Modular Hexagonal Architecture Project

This project refers to my latest article:

• Clean and Modular Java: A Hexagonal Architecture Approach

This project demonstrates a Hexagonal (Ports and Adapters) architecture in a modular Maven setup.
It separates concerns by using three main modules:

Layer/Module	Depends On	Explanation
domain	—	Pure domain logic. No external dependencies.
application	domain	Application services orchestrate domain logic.
infrastructure	application, domain	Contains adapters and framework code (Spring), wires up everything.

Key Principles

Domain layer: Pure business logic. No knowledge of frameworks like Spring.
Application layer: Orchestrates use cases and uses domain interfaces.
Infrastructure layer: Wires up frameworks (Spring, DB, APIs) and implements adapters.

Domain module

This module contains only pure domain logic. It has no external dependencies and is completely agnostic to any frameworks or infrastructure concerns.

What’s inside?

• Domain models (Entities)
• Domain interfaces (ports)

What’s not inside?

• No Spring annotations
• No framework dependencies
• No infrastructure-related code

Application module

This module defines use cases and orchestrates domain logic by leveraging the interfaces (ports) from the domain module.
It coordinates domain interactions and ensures business rules are applied consistently.

What’s inside?

• Application services (e.g., CreateProductService, UpdateProductService)
• Use case orchestration

What’s not inside?

• No direct framework dependencies
• No infrastructure code

Infrastructure module

This module contains adapters and all the framework-related code, like Spring Boot configuration, REST APIs, br.com.ricas.database access, and external integrations.

What’s inside?

• Spring Boot application starter
• Adapters implementing domain interfaces (e.g., br.com.ricas.database repositories)
• Configuration and integration with external systems

What’s not inside?

• No business logic or domain-specific rules
• No pure application logic (delegates to application services)

Running the Application

To run the application and connect it to MongoDB Atlas, use the following commands:

On macOS/Linux:

export MONGODB_URI="<YOUR_CONNECTION_STRING>"
cd infrastructure
mvn spring-boot:run