Spring Data रिपॉज़िटरी और क्वेरी विधियाँ

public interface UserRepository extends JpaRepository<User, Long> {
    // Free: findAll, findById, save, delete, count, existsById, etc.
}

public interface UserRepository extends JpaRepository<User, Long> {
    List<User> findByStatus(UserStatus status);
    Optional<User> findByEmail(String email);
    List<User> findByAgeGreaterThanAndStatusOrderByNameAsc(int age, UserStatus s);
    boolean existsByEmail(String email);
    long countByStatus(UserStatus status);
}

List<User> findTop5ByStatusOrderByCreatedAtDesc(UserStatus s);
List<User> findByNameContainingIgnoreCase(String fragment);
List<User> findByCreatedAtBetween(LocalDateTime from, LocalDateTime to);

@Query("SELECT u FROM User u WHERE u.email = :email AND u.status = :status")
Optional<User> findActiveByEmail(@Param("email") String email,
                                @Param("status") UserStatus status);

@Query("SELECT u.name, COUNT(o) FROM User u JOIN u.orders o GROUP BY u.name")
List<Object[]> countOrdersPerUser();

@Query(value = "SELECT * FROM users WHERE tsv @@ plainto_tsquery(:q)",
       nativeQuery = true)
List<User> fullTextSearch(@Param("q") String query);

@Modifying
@Transactional
@Query("UPDATE User u SET u.status = :s WHERE u.lastLogin < :cutoff")
int deactivateInactiveUsers(@Param("s") UserStatus s,
                             @Param("cutoff") LocalDateTime cutoff);

void deleteByStatus(UserStatus status);
long deleteByCreatedAtBefore(LocalDateTime cutoff);

public interface ReadOnlyUserRepository extends PagingAndSortingRepository<User, Long> {
    // Only paging + sorting — no save/delete
}

@EntityGraph(attributePaths = {"orders", "orders.items"})
@Query("SELECT u FROM User u WHERE u.id = :id")
Optional<User> findWithOrders(@Param("id") Long id);

public interface UserRepositoryCustom {
    List<User> searchByCriteria(UserSearchCriteria criteria);
}
public class UserRepositoryCustomImpl implements UserRepositoryCustom {
    @PersistenceContext EntityManager em;
    public List<User> searchByCriteria(UserSearchCriteria c) {
        // use Criteria API or JdbcTemplate
    }
}
public interface UserRepository extends JpaRepository<User,Long>, UserRepositoryCustom {}