Pushing Data to Clients Using the Mercure Protocol¶

// src/Controller/PublishController.php
namespace App\Controller;

use Symfony\Component\HttpFoundation\Response;
use Symfony\Component\Mercure\Update;
use Symfony\Component\Messenger\MessageBusInterface;

class PublishController
{
    public function __invoke(MessageBusInterface $bus): Response
    {
        $update = new Update(
            'http://example.com/books/1',
            json_encode(['status' => 'OutOfStock'])
        );

        // Sync, or async (RabbitMQ, Kafka...)
        $bus->dispatch($update);

        return new Response('published!');
    }
}

// src/Controller/DiscoverController.php
namespace App\Controller;

use Symfony\Bundle\FrameworkBundle\Controller\AbstractController;
use Symfony\Component\HttpFoundation\JsonResponse;
use Symfony\Component\HttpFoundation\Request;
use Symfony\Component\WebLink\Link;

class DiscoverController extends AbstractController
{
    public function __invoke(Request $request): JsonResponse
    {
        // This parameter is automatically created by the MercureBundle
        $hubUrl = $this->getParameter('mercure.default_hub');

        // Link: <http://localhost:3000/.well-known/mercure>; rel="mercure"
        $this->addLink($request, new Link('mercure', $hubUrl));

        return $this->json([
            '@id' => '/books/1',
            'availability' => 'https://schema.org/InStock',
        ]);
    }
}

// src/Controller/Publish.php
namespace App\Controller;

use Symfony\Component\HttpFoundation\Response;
use Symfony\Component\Mercure\PublisherInterface;
use Symfony\Component\Mercure\Update;

class PublishController
{
    public function __invoke(PublisherInterface $publisher): Response
    {
        $update = new Update(
            'http://example.com/books/1',
            json_encode(['status' => 'OutOfStock']),
            true // private
        );

        // Publisher's JWT must contain this topic, a URI template it matches or * in mercure.publish or you'll get a 401
        // Subscriber's JWT must contain this topic, a URI template it matches or * in mercure.subscribe to receive the update
        $publisher($update);

        return new Response('private update published!');
    }
}

// src/Controller/DiscoverController.php
namespace App\Controller;

use Lcobucci\JWT\Builder;
use Lcobucci\JWT\Signer\Hmac\Sha256;
use Lcobucci\JWT\Signer\Key;
use Symfony\Bundle\FrameworkBundle\Controller\AbstractController;
use Symfony\Component\HttpFoundation\Cookie;
use Symfony\Component\HttpFoundation\Request;
use Symfony\Component\HttpFoundation\Response;
use Symfony\Component\WebLink\Link;

class DiscoverController extends AbstractController
{
    public function __invoke(Request $request): Response
    {
        $hubUrl = $this->getParameter('mercure.default_hub');
        $this->addLink($request, new Link('mercure', $hubUrl));

        $token = (new Builder())
            // set other appropriate JWT claims, such as an expiration date
            ->withClaim('mercure', ['subscribe' => ["http://example.com/books/1"]]) // can also be a URI template, or *
            ->getToken(new Sha256(), new Key($this->getParameter('mercure_secret_key'))); // don't forget to set this parameter! Test value: !ChangeMe!

        $response = $this->json(['@id' => '/demo/books/1', 'availability' => 'https://schema.org/InStock']);
        $cookie = Cookie::create('mercureAuthorization')
            ->withValue($token)
            ->withPath('/.well-known/mercure')
            ->withSecure(true)
            ->withHttpOnly(true)
            ->withSameSite('strict')
        ;
        $response->headers->setCookie($cookie);

        return $response;
    }
}

// src/Mercure/MyJwtProvider.php
namespace App\Mercure;

final class MyJwtProvider
{
    public function __invoke(): string
    {
        return 'the-JWT';
    }
}

// src/Entity/Book.php
namespace App\Entity;

use ApiPlatform\Core\Annotation\ApiResource;
use Doctrine\ORM\Mapping as ORM;

/**
* @ApiResource(mercure=true)
* @ORM\Entity
*/
class Book
{
    /**
     * @ORM\Id
     * @ORM\Column
     */
    public $name;

    /**
     * @ORM\Column
     */
    public $status;
}

// tests/Functional/Fixtures/PublisherStub.php
namespace App\Tests\Functional\Fixtures;

use Symfony\Component\Mercure\PublisherInterface;
use Symfony\Component\Mercure\Update;

class PublisherStub implements PublisherInterface
{
    public function __invoke(Update $update): string
    {
        return '';
    }
}

# config/services_test.yaml
App\Tests\Functional\Fixtures\PublisherStub:
    decorates: mercure.hub.default.publisher