Hypertext Application Language for (REpresentational State Transfer) Application Programming Interfaces

Given some conventions, displaying the HAL representation of any entity becomes very easy.

HAL is a json presentation format of the HATEOAS constraint, which is meant to add relations between objects.

It's whole specification is available here http://stateless.co/hal_specification.html

The work is in progress to make it framework agnostic but actually relies on you using symfony/http-foundation, which will change in a close future to use psr6 (while providing a bridge) For the object manager, you are free to choose the one you like, although only doctrine orm has been implemented at the mement. Relation findings relies also a lot on doctrine's ClassMetadata interface, that we should maybe abstract (you can still use your own implementaion)

Usage

composer req bigz/halapi

Symfony bundle

https://github.com/BigZ/HalapiBundle

Full fledged example using symfony (a good starting point for your api)

https://github.com/BigZ/promote-api

Example

use Halapi\AnnotationReader\AnnotationReaderInterface;
use Halapi\ObjectManager\ObjectManagerInterface;
use Halapi\UrlGenerator\UrlGeneratorInterface;
use Psr\Http\Message\ServerRequestInterface;

class EntityController()
{
    /**
     * You can provide your own implementations of those interfaces or use the provided ones.
     */
    public function __construct(
        UrlGeneratorInterface $router,
        AnnotationReaderInterface $annotationReader,
        ObjectManagerInterface $entityManager,
        PagerInterface $pager
    ) {
        $this->router = $router;
        $this->annotationReader = $annotationReader;
        $this->entityManager = $entityManager;
        $this->pager = $pager;
    }

    /**
     * Accessed by the /entities/{id} route
     */
    public function getHalFormattedEntity(ServerRequestInterface $request, Entity $entity)
    {
        $linksRelation = new LinksRelation(
            $this->annotationReader,
            $this->router,
            $this->entityManager,
        );
        $embeddedRelation = new EmbeddedRelation(
            $this->annotationReader,
            $request
        );

        $relationFactory = new RelationFactory([$linksRelation, $embeddedRelation]);
        $builder = new HALAPIBuilder($relationFactory);

        return $builder->gerSerializer()->serialize($entity);
    }

    /**
     * Accessed by the /entities
     */
    public function getHalFormattedCollection(ServerRequestInterface $request, $entityName)
    {
        $linksRelation = new LinksRelation(
            $this->router,
            $this->annotationReader,
            $this->entityManager,
            $request
        );
        $embeddedRelation = new EmbeddedRelation(
            $this->router,
            $this->annotationReader,
            $this->entityManager,
            $request
        );

        $relationFactory = new RelationFactory([$linksRelation, $embeddedRelation]);
        $builder = new HALAPIBuilder($relationFactory);

        $paginationFactory = new PaginationFactory(
            $this->router,
            $this->annotationReader,
            $this->entityManager,
            $this->pager
        );
        $paginatedRepresentation = $paginationFactory->getRepresentation($entityName);

        return $builder->gerSerializer()->serialize($paginatedRepresentation);
    }
}

Resources

List

Pagination

A list will give you a paginated ressource, HAL formatted.

/entities?limit=2&page=2

Filtering

You can filter out results on specific fields.

/entities?filter[id]=5&filteroperator[id]=>

Available operators are >, <, >=, <=, =, != Default operator is =

Sorting

You can sort the result by any property

/entities?sort=-created,title

Entity

Creating new entities

POST /entities

{ "entity": { "name": "eminem", "slug": "eminem", "bio": "rapper from detroit", "labels": [1, 2] } }

will return

{ "id": 2, "name": "eminem", "slug": "eminem", "bio": "rapper from detroit", "_links": { "self": "/artists/2", "labels": [ "/labels/1", "/labels/2" ] } }

PUT & PATCH works the same way

Embedding

By default, relations are not embeded. You can change this behaviour by specifiying wich embedeed entities you need. /entities/1?embed[]=gigs&embed[]=labels

To allow an relation to be embedded, you must add an @Embeddable Annotation to your entity property.

use Halapi\Annotation\Embeddable;

/**
* The Embeddable annoation below is here if you want a custom route for your entity.
* By default, the generator would you "get_'entity's" which is the default behaviour
* of FOSRestBundle.
* @Embeddable("fetch_artists")
*/
class Artist
{
    /**
     * @var int
     *
     * @Expose
     */
    private $id;

    /**
     * @var Labels[]
     *
     * @Embeddable
     */
    protected $labels;
}

Roadmap to production readyness

• (MUST) Improve coverage
• (MUST) Implement sparse fieldset
• (MUST) Implement deep resource inclusion
• (SHOULD) support IN filter operator
• (SHOULD) Refactor using propertyinfo component
• (SHOULD) USE doctrine/reflection instead of doctrine/common
• (SHOULD) Be able to serialize to any other hateoas format. Not so easy with jms...