attr: {novalidate: 'novalidate'} }) }}
            {% if form_errors(form) != '' %}

                {{ form_errors(form) }}
            
{% endif %}

            <p>CODE: {{ form_widget(form.code) }}</p>
            <p>NAME: {{ form_widget(form.name) }}</p>

            <p><button name="button">Submit</button></p>
        {{ form_end(form) }}
    {% endspaceless %}
{% endblock %}