如何将 Scala 案例类转换为 mongo 文档

Question

我想构建一个通用方法来将 Scala 案例类转换为 Mongo 文档。

一个有前途的Document constructor是

fromSeq(ts: Seq[(String, BsonValue)]): Document

我可以将案例类转换为 Map[String -> Any]，但是我丢失了使用隐式转换到 BsonValues 所需的类型信息。也许 TypeTags 可以帮助解决这个问题？

这是我尝试过的：

import org.mongodb.scala.bson.BsonTransformer
import org.mongodb.scala.bson.collection.immutable.Document
import org.mongodb.scala.bson.BsonValue

case class Person(age: Int, name: String) 

//transform scala values into BsonValues
def transform[T](v: T)(implicit transformer: BsonTransformer[T]): BsonValue = transformer(v)

// turn any case class into a Map[String, Any]
def caseClassToMap(cc: Product) = { 
  val values = cc.productIterator
  cc.getClass.getDeclaredFields.map( _.getName -> values.next).toMap
}

// transform a Person into a Document
def personToDocument(person: Person): Document = {  
  val map = caseClassToMap(person)

  val bsonValues = map.toSeq.map { case (key, value) =>
    (key, transform(value))
  }

  Document.fromSeq(bsonValues)
}

<console>:24: error: No bson implicit transformer found for type Any. Implement or import an implicit BsonTransformer for this type.
           (key, transform(value))

Answer 1

def personToDocument(person: Person): Document = {  
    Document("age" -> person.age, "name" -> person.name) 
}

Answer 2

以下代码无需手动转换对象即可工作。

import reactivemongo.api.bson.{BSON, BSONDocument, Macros}

case class Person(name:String = "SomeName", age:Int = 20)

implicit val personHandler = Macros.handler[Person]

val bsonPerson = BSON.writeDocument[Person](Person())

println(s"${BSONDocument.pretty(bsonPerson.getOrElse(BSONDocument.empty))}")

Answer 3

您可以使用 Salat https://github.com/salat/salat。一个很好的例子可以在这里找到 - https://gist.github.com/bhameyie/8276017。这是一段可以帮助你的代码 -

import salat._

val dBObject = grater[Artist].asDBObject(artist)
artistsCollection.save(dBObject, WriteConcern.Safe)

Answer 4

我能够使用 org.bson.BsonDocumentWriter 将案例类序列化为 BsonDocument。下面的代码使用 scala 2.12 和 mongo-scala-driver_2.12 版本 2.6.0 运行

我对这个解决方案的追求得到了这个答案的帮助（他们试图在相反的方向序列化）：Serialize to object using scala mongo driver?

import org.mongodb.scala.bson.codecs.Macros
import org.mongodb.scala.bson.codecs.DEFAULT_CODEC_REGISTRY
import org.bson.codecs.configuration.CodecRegistries.{fromRegistries, fromProviders}
import org.bson.codecs.EncoderContext
import org.bson.BsonDocumentWriter
import org.mongodb.scala.bson.BsonDocument
import org.bson.codecs.configuration.CodecRegistry
import org.bson.codecs.Codec

case class Animal(name : String, species: String, genus: String, weight: Int)

object TempApp {

  def main(args: Array[String]) {

    val jaguar = Animal("Jenny", "Jaguar", "Panthera", 190)

    val codecProvider = Macros.createCodecProvider[Animal]()
    
    val codecRegistry: CodecRegistry = fromRegistries(fromProviders(codecProvider), DEFAULT_CODEC_REGISTRY)

    val codec = Macros.createCodec[Animal](codecRegistry)

    val encoderContext = EncoderContext.builder.isEncodingCollectibleDocument(true).build()

    var doc = BsonDocument()

    val writr = new BsonDocumentWriter(doc) // need to call new since Java lib w/o companion object

    codec.encode(writr, jaguar, encoderContext)

    print(doc)

  }

};