Mongo Scala Driver - Can't insert in the database

Question

I'm practicing on a project that needs a database connection, I'm using the Play Framework combine to Scala and MongoDB.

I'm also using Mongo-scala-driver and following the documentation. I wrote the exact same code:

    println("start")

    val mongoClient: MongoClient = MongoClient("mongodb://localhost:27017/Sandbox")

    val database: MongoDatabase = mongoClient.getDatabase("test")

    val collection: MongoCollection[Document] = database.getCollection("test")

    val doc: Document = Document("_id" -> 0, "name" -> "MongoDB", "type" -> "database", "count" -> 1, "info" -> Document("x" -> 203, "y" -> 102))

    collection.insertOne(doc).subscribe(new Observer[Completed] {

      override def onSubscribe(subscription: Subscription): Unit = println("Subscribed")

      override def onNext(result: Completed): Unit = println("Inserted")

      override def onError(e: Throwable): Unit = println("Failed")

      override def onComplete(): Unit = println("Completed")
    })

    mongoClient.close()

    println("end")

Nothing is inserted into the database and the only result i get from the log is this:

start
Subscribed
end

I've been looking on stackoverflow for similar subject but everything I found didn't work for me.

Leonid Artioukhov · Accepted Answer · 2017-12-11T13:44:24.387

2

You try insert document in asyncronous mode. Therefore you must define three call back function onNext onError and onComplete But you don't give time for execute insertion.

Try append any timeout before close connection. For example simple add

Thread.sleep(1000)

before

mongoClient.close()

And you no need redefine onSubscribe()

if you not want manually control demand when you move in documents list from you requests then you no need override onSubscribe(). The default definition for onSubscrime() very usable for trivial requests. In you case you no need override him.

The next code is worked

println("start")
val mongoClient: MongoClient = MongoClient("mongodb://DB01-MongoDB:27017/Sandbox")
val database: MongoDatabase = mongoClient.getDatabase("test")
val collection: MongoCollection[Document] = database.getCollection("test")
val doc: Document = Document("_id" -> 0,
                             "name"  -> "MongoDB",
                             "type"  -> "database",
                             "count" -> 1,
                             "info"  -> Document("x" -> 203, "y" -> 102))
collection
  .insertOne(doc)
  .subscribe(new Observer[Completed] {
    override def onNext(result: Completed): Unit = println("Inserted")
    override def onError(e: Throwable): Unit     = println("Failed")
    override def onComplete(): Unit              = println("Completed")
  })

Thread.sleep(1000)
mongoClient.close()
println("end")

}

edited Dec 11 '17 at 13:44

answered Dec 08 '17 at 13:12

Leonid Artioukhov

83
6

Hey thanks for your answer, but still can't make it work ! – Azoulay Jason Dec 08 '17 at 13:26
because you overwrite method onSubscribe. It is used to control demand when iterating an Observable. For more information read here http://mongodb.github.io/mongo-scala-driver/2.1/reference/observables/#back-pressure – Leonid Artioukhov Dec 08 '17 at 13:48
I don't understand, should I overwrite the onSubscribe method or not ? The link you sent me seems to be exactly the same as I did – Azoulay Jason Dec 08 '17 at 14:22
Please help me .. I can't go further – Azoulay Jason Dec 08 '17 at 15:16
I've had a stab at adding some clarification. Let me know if that helps at all! – Leonid Artioukhov Dec 11 '17 at 05:51
Hey thanks again for your help, so i took off the onSubscribe method, but the subscribe method needs to redefine the onSubscribe. – Azoulay Jason Dec 11 '17 at 09:34
Trait Observer already have realisation for onSubscribe method. You don`t have reason for redefine him. – Leonid Artioukhov Dec 11 '17 at 13:42
I tried the exact same code you wrote. Here's the log : `object creation impossible, since method onSubscribe in trait Observer of type (x$1: com.mongodb.async.client.Subscription)Unit is not defined` – Azoulay Jason Dec 11 '17 at 13:55
Check imports need only import org.mongodb.scala._ Which version of database and drivers you use? – Leonid Artioukhov Dec 11 '17 at 15:01
I'm using mongodb 3.4.10 and mongo scala driver 2.1.0 – Azoulay Jason Dec 11 '17 at 15:13
How about imports? – Leonid Artioukhov Dec 11 '17 at 15:20
Let us [continue this discussion in chat](http://chat.stackoverflow.com/rooms/160945/discussion-between-leonid-artioukhov-and-azoulay-jason). – Leonid Artioukhov Dec 11 '17 at 15:22

score 1 · Answer 2 · answered Dec 12 '17 at 16:40

1

The problem was the Observer, I imported it from org.mongodb.async.client but the good one was org.mongodb.scala. Hope this helps someone else.

answered Dec 12 '17 at 16:40

Azoulay Jason

2,787
5
21
46

score 1 · Answer 3 · answered Oct 28 '18 at 10:33

The above solution may work but you might have to trade 1 second every time you insert (or any call). Another solution is to do make use of the call back :

val insertObservable = collection.insertOne(doc)

insertObservable.subscribe(new Observer[Completed] {
    override def onComplete(): Unit = mongoClient.close()
  })

Once the transaction completed, the connection gets closed automatically without wasting 1 second.

Mongo Scala Driver - Can't insert in the database

3 Answers3