Symfony2 setNormalizer with defined options - php

Question

I'm having a problem with Symfony options resolver where I need to specify a list of defined variables that should be normalized.
The problem is: I don't want to define all these variables again in
$resolver->setDefined();
because I have a list of defined fields in $builder and the same fields are defined in the entity SlotRequest.
Is there a different way of assigning all fields/variables from entity to resolver?
First approach:
$resolver->setDefined([
'date_form','etc..' ]);
But, it pointless because in the real world I have to normalize 10+ variables + 20 fields)
Second approach would be to parse all annotations from the entity 'SlotRequest', and then fill up an array with that object.
$resolver->setDefined($anArrayOfParsedFieldsFromEntity);
Is there a better way of doing this?
An example of using:
In controller:
$form = $this->createForm(new SlotRequestType(), new SlotRequest());
SlotRequestType:
class SlotRequestType extends AbstractType
{
/**
* #var CCriteria
*/
protected $resolved = null;
/**
* #param FormBuilderInterface $builder
* #param array $options
*/
public function buildForm(FormBuilderInterface $builder, array $options)
{
$builder
->add('date_from',null,['property_path'=>'dateFrom']);
//more fields
}
/**
* #param OptionsResolver $resolver
*/
public function configureOptions(OptionsResolver $resolver)
{
$this->resolved = new \CCriteria();
$resolver->setDefaults(array(
'data_class' => SlotRequest::class,
'allow_extra_fields' => true,
'method' => 'GET'
));
$resolver->setDefined([....]);// the list of fields
$resolver->setNormalizer('date_from', function (Options $options, $value) {
$dateFrom = new \DateTime($value);
$this->resolved->setStartDate($dateFrom->getTimestamp());
return $value;
});
//more normalizers
}
/**
* #return null
*/
public function getName()
{
return null;
}
/**
* #return CCriteria
*/
public function getResolved()
{
return $this->resolved;
}
Entity SlotRequest
<?php
namespace Test/Entity;
class SlotRequest
{
/**
* #var string
* #Assert\NotBlank(message="Parameter [date_from] is missing.")
* #Assert\Type(
* type="string",
* message="The value {{ value }} is not a valid {{ type }}."
* )
* #Assert\Date()
*/
public $dateFrom;
//more fields
}