ZF2 An Invalid Factory Was Registered

I've the following classes and my module config in ZF2 application and it is giving the below error:

While attempting to create applicationformuserform(alias: Application\Form
\UserForm) an invalid factory was registered for this instance type.

UserFormFactory.php

<?php

namespace Application\Factory\Form;

use Zend\ServiceManager\FactoryInterface;
use Zend\ServiceManager\ServiceLocatorInterface;
use Application\Form\UserForm;

class UserFormFactory implements FactoryInterface {

    public function createService(ServiceLocatorInterface $serviceLocator) {
        $services         = $serviceLocator->getServiceLocator();
        $entityManager    = $services->get('Doctrine\ORM\EntityManager');

        $form = new UserForm($entityManager);

        return $form;
    }
}

?>

UserForm.php

<?php

namespace Application\Form;

use Zend\Form\Form;
use Zend\InputFilter\InputFilterProviderInterface;
use Doctrine\ORM\EntityManager;

class UserForm extends Form implements InputFilterProviderInterface {

    protected $entityManager;

    public function __construct(EntityManager $entityManager) {
        parent::__construct();
        $this->entityManager = $entityManager;
    }

    public function init() {
        $this->add(array(
                'name' => 'username',
                'attributes' => array(
                        'type'  => 'text',
                ),
                'options' => array(
                        'label' => 'User Name',
                ),
        ));
        $this->add(array(
                'name' => 'first_name',
                'attributes' => array(
                        'type'  => 'text',
                ),
                'options' => array(
                        'label' => 'First Name',
                ),
        ));
        $this->add(array(
                'name' => 'last_name',
                'attributes' => array(
                        'type'  => 'text',
                ),
                'options' => array(
                        'label' => 'Last Name',
                ),
        ));
        $this->add(array(
                'name' => 'role_id',
                'type' => 'DoctrineModule\Form\Element\ObjectSelect',
                'options' => array(
                        'object_manager'     => $this->entityManager,
                        'target_class'       => 'Application\Entity\Role',
                        'property' => 'id',
                        'is_method' => true,
                        'find_method'        => array(
                                'name'   => 'getRoles',
                        ),
                        'label' => 'User Role',
                ),
        ));
    }

    public function getInputFilterSpecification() {
        return array(); // filter and validation here
    }
}

?>

Module.config.php

'form_elements' => array(
            'factories' => array(
                    'Application\Form\UserForm' => 'Application\Factory\Form\UserFormFactory',
            ),
    ),

And I'm using this form factory in another controller factory

UserControllerFactory.php

<?php

namespace Member\Factory\Controller;

use Zend\ServiceManager\FactoryInterface;
use Zend\ServiceManager\ServiceLocatorInterface;
use Member\Controller\UserController;
use Application\Form\UserForm;

class UserControllerFactory implements FactoryInterface {

    public function createService(ServiceLocatorInterface $serviceLocator) {
        $services    = $serviceLocator->getServiceLocator();
        $userForm    = $services->get('FormElementManager')->get('Application\Form\UserForm');

        $controller  = new UserController($userForm);

        return $controller;
    }
}

?>

Could anybody tell me that what may be the issue?

I got my answer at my own after looking at the code again and again. Actually my Factory and Form folders were outside of src folder that's why Zend could not found all the classes of both folders.

I moved both Factory and Form folder in src and now it's working fine.