Using your own event serializer | laravel-event-sourcing | Spatie

 SPATIE

  Laravel Event Sourcing
=========================

spatie.be/open-source

  [Docs](https://spatie.be/docs)  [Laravel-event-sourcing](https://spatie.be/docs/laravel-event-sourcing/v6)  Advanced-usage  Using your own event serializer

 Version   v7   v6   v5   v4   v3   v2   v1

 Other versions for crawler [v7](https://spatie.be/docs/laravel-event-sourcing/v7) [v6](https://spatie.be/docs/laravel-event-sourcing/v6) [v5](https://spatie.be/docs/laravel-event-sourcing/v5) [v4](https://spatie.be/docs/laravel-event-sourcing/v4) [v3](https://spatie.be/docs/laravel-event-sourcing/v3) [v2](https://spatie.be/docs/laravel-event-sourcing/v2) [v1](https://spatie.be/docs/laravel-event-sourcing/v1)

- [ Introduction ](https://spatie.be/docs/laravel-event-sourcing/v6/introduction)
- [ Support us ](https://spatie.be/docs/laravel-event-sourcing/v6/support-us)
- [ Requirements ](https://spatie.be/docs/laravel-event-sourcing/v6/requirements)
- [ Installation & setup ](https://spatie.be/docs/laravel-event-sourcing/v6/installation-setup)
- [ Questions and issues ](https://spatie.be/docs/laravel-event-sourcing/v6/questions-issues)
- [ Changelog ](https://spatie.be/docs/laravel-event-sourcing/v6/changelog)
- [ Upgrading ](https://spatie.be/docs/laravel-event-sourcing/v6/upgrading)
- [ Resources and alternatives ](https://spatie.be/docs/laravel-event-sourcing/v6/resources-and-alternatives)
- [ About us ](https://spatie.be/docs/laravel-event-sourcing/v6/about-us)

Getting familiar with event sourcing
------------------------------------

- [ Introduction ](https://spatie.be/docs/laravel-event-sourcing/v6/getting-familiar-with-event-sourcing/introduction)
- [ The traditional application ](https://spatie.be/docs/laravel-event-sourcing/v6/getting-familiar-with-event-sourcing/the-traditional-application)
- [ Using projectors to transform events ](https://spatie.be/docs/laravel-event-sourcing/v6/getting-familiar-with-event-sourcing/using-projectors-to-transform-events)
- [ Using aggregates to make decisions based on the past ](https://spatie.be/docs/laravel-event-sourcing/v6/getting-familiar-with-event-sourcing/using-aggregates-to-make-decisions-based-on-the-past)

Using projectors
----------------

- [ Writing your first projector ](https://spatie.be/docs/laravel-event-sourcing/v6/using-projectors/writing-your-first-projector)
- [ Creating and registering projectors ](https://spatie.be/docs/laravel-event-sourcing/v6/using-projectors/creating-and-configuring-projectors)
- [ Making sure events get handled in the right order ](https://spatie.be/docs/laravel-event-sourcing/v6/using-projectors/making-sure-events-get-handled-in-the-right-order)
- [ Thinking in events ](https://spatie.be/docs/laravel-event-sourcing/v6/using-projectors/thinking-in-events)

Using reactors
--------------

- [ Writing your first reactor ](https://spatie.be/docs/laravel-event-sourcing/v6/using-reactors/writing-your-first-reactor)
- [ Creating and configuring reactors ](https://spatie.be/docs/laravel-event-sourcing/v6/using-reactors/creating-and-configuring-reactors)

Using aggregates
----------------

- [ Writing your first aggregate ](https://spatie.be/docs/laravel-event-sourcing/v6/using-aggregates/writing-your-first-aggregate)
- [ Creating and configuring aggregates ](https://spatie.be/docs/laravel-event-sourcing/v6/using-aggregates/creating-and-configuring-aggregates)
- [ Testing aggregates ](https://spatie.be/docs/laravel-event-sourcing/v6/using-aggregates/testing-aggregates)
- [ Snapshots ](https://spatie.be/docs/laravel-event-sourcing/v6/using-aggregates/snapshots)

