Symfony2, Keep form data across redirect - forms

Question

How to use session for retrieving data during redirect? I am getting the error message: "exception 'Symfony\Component\Form\Exception\AlreadySubmittedException' with message 'You cannot change the data of a submitted form."
C:\Bitnami\wampstack-5.5.30-0\sym_prog\proj3_27\src\MeetingBundle\Controller\UserController.php
/**
* Creates a new User entity.
*
* #Route("/new", name="user_new")
* #Method({"GET", "POST"})
*/
public function newAction(Request $request)
{
$user = new User();
$form = $this->createForm(new UserType(), $user);
$form->handleRequest($request);
$session = $this->getRequest()->getSession();
$form->setData(unserialize($session->get('userFilter')));
if ( $form->isSubmitted() && $form->isValid() ) {
$session->set( 'userFilter', serialize($form->getData()) );
$em = $this->getDoctrine()->getManager();
$em->persist($user);
$em->flush();
return $this->redirectToRoute('user_edit', array('id' => $user->getId()));
}
return $this->render('MeetingBundle::user/new.html.twig', array(
'user' => $user,
'form' => $form->createView(),
));
} // public function newAction(Request $request)
C:\Bitnami\wampstack-5.5.30-0\sym_prog\proj3_27\src\MeetingBundle\EventListener\ExceptionListener.php
<?php
namespace MeetingBundle\EventListener;
use Symfony\Component\HttpKernel\Event\GetResponseForExceptionEvent;
use Symfony\Component\HttpFoundation\Response;
use Symfony\Component\HttpFoundation\RedirectResponse;
use Symfony\Component\HttpFoundation\Request;
use Symfony\Component\Routing\Router;
use Symfony\Component\HttpKernel\Exception\HttpExceptionInterface;
use Symfony\Bundle\FrameworkBundle\Templating\EngineInterface;
//every time the Kernel throws the kernel.exception event, the function onKernelException() is called.
/* also must create service :
meeting.exception_listener:
class: MeetingBundle\EventListener\ExceptionListener
arguments: [#templating, #kernel, #router]
tags:
- { name: kernel.event_listener, event: kernel.exception, method: onKernelException }
*/
class ExceptionListener
{
protected $templating;
protected $kernel;
protected $router;
public function __construct( EngineInterface $templating, $kernel, Router $router)
{
$this->templating = $templating;
$this->kernel = $kernel;
$this->router = $router;
}
public function onKernelException(GetResponseForExceptionEvent $event)
{
$exception = $event->getException();
$request=$event->getRequest();
$referer = $event->getRequest()->headers->get('referer');
$msg="";
$excStr=$exception->__toString(); // returns string finally!
$bdup=strpos( $excStr , 'Integrity constraint violation: 1062 Duplicate entry' );
if($bdup) {
$msg=" This username is already taken. Choose another username. ";
}
if(strlen($msg)!=0) {
// flash messsages are displayed in layout.html
$request->getSession()
->getFlashBag()
->add('Error', $msg);
}
$response = new RedirectResponse($referer); // redirect to the error page
if ($exception instanceof HttpExceptionInterface) {
$response->setStatusCode($exception->getStatusCode());
$response->headers->replace($exception->getHeaders());
} else {
$response->setStatusCode(Response::HTTP_INTERNAL_SERVER_ERROR);
}
$event->setResponse($response);
}
}