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Example of handling exceptions with listeners #5503

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Example of handling exceptions with listeners
mdburgos Jul 8, 2015
ddeaa7a
Update error_pages.rst
mdburgos Jul 9, 2015
b77a161
Removed acme prefix and reworded sentences
mdburgos Mar 31, 2016
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121 changes: 121 additions & 0 deletions cookbook/controller/error_pages.rst
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Expand Up @@ -250,6 +250,127 @@ This approach allows you to create centralized and layered error handling:
instead of catching (and handling) the same exceptions in various controllers
time and again, you can have just one (or several) listeners deal with them.

A centralized error handling that also allows to log exceptions might look like this::

// src/AppBundle/EventListener/ExceptionListener.php
namespace AppBundle\EventListener;

use Psr\Log\LoggerInterface;
use Symfony\Component\HttpFoundation\Response;
use Symfony\Component\HttpKernel\Event\GetResponseForExceptionEvent;
use Symfony\Component\HttpKernel\Exception\HttpExceptionInterface;

class ExceptionListener
{
private $logger;

public function __construct(LoggerInterface $logger)
{
$this->logger = $logger;
}

public function onKernelException(GetResponseForExceptionEvent $event)
{
// Get the exception object from the received event
$exception = $event->getException();
$message = sprintf(
'Error: %s. Code: %s',
$exception->getMessage(),
$exception->getCode()
);

// Log the exception to the configured log file (i.e. app.log)
$this->logger->error($message);

// Customize the response object to display the exception details
$response = new Response();
$response->setContent($message);

// HttpExceptionInterface is a special type of exception that
// holds status code and header details
if ($exception instanceof HttpExceptionInterface) {
$response->setStatusCode($exception->getStatusCode());
$response->headers->replace($exception->getHeaders());
} else {
$response->setStatusCode(Response::HTTP_INTERNAL_SERVER_ERROR);
}

// Send the modified response object to the event
$event->setResponse($response);
}
}

Now, you need to register your listener:

.. configuration-block::

.. code-block:: yaml

# app/config/services.yml
services:
app.exception_listener:
class: AppBundle\EventListener\ExceptionListener
arguments: ["@logger"]
tags:
- { name: kernel.event_listener, event: kernel.exception, method: onKernelException }

.. code-block:: xml

<!-- app/config/services.xml -->
<service id="app.exception_listener" class="AppBundle\EventListener\ExceptionListener">
<argument type="service" id="logger" />
<tag name="kernel.event_listener" event="kernel.exception" method="onKernelException" />
</service>

.. code-block:: php

// app/config/services.php
$container
->register('app.exception_listener', 'AppBundle\EventListener\ExceptionListener')
->addArgument(new Reference('logger'))
->addTag('kernel.event_listener', array('event' => 'kernel.exception', 'method' => 'onKernelException'))
;

Finally, you need to add a new handler that will log the exceptions to the configured log file (app.log):

.. configuration-block::

.. code-block:: yaml

# app/config/config.yml
monolog:
handlers:
applog:
type: stream
path: /path/to/app.log
level: error

.. code-block:: xml

<!-- app/config/config.xml -->
<monolog:config>
<monolog:handler
name="applog"
type="stream"
path="/path/to/app.log"
level="error"
/>
</monolog:config>
</container>

.. code-block:: php

// app/config/config.php
$container->loadFromExtension('monolog', array(
'handlers' => array(
'applog' => array(
'type' => 'stream',
'path' => '/path/to/app.log',
'level' => 'error',
),
),
));

.. tip::

See :class:`Symfony\\Component\\Security\\Http\\Firewall\\ExceptionListener`
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