layered-architecture

Layered Architecture

Use When

• Generating or modifying Spring Boot controllers, services, repositories, or DTOs
• Spring Boot code generation or refactor where agent defaults would be wrong

Workflow

1. Confirm the change matches this skill's domain triggers before coding.
2. Follow the domain guide conventions and gotchas below — not generic Spring Boot defaults.
3. Apply project-specific response envelopes, DTO boundaries, and dependency injection rules.
4. Validate with targeted tests (slice, integration, or contract as appropriate).
5. Capture evidence before merge: tests, migration notes, or observability proof.

Required Checks

• Constructor injection used; no @Autowired field injection on new code
• Controllers return DTOs/envelopes — never raw JPA entities
• Business logic stays in @Service layer, not controllers or repositories
• Error handling uses project-standard envelope or RFC 9457 ProblemDetail

Domain Guide

Layer Rules

@RestController        ← HTTP only. No business logic. No JPA entities in responses.
      ↓ DTOs
@Service               ← All business logic lives here. Orchestrates repositories.
      ↓ Domain objects / Entities
@Repository            ← Data access only. No business logic. Returns entities or projections.
      ↓ JPA / JDBC
Database

Controller Layer

• Handles HTTP: parsing requests, validating input (@Valid), returning responses
• Calls ONE service method per endpoint — no orchestration in controllers
• Never returns @Entity classes directly — always map to response DTOs
• Never injects @Repository — always goes through a @Service
• Exception handling via @ControllerAdvice, never try/catch in controllers

// ✅ GOOD
@PostMapping("/orders")
public ResponseEntity<OrderResponse> createOrder(@Valid @RequestBody CreateOrderRequest request) {
    Order order = orderService.createOrder(request);
    return ResponseEntity.status(HttpStatus.CREATED).body(OrderResponse.from(order));
}

// ❌ BAD — business logic in controller
@PostMapping("/orders")
public ResponseEntity<Order> createOrder(@RequestBody CreateOrderRequest request) {
    if (request.getItems().isEmpty()) throw new RuntimeException("No items");
    Order order = orderRepository.save(new Order(request)); // direct repo access
    return ResponseEntity.ok(order); // returning entity
}