Using Symfony forms without a database entity

I've been developing an application based on Symfony 3, and part of that application involves an import process where a user can upload csv files. One thing that I've never been too sure about with symfony is using the forms component without a database entity to attach it too. In the past I've typically just used an array to hold the form data, but this always felt improper. This time I decided to try building an entity class to base the form on, even though it has no mapping to anything in the database.

This is the entity I created. In addition to defining the fields for the form I also setup validation to ensure at least one of the fields has been populated.

class StudentImportFiles {
/** @var File */
private $studentList; /** @var File */ private$transferList;
/** @var File */
private $enrollmentList; public static function loadValidatorMetadata(ClassMetadata$metadata){
$metadata->addConstraint(new Callback(function(self$self, ExecutionContextInterface $context){ if (!($self->studentList || $self->transferList ||$self->enrollmentList)){
$context->addViolation('At least one import file must be selected'); } })); } public function getStudentList(){ return$this->studentList;
}

public function setStudentList($studentList){$this->studentList = $studentList; return$this;
}

public function getTransferList(){
return $this->transferList; } public function setTransferList($transferList){
$this->transferList =$transferList;

return $this; } public function getEnrollmentList(){ return$this->enrollmentList;
}

public function setEnrollmentList($enrollmentList){$this->enrollmentList = $enrollmentList; return$this;
}
}


This is the form type I created. It simply maps to the above entity and ensures it is valid.

class StudentImportFilesType extends AbstractType {
public function buildForm(FormBuilderInterface $builder, array$options){
$builder ->add('studentList', FileType::class, [ 'required' => false ]) ->add('transferList', FileType::class, [ 'required' => false ]) ->add('enrollmentList', FileType::class, [ 'required' => false ]) ; } public function configureOptions(OptionsResolver$resolver){
\$resolver->setDefaults([
'data_class' => StudentImportFiles::class
, 'constraints' => [
new Valid()
]
]);
}
}


Is this proper usage of the forms component for such a scenario? Are there any improvements that could be made?