Mongodb 使用查找、展开和项目获取进行聚合；无法使用构造函数“无参数构造函数”实例化java.util.List；虽然

spring-data-mongodb-3.0.5.RELEASE.jar和mongodb-driver-core-4.0.5.jar

我有以下课程

@Document(collection = "customers")
data class Customer (
    @Id var _id: ObjectId? = null,
    var custId: String? = null,
    var custName: String? = null,
    var accounts: List<Account>? = null
) : Serializable

我在看下面的输出

{ "_id" : ObjectId("5d092132237909001a398cc5"), "custId" : {"123"}, { "custName"  : { "Test"}  }, "accounts" : { "accountId" : {"000079537"} : { "accountType" : "Savings" } } }
{ "_id" : ObjectId("5d092132237909001a398cc5"), "custId" : { "123" },  { "custName" : "Test"  }, "accounts" : { "accountId" : {"000079538"},  {"accountType" : "Current" } } }

在Mongoshell中，下面的脚本给出了上面的输出。但是，当我们使用下面的代码来讨论java时，我们看到了“使用构造函数实例化java.util.List失败，没有带参数的构造函数”，我遵循了这一点，但我们仍然看到了相同的问题

db.getCollection("customers").aggregate([{ "$match" : { "$and" : [{ "custId" : "123"}, ]}},
            { "$lookup" : { "from" : "accounts", "localField" : "custId", "foreignField" : "accounts.custId", "as" : "accounts"}}
           , { "$unwind" : "$accounts"}, { "$project" : {  "custId" : 1, "accounts.accountType" : "$accounts.accountType"}} 

        ]
        )

聚合代码

val unwindOperation = Aggregation.unwind("accounts") 
val lookUp = Aggregation.lookup( lookUpCollectionDetails!!.collection, lookUpCollectionDetails.localField, lookUpCollectionDetails.foreignField, lookUpCollectionDetails.attribute ) 
val limit = Aggregation.limit(mongoResultLimit.toLong()) 
val aggregation = Aggregation.newAggregation( Customer::class.java, match, lookUp, unwindOperation, projectionOperation, limit )

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请共享聚合查询代码。是java还是kotlin？也分享完整的错误我认为错误是告诉你需要一个具有属性和包含particuler属性的构造函数。而且，代码

{“$match”：{“$And”：[{“custId”：“123”}，]}

可以简单地是：``{“$match”：{“custId”：“123”}}`。val unwindoction=Aggregation.unwind（“accounts”）val lookUp=Aggregation.lookUp（lookUpCollectionDetails！！.collection，lookUpCollectionDetails.localField，lookUpCollectionDetails.foreignField，lookUpCollectionDetails.attribute）val limit=Aggregation.limit（mongoResultLimit.toLong（））val Aggregation=Aggregation.newAggregation（Customer:：class.java，匹配，查找，取消操作，ProjectOnOperation，限制）@sidgate-当我删除取消操作时，我看到下面的错误LinkedList无法映射到StringYou未共享

ProjectOnOperation

val unwindOperation = Aggregation.unwind("accounts") 
val lookUp = Aggregation.lookup( lookUpCollectionDetails!!.collection, lookUpCollectionDetails.localField, lookUpCollectionDetails.foreignField, lookUpCollectionDetails.attribute ) 
val limit = Aggregation.limit(mongoResultLimit.toLong()) 
val aggregation = Aggregation.newAggregation( Customer::class.java, match, lookUp, unwindOperation, projectionOperation, limit )