Clear boundaries make the codebase easier to understand and evolve.
Java's strong typing and interface-driven approach make it an ideal language for implementing Hexagonal Architecture. Here's a typical project structure:
First, we define our domain entity. It contains the business rules. Clear boundaries make the codebase easier to understand
package com.bank.adapters.outbound; import com.bank.domain.model.Account; import com.bank.ports.outbound.AccountRepositoryPort; import org.springframework.stereotype.Component; import java.util.UUID; @Component public class AccountPersistenceAdapter implements AccountRepositoryPort private final SpringDataAccountRepository repository; public AccountPersistenceAdapter(SpringDataAccountRepository repository) this.repository = repository; @Override public Account load(UUID accountId) AccountEntity entity = repository.findById(accountId) .orElseThrow(() -> new RuntimeException("Account not found")); return new Account(entity.getId(), entity.getBalance()); @Override public void save(Account account) AccountEntity entity = new AccountEntity(account.getAccountId(), account.getBalance()); repository.save(entity); Use code with caution. Organizing Package Structures
[ REST API / CLI ] --> ( Driving Adapter ) | v [ Driving Port ] | v +--------------------------+ | | | Core Domain Logic | | (Entities & Services) | | | +--------------------------+ | v [ Driven Port ] | v ( Driven Adapter ) | v [ Database / SMS ] The Domain Hexagon (The Core) It contains the business rules
: The heart of the application, containing business logic and rules. It should be independent of any external frameworks or technologies.
This separation is achieved through three main conceptual layers: It should be independent of any external frameworks
Many developers search for terms like "designing hexagonal architecture with java pdf free 2021 download" looking for a quick textbook or code sample.
public interface ProductRepositoryPort Product save(Product product); Optional<Product> findById(String id);
In traditional layered architectures, business logic is often sandwiched between the user interface and the database, making it difficult to test or modify without breaking other components. Hexagonal Architecture flips this by placing the Domain Layer (the "inside") at the center of the application.
The architecture got its name from its visual representation, where each of the different "edges" or connection points of the system forms a distinct side of a hexagon. However, the number six is arbitrary—the key takeaway is the presence of multiple ports and adapters. The goal is to create a system where all inputs and outputs are placed at the edges, allowing the central application core (the "Heart") to remain completely independent of any external technology.