Spring mongodb查询包含嵌套数组的嵌套数组答案

【问题标题】：Spring mongodb query nested array containing nested arraysSpring mongodb查询包含嵌套数组的嵌套数组
【发布时间】：2019-12-10 09:40:06
【问题描述】：

我有这 3 个课

@Document(collection = "Countries")
class CountryDoc
{
    @Id
    lateinit var id : String

    var name : String = ""

    var governorates : ArrayList<Governorate> = ArrayList()

}

class Governorate
{
    var id : String = ""

    var name : String = ""

    var cardinalPoint : CardinalPoint = CardinalPoint.SOUTH_WEST

    var cities : ArrayList<City> = ArrayList()
}

class City
{
    var id : String = ""

    var name : String = ""
}

我想得到一个城市的完整地址，结果一定是这样的

{
  "countryId" : ""
  "countryName" : "",
  "governorateId" : "",
  "governorateName" : "",
  "cardinalPoint" : ""
  "cityId" : "",
  "cityName" : ""
}

我试过这个查询但没有用，我只有国家的信息

    val countryCriteria = Criteria.where("id").`is`(countryId)
    val governorateCriteria = Criteria.where("id").`is`(governorateId)
    val cityCriteria = Criteria.where("id").`is`(cityId)

    val aggregation = Aggregation.newAggregation(
        Aggregation.match(countryCriteria),
        Aggregation.project().and("id").`as`("countryId").and("name").`as`("countryName"),
        Aggregation.unwind("governorates"),
        Aggregation.match(governorateCriteria),
 Aggregation.project().and("name").`as`("governorateName").and("id").`as`("governorateId").and("cardinalPoint").`as`("cardinalPoint")
        Aggregation.unwind("cities"),
        Aggregation.match(cityCriteria)
        Aggregation.project().and("name").`as`("cityName").and("id").`as`("cityId")
    )

val result = mongoDb.aggregate(aggregation, CountryDoc::class.java, Address::class.java).uniqueMappedResult

我不明白为什么这对我不起作用，有人可以帮助我吗？

【问题讨论】：

标签： java mongodb kotlin spring-data

【解决方案1】：

你可以从我在 Mongoshell 上写的这个查询中得到启发：

可以在Mongo playground上测试查询

db.city.aggregate([
  {
    "$match": {
      "_id": "c1"
    }
  },
  {
    "$lookup": {
      "from": "governate",
      "as": "governates",
      "localField": "_id",
      "foreignField": "cities"
    }
  },
  {
    "$project": {
      "governate": {
        $arrayElemAt: [
          "$governates",
          0
        ]
      },
      "cityName": "$name"
    }
  },
  {
    "$lookup": {
      "from": "country",
      "as": "coutries",
      "localField": "governate._id",
      "foreignField": "governates"
    }
  },
  {
    "$project": {
      "country": {
        $arrayElemAt: [
          "$coutries",
          0
        ]
      },
      "cityName": 1,
      "governateName": "$governate.name",
      "governateId": "$governate._id"
    }
  },
  {
    "$project": {
      "_id": 0,
      "cityId": "$_id",
      "countryName": "$country.name",
      "countryId": "$country._id",
      "cityName": 1,
      "governateId": 1,
      "governateName": 1
    }
  }
])

我使用的数据是这样的：

db={
  "country": [
    {
      "_id": "1",
      "name": "country",
      "governates": [
        "g1"
      ]
    }
  ],
  "governate": [
    {
      "_id": "g1",
      "name": "governate",
      "cities": [
        "c1"
      ]
    }
  ],
  "city": [
    {
      "_id": "c1",
      "name": "city"
    }
  ]
}

【讨论】：