Spring Data MongoTemplate聚合错误'input to$filter must be a array not object'

我的文档结构如下:

{
    "_id" : ObjectId("...."),
    "oneMoreId" : "....",
    "items" : [
            {
                    "itemId" : "...",
                    "type" : "Food",
            }
    ]        
}

在mongodb中运行JSON查询时:

db.inventory.aggregate([
{$match: { $and: [{"oneMoreId":"..."},{"items.type": "Food"}]}},
{"$project": {
"oneMoreId": 1,
"items": {
    "$filter": {
        "input": "$items",
        "as": "item",
        "cond": {
            "$eq": ["$$item.type", "Food"]
        }
    }
}
}}
])

但是,当我使用Spring数据的MongoTemplate运行聚合时,它会让我

$filter的输入必须是数组而不是对象

ProjectionOperation projection = project("oneMoreId").and(new AggregationExpression() {

@Override
public Document toDocument(AggregationOperationContext context) {
    return new Document("$filter", new Document(
                  "input", "$items")
                  .append("as","item")
                  .append("cond", new Document("$eq", Arrays.asList("$$item.type","Food")))
              );
}
}).as("items");

ProjectionOperation projection = project("oneMoreId")
    .and(filter("items")
            .as("item")
            .by(valueOf("item.type")
                    .equalToValue("Food"))).as("items");

任何帮助都将不胜感激。