MongoDB

The MongoDB connector allows you to read and save documents. You can query a stream of documents from MongoSourceMongoSource or update documents in a collection with MongoSinkMongoSink.

This connector is based on the MongoDB Java Driver, which is compatible with MongoDB versions 2.6 through 4.4.

Artifacts

The Akka dependencies are available from Akka’s library repository. To access them there, you need to configure the URL for this repository.

sbt

resolvers += "Akka library repository".at("https://repo.akka.io/maven")

Maven

<project>
  ...
  <repositories>
    <repository>
      <id>akka-repository</id>
      <name>Akka library repository</name>
      <url>https://repo.akka.io/maven</url>
    </repository>
  </repositories>
</project>

Gradle

repositories {
    mavenCentral()
    maven {
        url "https://repo.akka.io/maven"
    }
}

Additionally, add the dependencies as below.

sbt

val AkkaVersion = "2.10.5"
libraryDependencies ++= Seq(
  "com.lightbend.akka" %% "akka-stream-alpakka-mongodb" % "9.0.2",
  "com.typesafe.akka" %% "akka-stream" % AkkaVersion
)

Maven

<properties>
  <akka.version>2.10.5</akka.version>
  <scala.binary.version>2.13</scala.binary.version>
</properties>
<dependencies>
  <dependency>
    <groupId>com.lightbend.akka</groupId>
    <artifactId>akka-stream-alpakka-mongodb_${scala.binary.version}</artifactId>
    <version>9.0.2</version>
  </dependency>
  <dependency>
    <groupId>com.typesafe.akka</groupId>
    <artifactId>akka-stream_${scala.binary.version}</artifactId>
    <version>${akka.version}</version>
  </dependency>
</dependencies>

Gradle

def versions = [
  AkkaVersion: "2.10.5",
  ScalaBinary: "2.13"
]
dependencies {
  implementation "com.lightbend.akka:akka-stream-alpakka-mongodb_${versions.ScalaBinary}:9.0.2"
  implementation "com.typesafe.akka:akka-stream_${versions.ScalaBinary}:${versions.AkkaVersion}"
}

The table below shows direct dependencies of this module and the second tab shows all libraries it depends on transitively.

Direct dependencies

Organization	Artifact	Version
com.typesafe.akka	akka-stream_2.13	2.10.5
org.mongodb.scala	mongo-scala-driver_2.13	4.11.5
org.scala-lang	scala-library	2.13.15

Dependency tree

com.typesafe.akka    akka-stream_2.13    2.10.5    BUSL-1.1
    com.typesafe.akka    akka-actor_2.13    2.10.5    BUSL-1.1
        com.typesafe    config    1.4.3    Apache-2.0
        org.scala-lang    scala-library    2.13.15    Apache-2.0
    com.typesafe.akka    akka-protobuf-v3_2.13    2.10.5    BUSL-1.1
    org.reactivestreams    reactive-streams    1.0.4    MIT-0
    org.scala-lang    scala-library    2.13.15    Apache-2.0
org.mongodb.scala    mongo-scala-driver_2.13    4.11.5    The Apache License, Version 2.0
    org.mongodb.scala    mongo-scala-bson_2.13    4.11.5    The Apache License, Version 2.0
        org.mongodb    bson    4.11.5    The Apache License, Version 2.0
        org.scala-lang    scala-library    2.13.15    Apache-2.0
        org.scala-lang    scala-reflect    2.13.15    Apache-2.0
            org.scala-lang    scala-library    2.13.15    Apache-2.0
    org.mongodb    mongodb-driver-reactivestreams    4.11.5    The Apache License, Version 2.0
        io.projectreactor    reactor-core    3.5.0    Apache License, Version 2.0
            org.reactivestreams    reactive-streams    1.0.4    MIT-0
        org.mongodb    bson    4.11.5    The Apache License, Version 2.0
        org.mongodb    mongodb-driver-core    4.11.5    The Apache License, Version 2.0
            org.mongodb    bson-record-codec    4.11.5    The Apache License, Version 2.0
                org.mongodb    bson    4.11.5    The Apache License, Version 2.0
            org.mongodb    bson    4.11.5    The Apache License, Version 2.0
        org.reactivestreams    reactive-streams    1.0.4    MIT-0
    org.scala-lang    scala-library    2.13.15    Apache-2.0
    org.scala-lang    scala-reflect    2.13.15    Apache-2.0
        org.scala-lang    scala-library    2.13.15    Apache-2.0
org.scala-lang    scala-library    2.13.15    Apache-2.0

Initialization

In the code examples below we will be using Mongo’s support for automatic codec derivation for POJOs. For Scala we will be using a case class and a macro based codec derivation. For Java a codec for POJO is derived using reflection.

Scala

copysourcecase class Number(_id: Int)

Java

copysourcepublic final class Number {
  private Integer _id;

  public Number() {}

  public Number(Integer _id) {
    this._id = _id;
  }

  public void setId(Integer _id) {
    this._id = _id;
  }

  public Integer getId() {
    return _id;
  }

}

For codec support, you first need to setup a CodecRegistry.

