mongo groupby後按時間戳排序

Criteria criteria = new Criteria();
 if (userId != null && userId > 0) {
 criteria.orOperator(Criteria.where("device_id").is(deviceId), Criteria.where("uid").is(userId));
 } else {
 criteria.and("device_id").is(deviceId).and("uid").is(0);
 }
 Aggregation agg = Aggregation.newAggregation(
 Aggregation.match(criteria),
 new GroupOperation(Aggregation.fields("vid")).last("$$ROOT").as("data"),
 Aggregation.project("data.vid", "data.lastmodified"),
 Aggregation.sort(Sort.by(Sort.Direction.DESC, "lastmodified")),
 Aggregation.skip(new Long(start)),
 Aggregation.limit(limit)
 );

AggregationResults<Document> likeVideoAggregationResults = mongoTemplateFacade.getMongoUserVideoTemplate().aggregate(agg, "like_video", Document.class);
List<String> vids = new ArrayList<>();
for (Iterator<Document> iterator = likeVideoAggregationResults.iterator(); iterator.hasNext(); ) {
Document obj = iterator.next();
vids.add((String) obj.get("_id"));
}