Spring Boot Best Practices

Spring Boot Code Generation Guidelines

When generating or reviewing Spring Boot code, follow these best practices:

Dependency Injection

• Use constructor injection, never field injection with @Autowired
• Mark injected fields as private final
• Let Lombok's @RequiredArgsConstructor generate constructors when appropriate

// Good
@Service
@RequiredArgsConstructor
public class UserService {
    private final UserRepository userRepository;
    private final EmailService emailService;
}

// Avoid
@Service
public class UserService {
    @Autowired
    private UserRepository userRepository; // Field injection - avoid
}

Package Structure

Follow standard Spring Boot layering:

com.example.project/
├── controller/       # REST endpoints, @RestController
├── service/          # Business logic, @Service
├── repository/       # Data access, extends JpaRepository
├── model/            # JPA entities, @Entity
├── dto/              # Data transfer objects
├── config/           # Configuration classes, @Configuration
└── exception/        # Custom exceptions and @ControllerAdvice

REST Controllers

• Use proper HTTP methods (GET, POST, PUT, DELETE, PATCH)
• Return ResponseEntity<T> for explicit status codes
• Use @Valid for request body validation
• Include API versioning in paths (e.g., /api/v1/users)

@RestController
@RequestMapping("/api/v1/users")
@RequiredArgsConstructor
public class UserController {
    private final UserService userService;

    @GetMapping("/{id}")
    public ResponseEntity<UserDto> getUser(@PathVariable Long id) {
        return userService.findById(id)
            .map(ResponseEntity::ok)
            .orElse(ResponseEntity.notFound().build());
    }

    @PostMapping
    public ResponseEntity<UserDto> createUser(@Valid @RequestBody CreateUserRequest request) {
        UserDto created = userService.create(request);
        return ResponseEntity.status(HttpStatus.CREATED).body(created);
    }
}