JVM Drivers

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Fauna’s open source JVM driver supports languages that run in the Java Virtual Machine. Currently, Java and Scala clients are implemented.

Current stable version

4.3.0

Repository

fauna/faunadb-jvm

Features

Documentation

Javadocs and Scaladocs are hosted on GitHub:

Detailed documentation is available for these languages:

Dependencies

Shared

Java

  • Java 11

Scala

  • Scala 2.11.x

  • Scala 2.12.x

Install

Java

Download from the Maven central repository:

faunadb-java/pom.xml:
  <dependencies>
  ...
  <dependency>
    <groupId>com.faunadb</groupId>
    <artifactId>faunadb-java</artifactId>
    <version>4.3.0</version>
    <scope>compile</scope>
  </dependency>
  ...
</dependencies>

Scala

faunadb-scala/sbt:
libraryDependencies += ("com.faunadb" %% "faunadb-scala" % "4.3.0")

Usage

Java

import com.faunadb.client.FaunaClient;

import static com.faunadb.client.query.Language.*;

/**
 * This example connects to FaunaDB using the secret provided
 * and creates a new database named "my-first-database"
 */
public class Main {
    public static void main(String[] args) throws Exception {

        //Create an admin connection to FaunaDB.
        FaunaClient adminClient =
            FaunaClient.builder()
                .withSecret("put-your-key-secret-here")
                .build();

        adminClient.query(
            CreateDatabase(
                Obj("name", Value("my-first-database"))
            )
        ).get();

        adminClient.close();
    }
}

For more usage details, see the supplemental Java driver documentation.

Scala

import faunadb._
import faunadb.query._
import scala.concurrent._
import scala.concurrent.duration._

/**
  * This example connects to FaunaDB using the secret provided
  * and creates a new database named "my-first-database"
  */
object Main extends App {

  import ExecutionContext.Implicits._

  val client = FaunaClient(
    secret = "put-your-secret-here"
  )

  val result = client.query(
    CreateDatabase(
      Obj("name" -> "my-first-database")
    )
  )

  Await.result(result, Duration.Inf)

  client.close()
}

For more usage details, see the supplemental Scala driver documentation.

Document streaming

Fauna supports document streaming, where changes to a streamed document are pushed to all clients subscribing to that document.

Java

The streaming API is built using the java.util.concurrent.Flow API, which enables users to establish flow-controlled components in which Publishers produce items consumed by one or more Subscribers, each managed by a Subscription.

The following examples assume that you have already created a FaunaClient. In the example, we are capturing the 4 first messages by manually binding a Subscriber.

// docRef is a reference to the document for which we want to stream
// updates. You can acquire a document reference with a query like the
// following, but it needs to work with the documents that you have.
// Value docRef = Ref(Collection("scoreboards"), "123")

Flow.Publisher<Value> valuePublisher = adminClient.stream(createdDoc).get();
CompletableFuture<List<Value>> capturedEvents = new CompletableFuture<>();

Flow.Subscriber<Value> valueSubscriber = new Flow.Subscriber<>() {
  Flow.Subscription subscription = null;
  ArrayList<Value> captured = new ArrayList<>();
  @Override
  public void onSubscribe(Flow.Subscription s) {
    subscription = s;
    subscription.request(1);
  }

  @Override
  public void onNext(Value v) {
    captured.add(v);
    if (captured.size() == 4) {
      capturedEvents.complete(captured);
      subscription.cancel();
    } else {
      subscription.request(1);
    }
  }

  @Override
  public void onError(Throwable throwable) {
     capturedEvents.completeExceptionally(throwable);
  }

  @Override
  public void onComplete() {
      capturedEvents.completeExceptionally(
          new IllegalStateException("not expecting the stream to complete")
      );
  }
};

// subscribe to publisher
valuePublisher.subscribe(valueSubscriber);

// blocking
List<Value> events = capturedEvents.get();

Scala

The following sections provide examples for managing streams with Flow or Monix, and assume that you have already created a FaunaClient.

Flow subscriber

It is possible to use the java.util.concurrent.Flow API directly by binding a Subscriber manually.

In the following example, we are capturing the 4 first messages:

import faunadb._
import faunadb.query._

// docRef is a reference to the document for which we want to stream
// updates. You can acquire a document reference with a query like the
// following, but it needs to work with the documents that you have.
// val docRef = Ref(Collection("scoreboards"), "123")

client.stream(docRef).flatMap { publisher =>
  // Promise to hold the final state
  val capturedEventsP = Promise[List[Value]]

  // Our manual Subscriber
  val valueSubscriber = new Flow.Subscriber[Value] {
    var subscription: Flow.Subscription = null
    val captured = new ConcurrentLinkedQueue[Value]

    override def onSubscribe(s: Flow.Subscription): Unit = {
      subscription = s
      subscription.request(1)
    }

    override def onNext(v: Value): Unit = {
      captured.add(v)
      if (captured.size() == 4) {
        capturedEventsP.success(captured.iterator().asScala.toList)
        subscription.cancel()
      } else {
        subscription.request(1)
      }
    }

    override def onError(t: Throwable): Unit =
      capturedEventsP.failure(t)

    override def onComplete(): Unit =
      capturedEventsP.failure(
        new IllegalStateException("not expecting the stream to complete")
      )
  }
  // subscribe to publisher
  publisher.subscribe(valueSubscriber)
  // wait for Future completion
  capturedEventsP.future
}

Monix

The reactive-streams standard offers a strong interoperability in the streaming ecosystem.

We can replicate the previous example using the Monix streaming library:

import faunadb._
import faunadb.query._
import monix.execution.Scheduler
import monix.reactive.Observable
import org.reactivestreams.{FlowAdapters, Publisher}

// docRef is a reference to the document for which we want to stream
// updates.  You can acquire a document reference with a query like the
// following, but it needs to work with the documents that you have.
// val docRef = Ref(Collection("scoreboards"), "123")

client.stream(docRef).flatMap { publisher =>
  val reactiveStreamsPublisher: Publisher[Value] = FlowAdapters.toPublisher(
    publisherValue
  )
  Observable.fromReactivePublisher(reactiveStreamsPublisher)
    .take(4) // 4 events
    .toListL
    .runToFuture(Scheduler.Implicits.global)
}

Next steps

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