Scala

copysourceimport org.bson.codecs.configuration.CodecRegistries.{fromProviders, fromRegistries}
import org.mongodb.scala.MongoClient.DEFAULT_CODEC_REGISTRY
import org.mongodb.scala.bson.codecs.Macros._

val codecRegistry =
  fromRegistries(fromProviders(classOf[Number]), DEFAULT_CODEC_REGISTRY)

Java

copysourcePojoCodecProvider codecProvider = PojoCodecProvider.builder().register(Number.class).build();
CodecRegistry codecRegistry =
    CodecRegistries.fromProviders(codecProvider, new ValueCodecProvider());

Sources provided by this connector need a prepared collection to communicate with the MongoDB server. To get a reference to a collection, let’s initialize a MongoDB connection and access the database.

Scala

copysourceprivate val client = MongoClients.create("mongodb://localhost:27017")
private val db = client.getDatabase("MongoSourceSpec")
private val numbersColl = db
  .getCollection("numbers", classOf[Number])
  .withCodecRegistry(codecRegistry)

Java

copysourceclient = MongoClients.create("mongodb://localhost:27017");
db = client.getDatabase("MongoSourceTest");
numbersColl = db.getCollection("numbers", Number.class).withCodecRegistry(codecRegistry);

We will also need an ActorSystemActorSystem.

Scala

copysourceimplicit val system: ActorSystem = ActorSystem()

Java

copysourcesystem = ActorSystem.create();

Source

Let’s create a source from a Reactive Streams Publisher.

Scala

copysourceval source: Source[Number, NotUsed] =
  MongoSource(numbersColl.find(classOf[Number]))

Java

copysourcefinal Source<Number, NotUsed> source = MongoSource.create(numbersColl.find(Number.class));

And then run it.

Scala

copysourceval rows: Future[Seq[Number]] = source.runWith(Sink.seq)

Java

copysourcefinal CompletionStage<List<Number>> rows = source.runWith(Sink.seq(), system);

Here we used a basic sink to complete the stream by collecting all of the stream elements to a collection. The power of streams comes from building larger data pipelines which leverage backpressure to ensure efficient flow control. Feel free to edit the example code and build more advanced stream topologies.

Flow and Sink

Each of these sink factory methods have a corresponding factory in MongoFlowMongoFlow which will emit the written document or result of the operation downstream.

Insert

We can use a Source of documents to save them to a mongo collection using MongoSink.insertOneMongoSink.insertOne or MongoSink.insertManyMongoSink.insertMany.

Scala

copysourceval testRangeObjects = testRange.map(Number)
val source = Source(testRangeObjects)
source.runWith(MongoSink.insertOne(numbersColl)).futureValue

Java

copysourceList<Number> testRangeObjects = testRange.stream().map(Number::new).collect(toList());
final CompletionStage<Done> completion =
    Source.from(testRangeObjects).runWith(MongoSink.insertOne(numbersColl), system);

Insert Many

Insert many can be used if you have a collection of documents to insert at once.

Scala

copysourceval objects = testRange.map(Number)
val source = Source(objects)
val completion = source.grouped(2).runWith(MongoSink.insertMany[Number](numbersColl))

Java

copysourcefinal List<Number> testRangeObjects = testRange.stream().map(Number::new).collect(toList());
final CompletionStage<Done> completion =
    Source.from(testRangeObjects).grouped(2).runWith(MongoSink.insertMany(numbersColl), system);

Update

We can update documents with a Source of DocumentUpdate which is a filter and an update definition. Use either MongoSink.updateOneMongoSink.updateOne or MongoSink.updateManyMongoSink.updateMany if the filter should target one or many documents.

Scala

copysourceval source = Source(testRange).map(
  i => DocumentUpdate(filter = Filters.eq("value", i), update = Updates.set("updateValue", i * -1))
)
val completion = source.runWith(MongoSink.updateOne(numbersDocumentColl))

Java

copysourcefinal Source<DocumentUpdate, NotUsed> source =
    Source.from(testRange)
        .map(
            i ->
                DocumentUpdate.create(
                    Filters.eq("value", i), Updates.set("updateValue", i * -1)));
final CompletionStage<Done> completion =
    source.runWith(MongoSink.updateOne(numbersDocumentColl), system);

Delete

We can delete documents with a Source of filters. Use either MongoSink.deleteOneMongoSink.deleteOne or MongoSink.deleteManyMongoSink.deleteMany if the filter should target one or many documents.

Scala

copysourceval source = Source(testRange).map(i => Filters.eq("value", i))
val completion = source.runWith(MongoSink.deleteOne(numbersDocumentColl))

Java

copysourcefinal Source<Bson, NotUsed> source = Source.from(testRange).map(i -> Filters.eq("value", i));
final CompletionStage<Done> completion =
    source.runWith(MongoSink.deleteOne(numbersDocumentColl), system);