Spring Boot Developer Skill

Roadmap Alignment: roadmap.sh/spring-boot Language Reference: Spring Boot Reference Guide

Architecture & Design Patterns

• Layered Architecture: Strictly enforce the Controller -> Service -> Repository pattern.
  • Controllers (@RestController): Handle HTTP requests, validation, and serialization. Should contain NO business logic.
  • Services (@Service): Contain core business logic and transaction management.
  • Repositories (@Repository): Handle database access (usually extending JpaRepository or CrudRepository).
• Dependency Injection: Use Constructor Injection (via Lombok @RequiredArgsConstructor or explicitly writing the constructor). NEVER use field injection (@Autowired on variables) as it makes unit testing difficult and hides dependencies.

Data & Persistence

• Spring Data JPA / Hibernate:
  • Use Entities (@Entity) with proper relationship annotations (@OneToMany, @ManyToOne).
  • Avoid N+1 query problems by using @EntityGraph or custom JPQL JOIN FETCH queries.
  • Keep transaction boundaries at the Service layer using @Transactional.
• Data Transfer Objects (DTOs): Never expose Entities directly via REST controllers. Map Entities to DTOs using libraries like MapStruct or manual mappers.