4-exception-controller-support.rst

Step 4: ExceptionController support

When implementing an API it is also necessary to handle exceptions in a RESTful way, while ensuring that no security sensitive information leaks out. This bundle provides an extra controller for that job. Using this custom ExceptionController it is possible to leverage the View layer when building responses for uncaught Exceptions.

The ExceptionController can be enabled via the FOSRestBundle configuration:

fos_rest:
    exception:
        enabled: true
        exception_controller: 'Acme\DemoBundle\Controller\ExceptionController::showAction'

Note

The FOSRestBundle ExceptionController is executed before the one of the TwigBundle.

To map Exception classes to HTTP response status codes an exception map may be configured, where the keys match a fully qualified class name and the values are either an integer HTTP response status code or a string matching a class constant of the Symfony\Component\HttpFoundation\Response class:

fos_rest:
    exception:
        codes:
            'Symfony\Component\Routing\Exception\ResourceNotFoundException': 404
            'Doctrine\ORM\OptimisticLockException': HTTP_CONFLICT
        messages:
            'Acme\HelloBundle\Exception\MyExceptionWithASafeMessage': true

If you want to display the message from the exception in the content of the response, add the exception to the messages map as well. If not only the status code will be returned.

If you know what status code you want to return you do not have to add a mapping, you can do this in your controller:

<?php

namespace AppBundle\Controller;

use Symfony\Component\HttpKernel\Exception\HttpException;

class UsersController extends Controller
{
    public function postUserCommentsAction($slug)
    {
        if (!$this->validate($slug)) {
            throw new HttpException(400, "New comment is not valid.");
        }
    }
}

In order to make the serialization format of exceptions customizable it is possible to use serializer normalizers.

See how to create handlers for the JMS serializer and how to create normalizers for the Symfony serializer.

That was it!

Note

If you are receiving a 500 error where you would expect a different response, the issue is likely caused by an exception inside the ExceptionController. For example a template is not found or the serializer failed. You should take a look at the logs of your app to see if an uncaught exception has been logged.