PhlyRestfully: ZF2 Module for JSON REST Services

This module provides structure and code for quickly implementing RESTful APIs that use JSON as a transport.

It allows you to create RESTful JSON APIs that use the following standards:

• HAL, used for creating hypermedia links
• Problem API, used for reporting API problems

Resources

A generic Resource class is provided, which provides the following operations:

• create($data)
• update($id, $data)
• replaceList($data)
• patch($id, $data)
• delete($id)
• deleteList($data = null)
• fetch($id)
• fetchAll()

Each method:

• Ensures the incoming arguments are well-formed (primarily that $data is an array or object)
• Triggers an event with the incoming data
• Pulls the last event listener result, and ensures it is well-formed for the operation (typically, returns an array or object; in the case of delete and deleteList, looks for a boolean; in the case of fetchAll, looks for an array or Traversable)

As such, your job is primarily to create a ListenerAggregate for the Resource which performs the actual persistence operations.

Controller

A generic ResourceController is provided which intercepts incoming requests and passes data to the Resource. It then inspects the result to generate an appropriate response.

In cases of errors, a Problem API response payload is generated.

When a resource or collection is returned, a HAL payload is generated with appropriate links.

In all cases, appropriate HTTP response status codes are generated.

The controller expects you to inject the following:

• Resource
• Route name that resolves to the resource
• Event identifier for allowing attachment via the shared event manager; this is passed via the constructor (optional; by default, listens to PhlyRestfully\ResourceController)
• "Accept" criteria for use with the AcceptableViewModelSelector (optional; by default, assigns any */json requests to the RestfulJsonModel)
• HTTP OPTIONS the service is allowed to respond to, for both collections and individual resources (optional; head and options are always allowed; by default, allows get and post requests on collections, and delete, get, patch, and put requests on resources)
• Page size (optional; for paginated results. Defaults to 30.)

Tying it Together

You will need to create at least one factory, and potentially several.

Absolutely required is a unique controller factory for the ResourceController. As noted in the previous section, you will have to inject several dependencies. These may be hard-coded in your factory, or pulled as, or from, other services.

As a quick example:

'PasteController' => function ($controllers) {
    $services   = $controllers->getServiceLocator();
    $events     = $services->get('EventManager');
    $listener   = new PasteResourceListener(new PasteMongoAdapter);
    $resource   = new PhlyRestfully\Resource();
    $resource->setEventManager($events);
    $events->attach($listener);

    $controller = new PhlyRestfully\ResourceController();
    $controller->setResource($resource);
    $controller->setRoute('paste/api');
    $controller->setCollectionHttpOptions(array(
        'GET',
        'POST',
    ));
    $controller->setResourceHttpOptions(array(
        'GET',
    ));
    return $controller;
}

The above example instantiates a listener directly, and attaches it to the event manager instance of a new Resource intance. That resource instance then is attached to a new ResourceController instance, and the route and HTTP OPTIONS are provided. Finally, the controller instance is returned.

Routes

You should create a segment route for each resource that looks like the following:

/path/to/resource[/[:id]]

This single route will then be used for all operations.

If you want to use a route with more segments, and ensure that all captured segments are present when generating the URL, you will need to hook into the HalLinks plugin. As an example, let's consider the following route:

/api/status/:user[/:id]

The "user" segment is required, and should always be part of the URL. However, by default, the ResourceController and the RestfulJsonRenderer will not have knowledge of matched route segments, and will not tell the url() helper to re-use matched parameters.

HalLinks, however, allows you to attach to its createLink event, which gives you the opportunity to provide route parameters. As an example, consider the following listeners:

$user    = $matches->getParam('user');
$helpers = $services->get('ViewHelperManager');
$links   = $helpers->get('HalLinks');
$links->getEventManager()->attach('createLink', function ($e) use ($user) {
    $params = $e->getParam('params');
    $params['user'] = $user;
});

The above would likely happen in a post-routing listener, where we know we routed to a specific controller, and can have access to the route matches. It retrieves the "user" parameter from the route first. Then it retrieves the HalLinks plugin from the view helpers, and attaches to its createLink event; the listener simply assigns the user to the parameters -- which are then passed to the url() helper when creating a link.

