java-frameworks

Spring Boot Framework Patterns

Controller Layer

@RestController
@RequestMapping("/api/v1/orders")
@RequiredArgsConstructor
public class OrderController {
    private final OrderService orderService;

    @PostMapping
    @ResponseStatus(HttpStatus.CREATED)
    public OrderResponse createOrder(@Valid @RequestBody CreateOrderRequest request) {
        return orderService.create(request);
    }

    @GetMapping("/{id}")
    public OrderResponse getOrder(@PathVariable Long id) {
        return orderService.findById(id);
    }
}

• Use @RestController, not @Controller + @ResponseBody
• Use @RequiredArgsConstructor (Lombok) for constructor injection
• Use @Valid for request validation
• Return domain DTOs, not entities

Service Layer

@Service
@RequiredArgsConstructor
@Transactional(readOnly = true)
public class OrderService {
    private final OrderRepository orderRepository;
    private final EventPublisher eventPublisher;

    @Transactional
    public OrderResponse create(CreateOrderRequest request) {
        var order = Order.create(request.customerId(), request.items());
        orderRepository.save(order);
        eventPublisher.publish(new OrderCreatedEvent(order.getId()));
        return OrderResponse.from(order);
    }
}

• @Transactional(readOnly = true) at class level, @Transactional on writes
• Business logic in service, not controller

JPA Repository

public interface OrderRepository extends JpaRepository<Order, Long> {
    List<Order> findByCustomerIdAndStatus(String customerId, OrderStatus status);

    @Query("SELECT o FROM Order o WHERE o.createdAt > :since")
    List<Order> findRecentOrders(@Param("since") LocalDateTime since);
}

Configuration

• Use @ConfigurationProperties for typed config, not @Value
• Profile-based: application.yml, application-dev.yml, application-prod.yml
• Secrets via environment variables or vault — never in YAML

Exception Handling

@RestControllerAdvice
public class GlobalExceptionHandler {
    @ExceptionHandler(OrderNotFoundException.class)
    @ResponseStatus(HttpStatus.NOT_FOUND)
    public ProblemDetail handleNotFound(OrderNotFoundException ex) {
        return ProblemDetail.forStatusAndDetail(HttpStatus.NOT_FOUND, ex.getMessage());
    }
}