Understanding the role of the Application layer
The Application layer serves as a thin layer that coordinates our domain objects and services to accomplish meaningful user tasks. While our domain model provides the building blocks, tasks, projects, deadlines, it’s the Application layer that assembles these pieces into useful features.
The Application layer serves another critical function: information hiding. In Chapter 4, we saw how domain entities hide their internal state and implementation details. The Application layer extends this principle across architectural boundaries, hiding infrastructure details from the domain and domain complexities from external interfaces. This deliberate hiding of information is what makes the additional effort of creating ports, adapters, and request/response models worthwhile. By exposing only what’s necessary through carefully designed interfaces, we create a system where components can evolve independently yet work together...
