如何在symfony 2中捕获异常？

您应该注意可能引发的异常:

public function postAction(Request $request)
{
  // ...

  try{
    $em = $this->getDoctrine()->getManager();
    $em->persist($entity);
    $em->flush();

    return $this->redirect($this->generateUrl('target page'));

  } catch(\Doctrine\ORM\ORMException $e){
    // flash msg
    $this->get('session')->getFlashBag()->add('error', 'Your custom message');
    // or some shortcut that need to be implemented
    // $this->addFlash('error', 'Custom message');

    // error logging - need customization
    $this->get('logger')->error($e->getMessage());
    //$this->get('logger')->error($e->getTraceAsString());
    // or some shortcut that need to be implemented
    // $this->logError($e);

    // some redirection e. g. to referer
    return $this->redirect($request->headers->get('referer'));
  } catch(\Exception $e){
    // other exceptions
    // flash
    // logger
    // redirection
  }

  return $this->render('MyTestBundle:Article:new.html.twig', array(
    'entity' => $entity,
    'form'   => $form->createView(),
  ));
}