Error inserting embedded documents into MongoDB using Scala - mongodb

Question

I use mongo-scala-driver 2.9.0 and this is a function saving a user's Recommendation List to MongoDB. The argument streamRecs is An Array of (productId:Int, score:Double). Now i want to insert a document consisting of an useId and its relevant reconmendation list recs. However, there is an error in the line val doc:Document = Document("userId" -> userId,"recs"->recs). Does anyone know what goes wrong?
def saveRecsToMongoDB(userId: Int, streamRecs: Array[(Int, Double)])(implicit mongoConfig: MongoConfig): Unit ={
val streamRecsCollection = ConnHelper.mongoClient.getDatabase(mongoConfig.db).getCollection(STREAM_RECS_COLLECTION)
streamRecsCollection.findOneAndDelete(equal("userId",userId))
val recs: Array[Document] = streamRecs.map(item=>Document("productId"->item._1,"score"->item._2))
val doc:Document = Document("userId" -> userId,"recs"->recs)
streamRecsCollection.insertOne(doc)
}
the document i want to insert into MongoDB is like this(it means an
user and his recommendation products and scores):
{
"_id":****,
"userId":****,
"recs":[
{
"productId":****,
"score":****
},
{
"productId":****,
"score":****
},
{
"productId":****,
"score":****
},
{
"productId":****,
"score":****
}
]
}

Answer 1

When creating a BSON document, declare the Bson type explicitly for each value in the key/value pair, like so:
/* Compose Bson document */
val document = Document(
"email" -> BsonString("email#domain.com"),
"token" -> BsonString("some_random_string"),
"created" -> BsonDateTime(org.joda.time.DateTime.now.toDate)
)
To see an example, please check https://code.linedrop.io/articles/Storing-Object-in-MongoDB.