Collections

Collections are resources, too, which means they may hold more than simply the set of resources they encapsulate.

By default, the ResourceController simply returns a HalCollection with the collection of resources; if you are using a paginator for the collection, it will also set the current page and number of items per page to render.

You may want to name the collection of resources you are representing. By default, we use "items" as the name; you should use a semantic name. This can be done by either directly setting the collection name on the HalCollection using the setCollectionName() method, or calling the same method on the controller.

You can also set additional attributes. This can be done via a listener; typically, a post-dispatch listener, such as the following, would be a reasonable time to alter the collection instance. In the following, we update the collection to include the count, number per page, and type of objects in the collection.

$events->attach('dispatch', public function ($e) {
    $result = $e->getResult();
    if (!$result instanceof RestfulJsonModel) {
        return;
    }
    if (!$result->isHalCollection()) {
        return;
    }
    $collection = $result->getPayload();
    $paginator  = $collection->collection;
    $collection->setAttributes(array(
        'count'         => $paginator->getTotalItemCount(),
        'per_page'      => $collection->pageSize,
        'resource_type' => 'status',
    ));
}, -1);

Embedding Resources

To follow the HAL specification properly, when you embed resources within resources, they, too, should be rendered as HAL resources. As an example, consider the following object:

{
    "status": "this is my current status",
    "type": "text",
    "user": {
        "id": "matthew",
        "url": "http://mwop.net",
        "github": "weierophinney"
    },
    "id": "afcdeb0123456789afcdeb0123456789"
}

In the above, we have an embedded "user" object. In HAL, this, too, should be treated as a resource.

To accomplish this, simply assign a HalResource value as a resource value. As an example, consider the following pseudo-code for the above example:

$status = new Status(array(
    'status' => 'this is my current status',
    'type'   => 'text',
    'user'   => new HalResource(new User(array(
        'id'     => 'matthew',
        'url'    => 'http://mwop.net',
        'github' => 'weierophinney',
    ), 'matthew', 'user')),
));

When this object is used within a HalResource, it will be rendered as an embedded resource:

{
    "_links": {
        "self": "http://status.dev:8080/api/status/afcdeb0123456789afcdeb0123456789"
    },
    "status": "this is my current status",
    "type": "text",
    "id": "afcdeb0123456789afcdeb0123456789",
    "_embedded": {
        "user": {
            "_links": {
                "self": "http://status.dev:8080/api/user/matthew"
            },
            "id": "matthew",
            "url": "http://mwop.net",
            "github": "weierophinney"
        },
    }
}

This will work in collections as well.

I recommend converting embedded resources to HalResource instances either during hydration, or as part of your Resource listener's mapping logic.

Upgrading

If you were using version 1.0.0 or earlier (the version presented at PHP Benelux 2013), you will need to make some changes to your application to get it to work.

• First, the terminology has changed, as have some class names, to reference "resources" instead of "items"; this is more in line with RESTful terminology.
  • As such, if you had any code using PhlyRestfully\HalItem, it should now reference PhlyRestfully\HalResource. Similarly, in that class, you will access the actual resource object now from the resource property instead of the item property. (This should only affect those post-1.0.0).
  • If you want to create link for an individual resource, use the forResource method of HalLinks, and not the forItem method.
  • InvalidItemException was renamed to InvalidResourceException.
• A number of items were moved from the RestfulJsonModel to the RestfulJsonRenderer.
  • Hydrators
  • The flag for displaying exception backtraces; in fact, you can use the view_manager.display_exceptions configuration setting to set this behavior.
• All results from the ResourceController are now pushed to a payload variable in the view model.
  • Additionally, ApiProblem, HalItem, and HalCollection are first-class objects, and are used as the payload values.
• The Links plugin was renamed to HalLinks, and is now also available as a view helper.

LICENSE

This module is licensed using the BSD 2-Clause License:

Copyright (c) 2013, Matthew Weier O'Phinney
All rights reserved.

Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions are met:

- Redistributions of source code must retain the above copyright notice, this
  list of conditions and the following disclaimer.
- Redistributions in binary form must reproduce the above copyright notice,
  this list of conditions and the following disclaimer in the documentation
  and/or other materials provided with the distribution.

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