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How to use the Symfony error handler to handle exceptions?

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by dedrick , in category: PHP Frameworks , 2 years ago

How to use the Symfony error handler to handle exceptions?

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1 answer

Member

by elise_daugherty , 2 years ago

@dedrick 

Symfony provides a powerful error handling system that allows you to handle exceptions in a clean and organized way. Here's how to use the Symfony error handler to handle exceptions:

  1. Create a new controller method to handle the exception:
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// src/Controller/ErrorController.php

use SymfonyComponentHttpFoundationResponse;
use SymfonyComponentErrorHandlerExceptionFlattenException;

class ErrorController
{
    public function show(FlattenException $exception): Response
    {
        // handle the exception
        // return a response object
    }
}


The show() method takes a FlattenException object as its argument, which represents the flattened version of the original exception. You can handle the exception in this method and return a response object.

  1. Register the controller method as the exception listener in your config/services.yaml file:
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# config/services.yaml

services:
    _defaults:
        autowire: true
        autoconfigure: true

    AppControllerErrorController:
        public: true

    AppEventListenerExceptionListener:
        tags:
            - { name: kernel.event_listener, event: kernel.exception, method: onKernelException }


The ExceptionListener class should be created as a separate listener class that calls the show() method in the ErrorController class.

  1. Implement the onKernelException() method in the ExceptionListener class:
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// src/EventListener/ExceptionListener.php

use SymfonyComponentHttpFoundationResponse;
use SymfonyComponentHttpKernelEventExceptionEvent;
use SymfonyComponentErrorHandlerExceptionFlattenException;

class ExceptionListener
{
    private $controller;

    public function __construct(ErrorController $controller)
    {
        $this->controller = $controller;
    }

    public function onKernelException(ExceptionEvent $event): void
    {
        $exception = $event->getThrowable();
        $flattenException = FlattenException::createFromThrowable($exception);

        $response = $this->controller->show($flattenException);
        $event->setResponse($response);
    }
}


The onKernelException() method is called whenever an exception is thrown in the application. It takes an ExceptionEvent object as its argument, which contains the thrown exception. You can use this exception to create a FlattenException object, call the show() method in the ErrorController, and set the response returned by the show() method as the event response.


That's it! You can now handle exceptions using the Symfony error handler.

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