add mongo-db dependency and create collection in controller

build.sbt

@@ -21,3 +21,5 @@ libraryDependencies += "ch.qos.logback" % "logback-classic" % "1.2.3"
 libraryDependencies += "com.typesafe.akka" %% "akka-http" % "10.0.0"
 
 libraryDependencies += "com.typesafe.scala-logging" %% "scala-logging" % "3.9.0"
+
+libraryDependencies += "org.mongodb.scala" %% "mongo-scala-driver" % "2.3.0"

src/main/resources/logback.xml

@@ -18,4 +18,6 @@
         <appender-ref ref="STDOUT" />
         <appender-ref ref="FILE" />
     </root>
-</configuration>
+
+    <logger name="org.mongodb.driver" level="INFO" />
+</configuration>

src/main/scala/de/htwg/se/sudoku/controller/controllerComponent/controllerBaseImpl/Controller.scala

@@ -10,8 +10,9 @@ import de.htwg.se.sudoku.model.fileIoComponent.FileIOInterface
 import de.htwg.se.sudoku.model.gridComponent.GridInterface
 import de.htwg.se.sudoku.util.UndoManager
 
-import scala.util.{Success, Failure}
+import scala.util.{Failure, Success}
 import com.typesafe.scalalogging.{LazyLogging, Logger}
+import org.mongodb.scala.{MongoClient, MongoDatabase}
 
 class Controller @Inject()(var grid: GridInterface)
     extends ControllerInterface
@@ -24,6 +25,14 @@ class Controller @Inject()(var grid: GridInterface)
   val injector = Guice.createInjector(new SudokuModule)
   val fileIo = injector.instance[FileIOInterface]
 
+  // database connection (could be injected later if database is running on another server)
+  // connects to the default server localhost on port 27017
+  private val mongoClient: MongoClient = MongoClient()
+  private val db: MongoDatabase = mongoClient.getDatabase("sudoku-in-scala")
+  private val collection = db.getCollection("sudoku-in-scala-col")
+  // uncomment to delete the current database
+  //Await.result(collection.drop().toFuture(), Duration.Inf)
+
   def createEmptyGrid: Unit = {
     grid.size match {
       case 1 => grid = injector.instance[GridInterface](Names.named("tiny"))