Document Skill original
Rendu depuis le dépôt source en conservant titres, exemples, code, tableaux, liens et images.
When to Use
Load this skill when:
- Designing a new Java service with clean, testable layers
- Refactoring Spring code to isolate the domain from frameworks
- Supporting multiple adapters (REST + messaging, JPA + Mongo)
- Enforcing dependency direction and clear module boundaries
Critical Patterns
Pattern 1: Domain is pure
Domain has no framework annotations, no persistence concerns, and no I/O.
Pattern 2: Application orchestrates
Application defines use cases and ports, calling domain logic and delegating I/O to ports.
Pattern 3: Infrastructure adapts
Infrastructure implements ports and wires adapters (controllers, repositories, clients).
Code Examples
Example 1: Domain model + output port
java
package com.acme.order.domain;
public record OrderId(String value) { }
public final class Order {
private final OrderId id;
private final Money total;
public Order(OrderId id, Money total) {
this.id = id;
this.total = total;
}
public OrderId id() { return id; }
public Money total() { return total; }
}java
package com.acme.order.application.port;
import com.acme.order.domain.Order;
import com.acme.order.domain.OrderId;
public interface OrderRepositoryPort {
OrderId nextId();
void save(Order order);
}Example 2: Application use case + input port
java
package com.acme.order.application.usecase;
import com.acme.order.application.port.OrderRepositoryPort;
import com.acme.order.domain.Order;
import com.acme.order.domain.OrderId;
import com.acme.order.domain.Money;
public interface PlaceOrderUseCase {
OrderId place(Money total);
}
public final class PlaceOrderService implements PlaceOrderUseCase {
private final OrderRepositoryPort repository;
public PlaceOrderService(OrderRepositoryPort repository) {
this.repository = repository;
}
@Override
public OrderId place(Money total) {
OrderId id = repository.nextId();
Order order = new Order(id, total);
repository.save(order);
return id;
}
}Example 3: Infrastructure adapter + wiring
java
package com.acme.order.infrastructure.persistence;
import com.acme.order.application.port.OrderRepositoryPort;
import com.acme.order.domain.Order;
import com.acme.order.domain.OrderId;
import org.springframework.stereotype.Repository;
@Repository
public final class OrderJpaAdapter implements OrderRepositoryPort {
private final SpringOrderRepository repository;
private final OrderMapper mapper;
public OrderJpaAdapter(SpringOrderRepository repository, OrderMapper mapper) {
this.repository = repository;
this.mapper = mapper;
}
@Override
public OrderId nextId() {
return new OrderId(java.util.UUID.randomUUID().toString());
}
@Override
public void save(Order order) {
repository.save(mapper.toEntity(order));
}
}Anti-Patterns
Don't: Put framework annotations in domain
java
// BAD: domain tied to JPA
@jakarta.persistence.Entity
public class Order {
@jakarta.persistence.Id
private String id;
}Don't: Call infrastructure directly from domain
java
// BAD: domain depends on Spring repository
public class Order {
private final SpringOrderRepository repository;
}Quick Reference
| Task | Pattern |
|---|---|
| Persist domain data | Define output port in application, implement in infrastructure |
| Expose use case | Define input port and service in application |
| Keep domain pure | No annotations, no I/O, no framework imports |
Resources
- Hexagonal Architecture: https://alistair.cockburn.us/hexagonal-architecture/
- Clean Architecture: https://www.oreilly.com/library/view/clean-architecture/9780134494272/
