Connect to MongoDB

After retrieving the connection string for your MongoDB Atlas deployment, you can connect to the deployment from your Scala application and query the Atlas sample datasets.

Create an application file

Navigate to the scala-quickstart directory that you made in the Download and Install step of this guide and create the src/main/scala/quickstart nested directories.

Select the tab corresponding to your operating system and run the following commands to create a Main.scala file in the quickstart subdirectory:

cd src/main/scala/quickstart
touch Main.scala

cd src/main/scala/quickstart
type nul > Main.scala

Add helper methods

Add the following Helpers.scala file from the driver source code to the src/main/scala/quickstart directory:

package quickstart
import java.util.concurrent.TimeUnit
import scala.concurrent.Await
import scala.concurrent.duration.Duration
import org.mongodb.scala._
object Helpers {
  implicit class DocumentObservable[C](val observable: Observable[Document]) extends ImplicitObservable[Document] {
    override val converter: (Document) => String = (doc) => doc.toJson
  }
  implicit class GenericObservable[C](val observable: Observable[C]) extends ImplicitObservable[C] {
    override val converter: (C) => String = (doc) => Option(doc).map(_.toString).getOrElse("")
  }
  trait ImplicitObservable[C] {
    val observable: Observable[C]
    val converter: (C) => String
    def results(): Seq[C] = Await.result(observable.toFuture(), Duration(10, TimeUnit.SECONDS))
    def headResult() = Await.result(observable.head(), Duration(10, TimeUnit.SECONDS))
    def printResults(initial: String = ""): Unit = {
      if (initial.length > 0) print(initial)
      results().foreach(res => println(converter(res)))
    }
    def printHeadResult(initial: String = ""): Unit = println(s"${initial}${converter(headResult())}")
  }
}

This file allows you to access helper methods for printing query results.

Add your application code

Copy and paste the following code into the Main.scala file, which queries the movies collection in the sample_mflix database:

package quickstart
import org.mongodb.scala._
import org.mongodb.scala.model.Filters._
import Helpers._
object Main {
  def main(args: Array[String]): Unit = {
    val mongoClient = MongoClient("<connection string>")
    val database: MongoDatabase = 
       mongoClient.getDatabase("sample_mflix")
    val collection: MongoCollection[Document] = 
       database.getCollection("movies")
    val filter = equal("title", "The Shawshank Redemption")
    collection.find(filter).printResults()
    mongoClient.close()
    
  }
}

Assign the connection string

Replace the <connection string> placeholder with the connection string that you copied from the Create a Connection String step of this guide.

Run your Scala application

In your project root directory, run the following commands to start the sbt shell and run your application:

sbt
run

The command line output contains details about the retrieved movie document:

{"_id": {"$oid": "..."}, ... , "genres": ["Crime", "Drama"], "rated": "R",
"metacritic": 80, "title": "The Shawshank Redemption", ... }

If you encounter an error or see no output, ensure that you specified the proper connection string in the Main.scala file and that you loaded the sample data.

Tip

You can exit the sbt shell by running the following command:

exit

After you complete these steps, you have a Scala application that connects to your MongoDB deployment, runs a query on the sample data, and returns a matching document.

Note

If you run into issues on this step, ask for help in the MongoDB Community Forums or submit feedback by using the Rate this page tab on the right or bottom right side of this page.

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Create a Connection String

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