ZF Api Problem

Introduction

This module provides data structures and rendering for the API-Problem format.

• Problem Details for HTTP APIs, used for reporting API problems.

Requirements

Please see the composer.json file.

Installation

Run the following composer command:

$ composer require "zfcampus/zf-api-problem:~1.0-dev"

Alternately, manually add the following to your composer.json, in the require section:

"require": {
    "zfcampus/zf-api-problem": "~1.0-dev"
}

And then run composer update to ensure the module is installed.

Finally, add the module name to your project's config/application.config.php under the modules key:

return array(
    /* ... */
    'modules' => array(
        /* ... */
        'ZF\ApiProblem',
    ),
    /* ... */
);

Configuration

User Configuration

The top-level configuration key for user configuration of this module is zf-api-problem.

Key: accept_filters

An array of Accept header media types that, when matched, will result in the ApiProblemListener handling an MvcEvent::EVENT_RENDER_ERROR event.

Key: render_error_controllers

An array of controller service names that, if matched as the controller parameter in the MVC RouteMatch, will cause the ApiProblemListener to handle MvcEvent::EVENT_RENDER_ERROR events.

System Configuration

The following configuration is provided in config/module.config.php to enable the module to function:

'service_manager' => array(
    'aliases'   => array(
        'ZF\ApiProblem\ApiProblemListener'  => 'ZF\ApiProblem\Listener\ApiProblemListener',
        'ZF\ApiProblem\RenderErrorListener' => 'ZF\ApiProblem\Listener\RenderErrorListener',
        'ZF\ApiProblem\ApiProblemRenderer'  => 'ZF\ApiProblem\View\ApiProblemRenderer',
        'ZF\ApiProblem\ApiProblemStrategy'  => 'ZF\ApiProblem\View\ApiProblemStrategy',
    ),
    'factories' => array(
        'ZF\ApiProblem\Listener\ApiProblemListener'             => 'ZF\ApiProblem\Factory\ApiProblemListenerFactory',
        'ZF\ApiProblem\Listener\RenderErrorListener'            => 'ZF\ApiProblem\Factory\RenderErrorListenerFactory',
        'ZF\ApiProblem\Listener\SendApiProblemResponseListener' => 'ZF\ApiProblem\Factory\SendApiProblemResponseListenerFactory',
        'ZF\ApiProblem\View\ApiProblemRenderer'                 => 'ZF\ApiProblem\Factory\ApiProblemRendererFactory',
        'ZF\ApiProblem\View\ApiProblemStrategy'                 => 'ZF\ApiProblem\Factory\ApiProblemStrategyFactory',
    ),
),
'view_manager' => array(
    // Enable this in your application configuration in order to get full
    // exception stack traces in your API-Problem responses.
    'display_exceptions' => false,
),

ZF2 Events

Listeners

ZF\ApiProblem\Listener\ApiProblemListener

The ApiProblemListener attaches to three events in the MVC lifecycle:

• MvcEvent::EVENT_DISPATCH as a shared listener on Zend\Stdlib\DispatchableInterface with a priority of 100.
• MvcEvent::EVENT_DISPATCH_ERROR with a priority of 100.
• MvcEvent::EVENT_RENDER with a priority of 1000.

If the current Accept media type does not match the configured API-Problem media types (by default, these are application/json and application/*+json), then this listener returns without taking any action.

When this listener does take action, the purposes are threefold:

• Before dispatching, the render_error_controllers configuration value is consulted to determine if the ZF\ApiProblem\Listener\RenderErrorListener should be attached; see RenderErrorListener for more information.
• After dispatching, detects the type of response from the controller; if it is already an ApiProblem model, it continues without doing anything. If an exception was thrown during dispatch, it converts the response to an API-Problem response with some information from the exception.
• If a dispatch error occurred, and the Accept type is in the set defined for API-Problems, it attempts to cast the dispatch exception into an API-Problem response.

ZF\ApiProblem\Listener\RenderErrorListener

This listener is attached to MvcEvent::EVENT_RENDER_ERROR at priority 100. This listener is conditionally attached by ZF\ApiProblem\Listener\ApiProblemListener for controllers that require API Problem responses. With a priority of 100, this ensures that this listener runs before the default ZF2 listener on this event. In cases when it does run, it will cast an exception into an API-problem response.

ZF\ApiProblem\Listener\SendApiProblemResponseListener

This listener is attached to SendResponseEvent::EVENT_SEND_RESPONSE at priority -500. The primary purpose of this listener is, on detection of an API-Problem response, to send appropriate headers and the problem details as the content body. If the view_manager's display_exceptions setting is enabled, the listener will determine if the API-Problem represents an application exception, and, if so, inject the exception trace as part of the serialized response.

ZF2 Services

Event Services

• ZF\ApiProblem\Listener\ApiProblemListener
• ZF\ApiProblem\Listener\RenderErrorListener
• ZF\ApiProblem\Listener\SendApiProblemResponseListener

View Services

ZF\ApiProblem\View\ApiProblemRenderer

This service extends the JsonRenderer service from the ZF2 MVC layer. Its primary responsibility is to decorate JSON rendering with the ability to optionally output stack traces.

ZF\ApiProblem\View\ApiProblemStrategy

This service is a view strategy that detects a ZF\ApiProblem\View\ApiProblemModel; when detected, it selects the ApiProblemRender, and injects the response with a Content-Type header that contains the application/problem+json media type. This is similar in nature to Zend Framework 2's JsonStrategy.

Models

ZF\ApiProblem\ApiProblem

An instance of ZF\ApiProblem\ApiProblem serves the purpose of modeling the kind of problem that is encountered. An instance of ApiProblem is typically wrapped in an ApiProblemResponse. Most information can be passed into the constructor:

class ApiProblem {
    public function __construct(
        $status,
        $detail,
        $type = null,
        $title = null,
        array $additional = array()
    ) {
        /* ... */
    }
}

For example:

new ApiProblem(404, 'Entity not found');

// or

new ApiProblem(424, $exceptionInstance);

ZF\ApiProblem\ApiProblemResponse

An instance of ZF\ApiProblem\ApiProblemResponse can be returned from any controller service or ZF2 MVC event in order to short-circuit the MVC lifecycle and immediately return a response. When it is, the response will be converted to the proper JSON structure for an API-Problem, and the Content-Type header will be set to the application/problem+json media type.

For example:

use Zend\Mvc\Controller\AbstractActionController;
use ZF\ApiProblem\ApiProblem;
use ZF\ApiProblem\ApiProblemResponse;

class MyController extends AbstractActionController
{
    /* ... */
    public function fetch($id)
    {
        $entity = $this->model->fetch($id);
        if (! $entity) {
            return new ApiProblemResponse(new ApiProblem(404, 'Entity not found'));
        }
        return $entity;
    }
}