Marks an event class for automatic outbox persistence.

When an event annotated with @OutboxEvent is published via Spring's ApplicationEventPublisher, it will be automatically persisted to the outbox database before (optionally) being delivered to event listeners. This ensures durability of events and enables reliable event propagation.

Recommended Usage with @DomainEvents: The best practice is to use @DomainEvents in your Aggregate Root combined with @OutboxEvent on your event classes. This way, Spring Data JPA automatically publishes domain events after a successful transaction commit, and the OutboxEvent multicaster persists them to the outbox.

@Entity
class Customer {
    @DomainEvents
    fun domainEvents(): Collection<Any> = this.events

    fun activate() {
        this.events.add(CustomerActivatedEvent(this.id))
    }
}

@OutboxEvent(aggregateId = "customerId")
data class CustomerActivatedEvent(val customerId: String) : DomainEvent

Then publish via repository.save():

@Transactional
fun activateCustomer(customerId: String) {
    val customer = repository.findById(customerId)
    customer.activate()
    repository.save(customer)  // triggers @DomainEvents -> @OutboxEvent -> outbox persistence
}