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<?php |
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namespace Domain\Aggregates; |
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use Domain\Eventing\EventStore; |
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use Domain\Eventing\EventBus; |
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use Domain\Identity\Identity; |
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use Domain\Snapshotting\SnapshotStore; |
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use Domain\Snapshotting\SnapshottingPolicy; |
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use Domain\Snapshotting\Policy\IntervalBased; |
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use Domain\Eventing\CommittedEvents; |
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/** |
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* Base class for concrete repositories which contains some sane defaults |
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* |
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* @author Sebastiaan Hilbers <[email protected]> |
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*/ |
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abstract class BaseAggregateRepository implements AggregateRepository |
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{ |
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/** |
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* @var EventStore |
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*/ |
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private $eventStore; |
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/** |
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* @var EventBus |
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*/ |
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private $eventBus; |
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/** |
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* @var SnapshotStore |
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*/ |
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private $snapshotStore; |
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/** |
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* @var SnapshottingPolicy |
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*/ |
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private $snapshottingPolicy; |
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/** |
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* @param EventStore $eventStore |
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* @param EventBus $eventBus |
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* @param SnapshotStore $snapshotStore |
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* @param SnapshottingPolicy $policy |
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*/ |
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public function __construct( |
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EventStore $eventStore, |
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EventBus $eventBus = null, |
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SnapshotStore $snapshotStore = null, |
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SnapshottingPolicy $policy = null |
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) { |
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$this->eventStore = $eventStore; |
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$this->eventBus = $eventBus; |
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$this->snapshotStore = $snapshotStore; |
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// default policy sets up a 100 event interval for snapshotting |
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if (!is_null($snapshotStore) && is_null($policy)) { |
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$policy = new IntervalBased(100); |
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} |
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$this->snapshottingPolicy = $policy; |
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} |
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/** |
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* To store the updates made to an Aggregate, we only need to |
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* commit the latest recorded events to the EventStore. |
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* |
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* An eventbus can handle eventual or direct consistency. |
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* |
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* Snapsnots could be made if the policy allows it and this repo is |
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* constructed with a storage for storing snapshots. |
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* |
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* @param AggregateRoot $aggregate |
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* @return CommittedEvents |
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*/ |
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public function save(AggregateRoot $aggregate) |
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{ |
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$uncommitted = $aggregate->getChanges(); |
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$committedStream = $this->eventStore->commit($uncommitted); |
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// consider eventual consistency |
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if (!is_null($this->eventBus)) { |
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$this->eventBus->publish($committedStream); |
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} |
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// do we need to create a snapshot at this point? |
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if (!is_null($this->snapshotStore) && $this->snapshottingPolicy->shouldCreateSnapshot($aggregate)) { |
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$this->saveSnapshot($aggregate); |
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} |
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// remove changes on aggregate from memory |
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$aggregate->clearChanges(); |
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return $committedStream; |
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} |
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/** |
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* Fetching a single Aggregate is extremely easy: all we need to do is |
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* reconstitute it from its history! Compare that to the complexity |
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* of traditional ORMs. |
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* |
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* @param Identity $aggregateId |
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* @return AggregateRoot |
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*/ |
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public function get(Identity $aggregateId) |
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{ |
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if (!is_null($this->snapshotStore)) { |
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if (!($snapshot = $this->loadSnapshot($aggregateId))) { |
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$missing = $this->eventStore->getAggregateHistoryFor($aggregateId, $snapshot->getVersion()); |
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if ($missing->count() > 0) { |
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$snapshot->correctMissingHistory($missing); |
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} |
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return $snapshot->getAggregate(); |
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} |
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} |
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$aggregateHistory = $this->eventStore->getAggregateHistoryFor($aggregateId); |
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$fqn = $this->getAggregateRootFqcn(); |
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return $fqn::reconstituteFrom($aggregateHistory); |
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} |
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/** |
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* Concrete repositories should define the Aggregate's FQCN |
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* |
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* @return string |
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*/ |
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abstract protected function getAggregateRootFqcn(); |
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/** |
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* Load a aggregate snapshot from the storage |
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* |
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* @param \Domain\Identity\Identity $id |
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* @return Snapshot |
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* @throws \Exception when no snapshotStore was attached |
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*/ |
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public function loadSnapshot(Identity $id) |
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{ |
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if (is_null($this->snapshotStore)) { |
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throw new \Exception('Unable to get snapshot; No store attached'); |
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} |
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return $this->snapshotStore->get($id); |
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} |
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/** |
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* Save the aggregate state as single snapshot instead of multiple history events |
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* |
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* @param \Domain\Aggregates\AggregateRoot $aggregate |
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* @return type |
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* @throws \Exception when no snapshotStore was attached |
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*/ |
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public function saveSnapshot(AggregateRoot $aggregate) |
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{ |
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if (is_null($this->snapshotStore)) { |
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throw new \Exception('Unable to create snapshot; No store attached'); |
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} |
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if ($aggregate->hasChanges()) { |
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$aggregate = $aggregate::reconstituteFrom( |
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new CommittedEvents( |
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$aggregate->getIdentity(), |
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$aggregate->getChanges()->getEvents() |
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) |
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); |
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} |
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return $this->snapshotStore->save($aggregate); |
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} |
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} |
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