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API Connections

The Connection is a very simple wrapper around the HttpClientInterface. It links the client to the ApiRouter and provides default implementations for all the main HTTP verbs. This can be overridden to use other HTTP clients (e.g. Guzzle) or mocked out entirely (see tests for an example).

Note: if implementing another HTTP client, the responses are expected to be Symfony client responses. You would need to translate e.g. a Guzzle response to the symfony response to keep the interface valid.

The exposed methods allow for a named route and route parameters and/or a body payload. The optional parameters offered by the Symfony client are deliberately not exposed. If you require an auth-bearer or token authorisation, then implement a custom client that will handle these requirements.

Alternatively: attach an event listener to the PreRequestEvent and modify the headers or body payload as needed before the request is dispatched.

<?php
use Somnambulist\Components\ApiClient\Client\Connection;
use Somnambulist\Components\ApiClient\Client\ApiRouter;
use Symfony\Component\HttpClient\HttpClient;

$conn = new Connection(HttpClient::create(), new ApiRouter());

In the same way that the ApiRouter can be extended, the ApiClient can be extended to provide additional functionality. The base of this library is more focused on offering read defaults for APIs than complex push requests.

The preferred method of extending is by decorating the connection object. Several decorators are included along with a AbstractDecorator base class.

Connection Events

From 2.0.0 the Connection object makes use of the Symfony EventDispatcher and will fire:

  • PreRequestEvent
  • PostRequestEvent

The PreRequestEvent receives:

  • the named route of the request
  • route parameters
  • body parameters

Headers may be added via the PreRequestEvent (e.g.: Request-ID), or the body / route modified as needed (e.g.: to handle BC API calls transparently or tag the current user etc).

The PostRequestEvent receives:

  • HttpClient Response object
  • the original route, parameters, body and headers

Custom Header Injection

There is an included header injector event subscriber / listener that can be added to the standard Symfony services.yaml or the event dispatcher. This can inject from the main RequestStack, a request header (configurable) for tracking requests across service calls.

For example: in a micro-services setup, you may use the X-Request-Id header to track a single user journey through the stack. An injector can be configured to pull the header from the apps request object and apply it to all ApiClient calls.

Additional listeners may be created and added to the event to trigger other logic or append additional information such as the current user or additional contextual data.