Axon Aggregate

Waiter.kt

@Aggregate
final class Waiter() {
   ...
    @CommandHandler
    constructor(command: HireWaiterCommand) : this() {
        AggregateLifecycle.apply(WaiterHiredEvent(id = command.id, name = command.name))
    }

    @CommandHandler
    fun handle(command: TakeOrderCommand) {
        if(command.items.any { this.outOfStockItems.contains(it.name) }){
            throw ItemsOutOfStockException(this.outOfStockItems.toList())
        }
        AggregateLifecycle.apply(OrderTakenEvent(command.waiterId, command.orderId, items = command.items))
    }

    @EventSourcingHandler
    fun on(event: WaiterHiredEvent) {
        this.id = event.id
    }

    @EventSourcingHandler
    fun on(event: OrderTakenEvent) {
        this.orders.add( Order(event.orderId, event.items))
    }
  ...
}