java – Spring – mongodb – aggregation – ‘cursor

执行以下聚合管道：

public void getMostLikedItems () {
        UnwindOperation unwind = Aggregation.unwind("favoriteItems");
        GroupOperation group = Aggregation.group("favoriteItems").count().as("likes");
        SortOperation sort = Aggregation.sort(Sort.Direction.DESC,"likes");

        Aggregation aggregation = newAggregation(unwind,group,sort);
        DBObject result = mongoTemplate.aggregate(aggregation,"users",LikedItem.class).getRawResults();
}

抛出以下异常：

com.mongodb.MongoCommandException: Command failed with error 9: 'The 'cursor' option is required,except for aggregate with the explain argument' on server localhost:27017. The full response is { "ok" : 0.0,"errmsg" : "The 'cursor' option is required,except for aggregate with the explain argument","code" : 9,"codeName" : "FailedToParse" }

我不明白这里的光标选项是什么意思.应该在哪里配置此选项？

编辑这是一个示例用户文档

{
  "_id": "5a6df13552f42a34dcca9aa6","username": "user1","password": "$2a$10$p0OXq5PPa41j1e4iPcGZHuWjoKJ983sieS/ovFI.cVX5Whwj21WYi","favoriteItems": [
    {
      "_id": "5a0c6b2dfd3eb67969316d6d","name": "item1","city": "Rabat"
    },{
      "_id": "5a0c680afd3eb67969316d0b","name": "item2","city": "Rabat"
    }
  ]
}