Zero external framework dependencies (no Spring, no Hibernate, no Jackson). Changes only when the business model changes. Ports (The Interfaces)
You can create the following maven project structure.
Hexagonal architecture, also known as ports and adapters architecture, is a design pattern that separates the application's business logic from its infrastructure and external dependencies. This architecture is particularly useful for building robust, scalable, and maintainable software systems. In this article, we'll explore how to design a hexagonal architecture with Java and provide a feature-driven design approach.
Because the domain layer has zero infrastructure dependencies, you can write blistering-fast unit tests using plain JUnit 5 or Mockito. You do not need to boot up a slow Spring Application Context ( @SpringBootTest ). Hexagonal architecture, also known as ports and adapters
A DTO (a flattened object used for API responses) should never be in your Domain core. Your Primary Adapter (e.g., the REST Controller) is responsible for mapping the Domain object into the DTO. The Domain core is only aware of Domain objects (Entities/Value Objects).
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Concrete implementations that connect external systems (like databases, REST APIs, or message brokers) to the ports. The Dependency Inversion Principle Your Primary Adapter (e.g.
This layer implements the outbound ports, such as using JPA/Hibernate for database interaction.
Java's strong typing and interface-driven approach make it an ideal language for implementing Hexagonal Architecture. Here's a typical project structure:
public interface AuthenticationService boolean authenticate(String username, String password); Zero external framework dependencies (no Spring
public class UserService private final UserRepository userRepository;
@Component @RequiredArgsConstructor public class UserJpaAdapter implements UserRepositoryPort private final UserJpaRepository jpaRepository; // Spring Data @Override public User save(User user) UserEntity entity = UserMapper.toEntity(user); return UserMapper.toDomain(jpaRepository.save(entity)); // ... Use code with caution. Why Use Hexagonal Architecture in 2021+?