Doctrine + DomainEvents

.gitignore

vendor/
db.sqlite
composer.lock

composer.json

{
  "require": {
    "doctrine/orm": "@stable"
  }
}

Domain.php

<?php

namespace MyProject\Domain;

use Doctrine\ORM\Mapping as ORM;
use MyProject\DomainSuperTypes\AggregateRoot;

/**
 * @Entity
 */
class InventoryItem extends AggregateRoot
{
    /**
     * @Id @GeneratedValue @Column(type="integer")
     */
    private $id;
    /**
     * @Column
     */
    private $name;
    /**
     * @Column(type="integer")
     */
    private $counter = 0;

    public function __construct($name)
    {
        $this->name = $name;
        $this->raise('InventoryItemCreated', array('name' => $name));
    }

    public function rename($name)
    {
        $this->name = $name;
        $this->raise('InventoryItemRenamed', array('name' => $name));
    }

    public function checkIn($count)
    {
        $this->counter += $count;
        $this->raise('ItemsCheckedIntoInventory', array('count' => $count));
    }

    public function remove($count)
    {
        $this->counter -= $count;
        $this->raise('ItemsRemovedFromInventory', array('count' => $count));
    }
}

class EchoInventoryListener
{
    public function onInventoryItemCreated($event)
    {
        printf("New item created with name %s\n", $event->name);
    }

    public function onInventoryItemRenamed($event)
    {
        printf("Item was renamed to %s\n", $event->name);
    }

    public function onItemsCheckedIntoInventory($event)
    {
        printf("There were %d new items checked into inventory\n", $event->count);
    }

    public function onItemsRemovedFromInventory($event)
    {
        printf("There were %d items removed from inventory\n", $event->count);
    }
}

domain_events.php

<?php

use Doctrine\ORM\Tools\Setup;
use Doctrine\ORM\Tools\SchemaTool;
use Doctrine\ORM\EntityManager;
use Doctrine\Common\EventManager;
use MyProject\DomainEvents\DirectEventDispatcher;
use MyProject\DomainEvents\DomainEventListener;

use MyProject\Domain\InventoryItem;
use MyProject\Domain\EchoInventoryListener;

require_once __DIR__ . "/vendor/autoload.php";
require_once "DomainEventDispatcher.php";
require_once "DomainSuperTypes.php";
require_once "Domain.php";

$config = Setup::createAnnotationMetadataConfiguration(array(__DIR__));

$conn = array(
    'driver' => 'pdo_sqlite',
    'path' => __DIR__ . '/db.sqlite',
);

$evm = new EventManager();
$evm->addEventListener(
    array('postInsert', 'postUpdate', 'postRemove', 'postFlush'),
    new DomainEventListener()
);
$evm->addEventListener(
    array('onInventoryItemCreated', 'onInventoryItemRenamed', 'onItemsRemovedFromInventory', 'onItemsCheckedIntoInventory'),
    new EchoInventoryListener
);
$entityManager = EntityManager::create($conn, $config, $evm);

$schemaTool = new SchemaTool($entityManager);
try {
    $schemaTool->createSchema(array($entityManager->getClassMetadata(InventoryItem::CLASS)));
} catch(\Exception $e) {
}

$item = new InventoryItem('Cookies');
$item->checkIn(10);

$entityManager->persist($item);
$entityManager->flush();

$item->rename('Chocolate Cookies');
$item->remove(5);

$entityManager->flush();

DomainEventDispatcher.php

<?php

namespace MyProject\DomainEvents;

use Doctrine\ORM\EntityManager;
use MyProject\DomainSuperTypes\AggregateRoot;

class DomainEventListener
{
    private $entities = array();

    public function postPersist($event)
    {
        $this->keepAggregateRoots($event);
    }

    public function postUpdate($event)
    {
        $this->keepAggregateRoots($event);
    }

    public function postRemove($event)
    {
        $this->keepAggregateRoots($event);
    }

    public function postFlush($event)
    {
        $entityManager = $event->getEntityManager();
        $evm = $entityManager->getEventManager();

        foreach ($this->entities as $entity) {
            $class = $entityManager->getClassMetadata(get_class($entity));

            foreach ($entity->popEvents() as $event) {
                $event->setAggregate($class->name, $class->getSingleIdReflectionProperty()->getValue($entity));
                $evm->dispatchEvent("on" . $event->getName(), $event);
            }
        }
        $this->entities = array();
    }

    private function keepAggregateRoots($event)
    {
        $entity = $event->getEntity();

        if (!($entity instanceof AggregateRoot)) {
            return;
        }

        $this->entities[] = $entity;
    }
}

DomainSuperTypes.php

<?php

namespace MyProject\DomainSuperTypes;

use Doctrine\Common\EventArgs;

abstract class AggregateRoot
{
    private $events = array();

    public function popEvents()
    {
        $events = $this->events;
        $this->events = array();

        return $events;
    }

    protected function raise($eventName, array $properties)
    {
        $this->events[] = new DomainEvent($eventName, $properties);
    }
}


class DomainEvent extends EventArgs
{
    private $eventName;
    private $properties;
    private $aggregateClass;
    private $aggregateId;
    private $time;

    public function __construct($eventName, array $properties)
    {
        $this->eventName = $eventName;
        $this->properties = $properties;
        $this->time = microtime(true);
    }

    public function getTime()
    {
        return $this->time;
    }

    public function getName()
    {
        return $this->eventName;
    }

    public function __get($name)
    {
        if (!isset($this->properties[$name])) {
            throw new \RuntimeException("Property '" . $name . "' does not exist on event '" . $this->eventName);
        }

        return $this->properties[$name];
    }

    public function setAggregate($class, $id)
    {
        $this->aggregateClass = $class;
        $this->aggregateId = $id;
    }
}

Hi Benjamin,

I've just stumbled upon your example for implementing domain events and I really like your approach.

I've implemented your example but I get an infinity loop when I save an entity in a event handler:

// Saving another entity in a handler
public function onInventoryItemCreated($event) 
{
        $this->entityManager->persist($fooEntity);
        $this->entityManager->flush();
}

This triggers a flush event again and ends in a infinity loop. Did you experience this issue as well?

EDIT: I solved the problem. Just for future reference: I didn't implemented a popEvents() function but a getEvents() and clearEvents() function so the events got cleared too late and that's the reasons for the infinity loop,

I know I'm three years later in this, but I'm implementing Domain Events with Slim Framework + Doctrine ORM + DDD and used parts of your code, except I wrote a publisher to which I registered subscribers that listen to specific domain events. Anyway, you have a typo with postInsert in:

$evm->addEventListener(
    array('postInsert', 'postUpdate', 'postRemove', 'postFlush'),
    new DomainEventListener()
);

It should be postPersist. I was scratching my head about why it wasn't triggered, but flush was.