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Spring Boot CTO

Claude Code correction guide. Updated January 2026.

Installation (CURRENT - January 2026)

# Spring Boot 3.5.x - requires Java 17+
# Use Spring Initializr: https://start.spring.io
# Or with CLI:
curl https://start.spring.io/starter.tgz \
  -d dependencies=web,data-jpa,postgresql \
  -d type=maven-project -d language=java | tar -xzf -
./mvnw spring-boot:run

Claude's Common Mistakes

  1. Field injection with @Autowired — Use constructor injection; more testable
  2. Missing @Transactional — Required on service methods that write to DB
  3. Catching generic Exception — Handle specific exceptions properly
  4. Using Hibernate 5 patterns — Spring Boot 3 uses Hibernate 6 with breaking changes
  5. Jakarta EE namespace — Spring Boot 3 uses jakarta.*, not javax.*

Correct Patterns (2026)

// Constructor injection (not @Autowired field injection)
@Service
@RequiredArgsConstructor
public class UserService {
    private final UserRepository userRepository;
    private final PasswordEncoder passwordEncoder;

    @Transactional
    public UserResponse createUser(CreateUserRequest request) {
        if (userRepository.existsByEmail(request.email())) {
            throw new ConflictException("Email already registered");
        }

        User user = User.builder()
            .email(request.email())
            .password(passwordEncoder.encode(request.password()))
            .build();

        return UserResponse.from(userRepository.save(user));
    }
}

// Jakarta EE (not javax)
import jakarta.persistence.Entity;
import jakarta.validation.constraints.Email;

// Spring Boot 3 records for DTOs
public record CreateUserRequest(
    @Email String email,
    @NotBlank String password
) {}

Version Gotchas

  • Spring Boot 2→3: Java 17 required, javax.* → jakarta.*
  • Spring Boot 3: Hibernate 6 (stricter HQL parsing, type changes)
  • Spring Boot 3.2 EOL: June 2025
  • Spring Boot 3.4 EOL: End of 2025
  • Observability: Use Micrometer Tracing (not Spring Cloud Sleuth)

What NOT to Do

  • ❌ @Autowired private UserRepository repo; — Use constructor injection
  • ❌ import javax.persistence.*; — Use jakarta.persistence.*
  • ❌ catch (Exception e) { log.error(...) } — Handle specific exceptions
  • ❌ Hibernate 5 query patterns — Update for Hibernate 6 stricter parsing
  • ❌ @Transactional on wrong place — Goes on service layer, not repository

Spring Boot 3 Migration

// javax → jakarta migration
// Old: import javax.persistence.Entity;
// New:
import jakarta.persistence.Entity;

// Hibernate 6 stricter queries
// May need to fix HQL/JPQL that worked in Hibernate 5

Production Configuration

# application.yml
spring:
  jpa:
    open-in-view: false  # Prevent lazy loading issues
  datasource:
    hikari:
      maximum-pool-size: 10
server:
  shutdown: graceful
management:
  endpoints:
    web:
      exposure:
        include: health,info,prometheus