java

Critical Patterns

Constructor Injection (REQUIRED)

// ✅ ALWAYS: Constructor injection for testability
@Service
public class OrderService {
    private final OrderRepository repository;
    private final PaymentService paymentService;
    
    public OrderService(OrderRepository repository, PaymentService paymentService) {
        this.repository = repository;
        this.paymentService = paymentService;
    }
}

// ❌ NEVER: Field injection
@Service