Springboot + Hibernate:保存实体时出现重复条目异常

@Transactional
public void saveEntity(Entity entity) {
    if (entityRepository.existsById(entity.getId())) {
        throw new RuntimeException("Entity already exists");
    }
    entityRepository.save(entity);
}

@Entity
public class Entity {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;

    @Version
    private Integer version;

    // other fields and methods
}

@Transactional
public void saveEntity(Entity entity) {
    Entity existingEntity = entityRepository.findById(entity.getId(), LockModeType.PESSIMISTIC_WRITE);
    if (existingEntity != null) {
        throw new RuntimeException("Entity already exists");
    }
    entityRepository.save(entity);
}

@Transactional
public void saveEntity(Entity entity) {
    Session session = entityManager.unwrap(Session.class);
    session.evict(entity); // 清理缓存
    entityRepository.save(entity);
}

@Entity
public class Entity {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;

    @Version
    private Integer version;

    // other fields and methods
}

@Repository
public interface EntityRepository extends JpaRepository<Entity, Long> {
}

@Service
public class EntityService {

    @Autowired
    private EntityRepository entityRepository;

    @Transactional
    public void saveEntity(Entity entity) {
        if (entityRepository.existsById(entity.getId())) {
            throw new RuntimeException("Entity already exists");
        }
        entityRepository.save(entity);
    }
}