Error Handling

In the same way that a resource representation can be exchanged between client and server without any knowledge of the underlying data structure, so can error documents.

Drest comes shipped with a number of error response documents. Which document is used will be determined by a client’s Accept header when they make a request.

All representation classes will have a corresponding error response document. So if a client performed a [GET] request to an unavailable resource with an Allow: application/json HTTP header, they’re likely to receive a Drest\Error\Response\Json document that’ll produce something like:

HTTP/1.1 404 Not Found
Content-Type: application/json

  "message": "No resource available"

If your users are using the drest client tool then they can catch an exception and get a hook onto the error document that was created on the server. They can also get hold of a Drest\Client\Response instance.

$user = ...user object creation..;
    $response = $client->post('/users', $user);
} catch (\Drest\Error\ErrorException $e)
    // Echo the error message: "Server Error"
    echo $e->getErrorDocument()->getMessage();
    // Echo the full error document: {"message": "Server Error"}
    echo $e->getErrorDocument()->render();
    // Get a hook on the Drest\Response object
    $response = $e->getResponse();
    switch ($response->getStatusCode())
       ....Do something based on the status code

For more information on how this work go to the client tool section.

If the server is in debug mode then no error document is created and the thrown exception will bubble up. See advanced configuration for more details.

Hander Class

The error handler object is responsible for interpreting an error (exception) and deciding how to handle a response for it. It’s job is to determine a suitable error message, and an HTTP status code to return back to the client.

A number of different exception types are passed into this object (including Doctrine ORM/DBAL, SQL Exceptions).

These documents can then be easily converted back into it’s error document form on the client side.

Default handler

By default drest will use an instance of Drest\Error\Handler\DefaultHandler to handle errors. An example of a few of its behaviours are:

case 'Doctrine\ORM\NonUniqueResultException':
        $this->response_code = Response::STATUS_CODE_300;
        $error_message = 'Multiple resources available';
    case 'Doctrine\ORM\NoResultException':
        $this->response_code = Response::STATUS_CODE_404;
        $error_message = 'No resource available';

Of course these can all be overridden by creating and registering your own error handler.

Create your own handler

To customise error messages and to be able to determine which HTTP statuses messages to use; based on the exception thrown you must create and register you own error handler.

This class must extend Drest\Error\Handler\AbstractHandler and implement an error method with the following signature:

public function error(\Exception $e, $defaultResponseCode = 500, ResponseInterface &$errorDocument)

The exception is passed into the error call with a; - $defaultResponseCode - This is an http status code that’s been “suggested” from the service action. - &$errorDocument - The error document object to be populated with an error message.

Once this is created you must instantiate it and pass it into the drest manager before the dispatch() method is called.

// ..creation of the drest manager
$error_handler = new My\Error\Handler();

All errors will now be passed through your custom error handler. Currently you can only have one error handler registered.