Domain Layer

To comprehend how software may be implemented based on hexagonal architecture, let us review an example regarding a restaurant.

Example definition

This restaurant wants to allow a customer to order something by using its website. The website consumes Rest APIs to execute the business logic. Therefore it is necessary to implement a microservice that exposes the functionality to create an order. This use case has the following restriction:

• If a customer has no created orders, it is possible to create a new one
• If a customer has already created orders, it is not possible to create a new one

Model definition

The following diagram depicts the domain layer and what domain objects should be implemented to accomplish the business rules.