Advanced usage
--------------

- [ Preparing events ](https://spatie.be/docs/laravel-event-sourcing/v6/advanced-usage/preparing-events)
- [ Replaying events ](https://spatie.be/docs/laravel-event-sourcing/v6/advanced-usage/replaying-events)
- [ Storing metadata ](https://spatie.be/docs/laravel-event-sourcing/v6/advanced-usage/storing-metadata)
- [ Handling exceptions ](https://spatie.be/docs/laravel-event-sourcing/v6/advanced-usage/handling-exceptions)
- [ Discovering projectors and reactors ](https://spatie.be/docs/laravel-event-sourcing/v6/advanced-usage/discovering-projectors-and-reactors)
- [ Using your own event storage model ](https://spatie.be/docs/laravel-event-sourcing/v6/advanced-usage/using-your-own-event-storage-model)
- [ Using your own event storage repository ](https://spatie.be/docs/laravel-event-sourcing/v6/advanced-usage/using-your-own-event-storage-repository)
- [ Using your own event serializer ](https://spatie.be/docs/laravel-event-sourcing/v6/advanced-usage/using-your-own-event-serializer)
- [ Using aliases for stored event classes ](https://spatie.be/docs/laravel-event-sourcing/v6/advanced-usage/using-aliases-for-stored-event-classes)
- [ Adding and Removing Projectors and Reactors ](https://spatie.be/docs/laravel-event-sourcing/v6/advanced-usage/adding-and-removing-projectors-and-reactors)
- [ Aggregate Partials ](https://spatie.be/docs/laravel-event-sourcing/v6/advanced-usage/aggregate-partials)
- [ Event Queries ](https://spatie.be/docs/laravel-event-sourcing/v6/advanced-usage/event-queries)
- [ Commands ](https://spatie.be/docs/laravel-event-sourcing/v6/advanced-usage/commands)

      You are viewing the documentation for **an older version** of this package. You can check the version you are using with the following command:

 `                                    composer show spatie/laravel-event-sourcing                                                                                                                                                                                                                                    `

Using your own event serializer
===============================

###  On this page

1. [ Upgrading Events ](#content-upgrading-events)
2. [ Want to know more? ](#content-want-to-know-more)

Events will be serialized by the `Spatie\EventSourcing\EventSerializers\JsonEventSerializer`. Like the name implies, this class can serialize an event to json so it can be easily stored in a `json` column in the database.

You can specify your own serializer by creating a class that implements `Spatie\EventSourcing\EventSerializers\EventSerializer` and specifying the class in the `event_serializer` key of the `event-sourcing.php` config file.

This is the content of the `EventSerializer` interface:

```
namespace Spatie\EventSourcing\EventSerializers;

use Spatie\EventSourcing\ShouldBeStored;

interface EventSerializer
{
    public function serialize(ShouldBeStored $event): string;

    public function deserialize(string $eventClass, string $json, string $metadata): ShouldBeStored;
}
```

Upgrading Events
--------------------------------------------------------------------------------------------------------

If an event payload has changed overtime, old events can be "upgraded" to the new payload on the fly in the event serializer.

Using our larabank example, let's imagine that we've gone international and our new accepting international payments. Our `MoneyAdded` events will need to have an additional field for the currency.

```
class UpgradeSerializer extends JsonEventSerializer
{
    public function deserialize(string $eventClass, string $json, string $metadata = null): ShouldBeStored
    {
        $event = parent::deserialize($eventClass, $json, $metadata);

        // all currency was USD before we started accepting other currencies
        if (empty($event->currency)) {
            $event->currency = 'USD';
        }

        return $event;
    }
}
```

Want to know more?
------------------------------------------------------------------------------------------------------------

Our course, [Event Sourcing in Laravel](https://event-sourcing-laravel.com/) covers this topic in depth:

- 16. Event Versioning