Zend FR

<?php
/**
 * @ORM\Entity
 */
class User {

    public function getInputFilter()
    {
        if (!$this->inputFilter) {
            $inputFilter = new InputFilter();
            $factory     = new InputFactory();

            $inputFilter->add($factory->createInput(array(
                'name'     => 'username',
                'required' => true,
                'filters'  => array(
                    array('name' => 'StripTags'),
                    array('name' => 'StringTrim'),
                ),
                'validators' => array(
                    array(
                        'name'    => 'DoctrineModule\Validator\NoObjectExists',
                        'options' => array(
                            'object_repository' => ...,
                            'fields'            => array('username'),
                            'messages'          => array(
                                'objectFound' => 'Cet identifiant est déjà utilisé'
                            )
                        )
                    )
                )
            )));

            $this->inputFilter = $inputFilter;
        }

        return $this->inputFilter;
    }
}