Spring @Repository Exception Translation

Direct Answer

@Repository marks a persistence component as eligible for Spring's exception translation. When a PersistenceExceptionTranslationPostProcessor is configured—as Spring Boot persistence setups commonly do—exceptions from supported persistence technologies can be translated into Spring's DataAccessException hierarchy. The annotation by itself does not rewrite every exception, and errors such as constraint violations still need application-level interpretation.

Code Example

@Repository
public class UserRepository {
    private final JdbcTemplate jdbcTemplate;

    public UserRepository(JdbcTemplate jdbcTemplate) {
        this.jdbcTemplate = jdbcTemplate;
    }

    public void save(User user) {
        // If email already exists, throws SQLException with code 23505 (unique violation)
        jdbcTemplate.update(
            "INSERT INTO users (email, name) VALUES (?, ?)",
            user.email(), user.name()
        );
    }
}

@Service
public class UserService {
    private final UserRepository repository;

    @Transactional
    public void registerUser(User user) {
        try {
            repository.save(user); // Repository throws vendor-specific exception
        } catch (DuplicateKeyException e) { // Service catches Spring's common exception
            throw new BusinessException("Email already registered");
        }
    }
}

Common Mistakes & Pitfalls

• Not using @Repository at all: Freshers sometimes use @Component for data access classes, losing exception translation entirely. When SQLException leaks into the service layer, they're forced to add persistence dependencies.
• Catching generic Exception: Writing catch (Exception e) in the service defeats the purpose because you can't distinguish a duplicate key error from a connection timeout. Use Spring's specific subclasses like DataIntegrityViolationException or OptimisticLockingFailureException.
• Assuming all exceptions are translated: Only exceptions thrown from @Repository beans get translated. If you manually create a DataSource connection outside Spring's management, translation won't happen.