Designing Hexagonal Architecture With Java Pdf Free 2021 ((top)) | Download

Domain objects that contain both data and business rules.

@RestController // Adapter for Web public class WithdrawController private final WithdrawMoneyPort withdrawUseCase; // The Port

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public void withdraw(Money amount) if (balance.lessThan(amount)) throw new InsufficientFundsException(); Domain objects that contain both data and business rules

: Adapters are the concrete implementations of the ports. They are the glue that connects the external world to the core. An incoming adapter could be a REST controller or a Kafka listener. An outgoing adapter could be a JdbcUserRepository that implements a UserRepository port. The beauty of this system is that you can "plug in" different adapters for different purposes without ever touching the core business logic.

package com.example.order.adapters.outbound; import com.example.order.domain.Order; import com.example.order.ports.outbound.OrderRepositoryPort; import org.springframework.stereotype.Repository; @Repository public class OrderRepositoryAdapter implements OrderRepositoryPort private final SpringDataOrderRepository repository; public OrderRepositoryAdapter(SpringDataOrderRepository repository) this.repository = repository; @Override public void save(Order order) OrderEntity entity = new OrderEntity(order.getId(), order.getProduct(), order.getPrice(), order.getStatus()); repository.save(entity); Use code with caution.

The core business logic sits in the absolute center. It does not know about databases, web frameworks, or UI components. Instead, it defines interfaces (Ports). External systems implement or drive these interfaces using Adapters. 3. The Three Core Pillars: Domain, Ports, and Adapters An incoming adapter could be a REST controller

package com.example.order.ports.inbound; import com.example.order.domain.Order; import java.math.BigDecimal; import java.util.UUID; public interface CreateOrderUseCase Order createOrder(String product, BigDecimal price); Use code with caution.

Navigating the code requires jumping through interfaces, which can slightly increase initial cognitive load for junior developers. Resources and Next Steps

package com.example.order.adapters.inbound; import com.example.order.domain.Order; import com.example.order.ports.inbound.CreateOrderUseCase; import org.springframework.http.ResponseEntity; import org.springframework.web.bind.annotation.*; import java.math.BigDecimal; @RestController @RequestMapping("/orders") public class OrderController private final CreateOrderUseCase createOrderUseCase; public OrderController(CreateOrderUseCase createOrderUseCase) this.createOrderUseCase = createOrderUseCase; @PostMapping public ResponseEntity create(@RequestParam String product, @RequestParam BigDecimal price) Order order = createOrderUseCase.createOrder(product, price); return ResponseEntity.ok(order); Use code with caution. package com

package com.example.order.adapters.inbound; import com.example.order.domain.Order; import com.example.order.ports.inbound.CreateOrderUseCase; import org.springframework.http.ResponseEntity; import org.springframework.web.bind.annotation.*; import java.math.BigDecimal; @RestController @RequestMapping("/orders") public class OrderWebAdapter private final CreateOrderUseCase createOrderUseCase; // Direct dependency only on the Inbound Port interface public OrderWebAdapter(CreateOrderUseCase createOrderUseCase) this.createOrderUseCase = createOrderUseCase; @PostMapping public ResponseEntity create(@RequestParam String product, @RequestParam BigDecimal price) Order order = createOrderUseCase.createOrder(product, price); return ResponseEntity.ok(order); Use code with caution. Step 5: The Secondary Adapter (Database Persistence)

Aligning aggregates with hexagonal boundaries. Conclusion

package com.example.order.domain; import com.example.order.ports.inbound.CreateOrderUseCase; import com.example.order.ports.outbound.OrderRepositoryPort; import java.math.BigDecimal; import java.util.UUID; public class OrderService implements CreateOrderUseCase private final OrderRepositoryPort orderRepositoryPort; public OrderService(OrderRepositoryPort orderRepositoryPort) this.orderRepositoryPort = orderRepositoryPort; @Override public Order createOrder(String product, BigDecimal price) Order order = new Order(UUID.randomUUID(), product, price, "CREATED"); order.validate(); orderRepositoryPort.save(order); return order; Use code with caution. Step 4: Build the Adapters (The Outside)