abstract class HttpExceptionSubscriberBase

Utility base class for exception subscribers.

A subscriber may extend this class and implement getHandledFormats() to indicate which request formats it will respond to. Then implement an on*() method for any error code (HTTP response code) that should be handled. For example, to handle 404 Not Found messages add a method:

public function on404(GetResponseForExceptionEvent $event) {}

That method should then call $event->setResponse() to set the response object for the exception. Alternatively, it may opt not to do so and then other listeners will have the opportunity to handle the exception.

Note: Core provides several important exception listeners by default. In most cases, setting the priority of a contrib listener to the default of 0 will do what you expect and handle the exceptions you'd expect it to handle. If a custom priority is set, be aware of the following core-registered listeners.

• Fast404ExceptionHtmlSubscriber: 200. This subscriber will return a minimalist, high-performance 404 page for HTML requests. It is not recommended to have a priority higher than this one as it will only slow down that use case.
• ExceptionLoggingSubscriber: 50. This subscriber logs all exceptions but does not handle them. Do not register a listener with a higher priority unless you want exceptions to not get logged, which makes debugging more difficult.
• DefaultExceptionSubscriber: -256. The subscriber of last resort, this will provide generic handling for any exception. A listener with a lower priority will never get called.

All other core-provided exception handlers have negative priorities so most module-provided listeners will naturally take precedence over them.

Hierarchy

• class \Drupal\Core\EventSubscriber\HttpExceptionSubscriberBase implements EventSubscriberInterface

File

core/lib/Drupal/Core/EventSubscriber/HttpExceptionSubscriberBase.php, line 47

Namespace

Drupal\Core\EventSubscriber

Members

Name	Modifiers	Type	Description
HttpExceptionSubscriberBase::getHandledFormats	abstract protected	function	Specifies the request formats this subscriber will respond to.
HttpExceptionSubscriberBase::getPriority	protected static	function	Specifies the priority of all listeners in this class.
HttpExceptionSubscriberBase::getSubscribedEvents	public static	function	Registers the methods in this class that should be listeners. Overrides EventSubscriberInterface::getSubscribedEvents
HttpExceptionSubscriberBase::onException	public	function	Handles errors for this subscriber.