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spring-boot-architecture

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Structure Spring Boot 3+ projects with feature packaging and clean layering. Use when structuring Spring Boot 3 projects, defining layers, or applying architecture patterns.

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Source SKILL.md: https://github.com/HoangNguyen0403/agent-skills-standard/blob/HEAD/skills/spring-boot/spring-boot-architecture/SKILL.md

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Spring Boot Architecture Standards

Priority: P0 (CRITICAL)

Organize by Feature

  • Package by Feature: Prefer com.app.feature (e.g., user, order) over technical layers (controllers) for scalability.
  • Dependency Rule: Outer layers (Web) depend on Inner (Service). Inner layers MUST NOT depend on Outer.
  • DTO Pattern: ALWAYS use DTOs for API inputs/outputs. NEVER return @Entity directly.
  • Java Records: Use record for DTOs to ensure immutability (Java 17+).

See implementation examples for Java Record DTOs, controller patterns, and global exception handling.

Define Layer Responsibilities

  1. Controller (Web): Handle HTTP, Validation (@Valid), DTO mapping. Delegate logic to Service.
  2. Service (Business): Transaction boundaries, orchestration. Returns Domain/DTOs.
  3. Repository (Data): Database interactions only. Returns Entities/Projections.

Design API Layer

  • Global Error Handling: Use @RestControllerAdvice with ProblemDetails (RFC 7807).
  • Validation: Use Jakarta Bean Validation (@NotNull, @Size) on DTOs.
  • Response: Use ResponseEntity for explicit status or ResponseStatusException.

Verification Checklist (Mandatory)

  • No Entities in API: all API responses using DTOs/Records instead of JPA Entities?
  • Validation: @Valid and Jakarta Bean Validation constraints present on all input DTOs?
  • Layer coupling: Services depend on Controllers? (Prohibited)
  • Transactionality: business transactions correctly bounded with @Transactional in Service layer?
  • Error Details: ProblemDetails used for consistent error responses?

Anti-Patterns

  • No Fat Controllers: Move business logic to Services.
  • No Leaking Entities: Use DTOs instead of JPA Entities in APIs.
  • No Circular Dependencies: Use Events or refactor to decouple services.
  • No God Classes: Split large services into single-responsibility components.

References