你如何在Symfony2中做到这一点？

Question

我有一个名为manageCountriesAction的控制器，我从函数createCountryForm(Countries $entity)生成一个表单，然后我收到Request到createCountryAction函数。

现在是一个棘手的部分，我不知道如何弄清楚，如果表单无效或有任何验证错误，我可以将它们重定向到manageCountriesAction和最后在模板中显示它们（例如：这个字段不能为空）？

这是代码

<?php

namespace CarsProject\BackendBundle\Controller;

use CarsProject\BackendBundle\Entity\Countries;
use CarsProject\BackendBundle\Form\CountriesType;
use Symfony\Bundle\FrameworkBundle\Controller\Controller;
use Symfony\Component\HttpFoundation\Request;

class AdminPanelController extends Controller
{
    /**
     * Locations: manage countries controller
     *
     * @return \Symfony\Component\HttpFoundation\Response
     */
    public function manageCountriesAction()
    {
        $em = $this->getDoctrine()->getEntityManager();
        $countries = $em->getRepository('CarsProjectBackendBundle:Countries')->findAll();

        $newEntity = new Countries();
        $formNewCountry = $this->createCountryForm($newEntity);

        return $this->render('CarsProjectBackendBundle:Backend:manage_countries.html.twig', array(
            'countries_entity' => $countries,
            'form_new_country' => $formNewCountry->createView()
        ));
    }

    /**
     * Create action for Countries Entity
     *
     * @param Request $request
     * @return \Symfony\Component\HttpFoundation\RedirectResponse
     */
    public function createCountryAction(Request $request)
    {
        $entity = new Countries();
        $form = $this->createCountryForm($entity);
        $form->handleRequest($request);

        if ($form->isSubmitted() && $form->isValid()) {
            $em = $this->getDoctrine()->getManager();
            $em->persist($entity);
            $em->flush();
            return $this->redirectToRoute('cars_project_backend_manage_countries');
        }

        /* *
         * If submitted data or $form isn't valid then redirect the response (form validation errors)
         * to "manageCountriesAction" controller and finally make the validation errors appear
         * in the twig template of "manageCountriesAction" controller.
         **/

    }

    /**
     * Create form for Countries Entity
     *
     * @param Countries $entity
     * @return \Symfony\Component\Form\Form
     */
    public function createCountryForm(Countries $entity)
    {
        $form = $this->createForm(new CountriesType(), $entity, array(
            'action' => $this->generateUrl('cars_project_backend_manage_countries_form_new'),
            'method' => 'POST'
        ));

        return $form;
    }
}