如何在spring data neo4j中更改或删除对象关系的目标？

// 定义节点实体类
@NodeEntity
public class Person {
    @Id
    @GeneratedValue
    private Long id;

    private String name;

    @Relationship(type = "FRIEND")
    private List<Person> friends;

    // 省略构造函数、getter和setter方法
}

// 定义Repository接口
public interface PersonRepository extends Neo4jRepository<Person, Long> {
}

// 在业务逻辑中使用Repository
@Service
public class PersonService {
    @Autowired
    private PersonRepository personRepository;

    public void changeRelationshipTarget(Long sourceId, Long oldTargetId, Long newTargetId) {
        Person source = personRepository.findById(sourceId).orElse(null);
        Person oldTarget = personRepository.findById(oldTargetId).orElse(null);
        Person newTarget = personRepository.findById(newTargetId).orElse(null);

        if (source != null && oldTarget != null && newTarget != null) {
            List<Person> friends = source.getFriends();
            for (Person friend : friends) {
                if (friend.getId().equals(oldTargetId)) {
                    friend = newTarget;
                    break;
                }
            }
            personRepository.save(source);
        }
    }

    public void deleteRelationshipTarget(Long sourceId, Long targetId) {
        Person source = personRepository.findById(sourceId).orElse(null);
        Person target = personRepository.findById(targetId).orElse(null);

        if (source != null && target != null) {
            List<Person> friends = source.getFriends();
            friends.removeIf(friend -> friend.getId().equals(targetId));
            personRepository.save(source);
        }
    }
}