Update two aggregate in same time

Axon Framework
1

I have three catalogs, A, B and C, i want to add a new product to the catalog B.
I have an aggregate for product, so i create a command CreateProductCommand which is responsible for creating the product.
In the same time i want to update the products list in the CatalogAggregate for a specific catalog (for my example the catalog B). What’s the best approach to do that ?

@Aggregate
public class CatalogAggregate {

	@AggregateIdentifier
	private String catalogtId;

	private List<Product> products;
	
}

@Aggregate
public class ProductAggregate {

	@AggregateIdentifier
	private String productId;
	
	private String name;
	
	private short price;
	
}

public String createProduct(Product product) {
	return (String) commandGateway.sendAndWait(new CreateProductCommand(UUID.randomUUID().toString(), product.getName(), product.getPrice()));
}
2

Hi Aymen,

Thanks for using our forum. This is a suggestion how you can do it using Axon:
The Product aggregate:

    import java.util.UUID;

    import org.axonframework.commandhandling.CommandHandler;
    import org.axonframework.eventsourcing.EventSourcingHandler;
    import org.axonframework.modelling.command.AggregateIdentifier;
    import org.axonframework.modelling.command.AggregateLifecycle;
    import org.axonframework.spring.stereotype.Aggregate;

    import io.axoniq.dev.samples.api.CreateProductCommand;
    import io.axoniq.dev.samples.api.ProductCreatedEvent;

    @Aggregate
    public class ProductAggregate {
        @AggregateIdentifier
        private UUID productId;

        @CommandHandler
        ProductAggregate(CreateProductCommand command){
            AggregateLifecycle.apply(new ProductCreatedEvent(command.getProductId()));
        }

        @EventSourcingHandler
        public void on(ProductCreatedEvent event){
            this.productId = event.getProductId();
        }
    }

And the CatalogAggregate

    import static org.axonframework.modelling.command.AggregateLifecycle.apply;

    import java.util.List;
    import java.util.UUID;

    import org.axonframework.commandhandling.CommandHandler;
    import org.axonframework.eventsourcing.EventSourcingHandler;
    import org.axonframework.modelling.command.AggregateIdentifier;
    import org.axonframework.modelling.command.AggregateMember;
    import org.axonframework.spring.stereotype.Aggregate;

    import io.axoniq.dev.samples.api.AddProductToCatalogCommand;
    import io.axoniq.dev.samples.api.CatalogCreatedEvent;
    import io.axoniq.dev.samples.api.CreateCatalogCommand;
    import io.axoniq.dev.samples.api.ProductAddedToCatalogEvent;

    @Aggregate
    public class CatalogAggregate {
        @AggregateIdentifier
        private UUID catalogId;

        @AggregateMember
        private List<UUID> products;

        @CommandHandler
        public CatalogAggregate(CreateCatalogCommand command) {
            apply(new CatalogCreatedEvent(command.getCatalogId()));
        }

        @CommandHandler
        public void handle(AddProductToCatalogCommand command){
            apply(new ProductAddedToCatalogEvent(command.getCatalogId(), command.getProductId()))
        }

        @EventSourcingHandler
        public void on(CatalogCreatedEvent event){
            this.catalogId = event.getCatalogId();
        }

        @EventSourcingHandler
        public void on (ProductAddedToCatalogEvent event){
            this.products.add(event.getProductId());
        }
    }

If you have your aggregates set up like this you can listen to the ProductCreatedEvent in an event handling component and send a command to the CatalogAggregate:

    @Component
    public class ProductEventHandler {

        @EventHandler
        public void on(ProductCreatedEvent event, CommandGateway commandGateway){
            commandGateway.send(new AddProductToCatalogCommand(event.getProductId(), event.getProductId()));
        }
    }

I hope this makes sense.
I would like to mention that on Wednesday my colleague @Steven_van_Beelen will provide a free webinar explaining DDD,CQRS and ES and the basics of Axon Framework. https://axoniq.io/event-overview/fast-lane-axon-framework-online-training-nr-10

Kind regards,

Yvonne

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