在使用MongoTemplate时，如何将ObjectId类型转换为Long类型？

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-data-mongodb</artifactId>
</dependency>

@Autowired
private MongoTemplate mongoTemplate;

Aggregation aggregation = Aggregation.newAggregation(
    Aggregation.match(Criteria.where("_id").is(new ObjectId(id))),
    Aggregation.project().and(ConvertOperators.ToString.convertToLong("_id")).as("id")
);

AggregationResults<Document> result = mongoTemplate.aggregate(aggregation, "collectionName", Document.class);
List<Document> documents = result.getMappedResults();

Long objectIdAsLong = (Long) documents.get(0).get("id");