Google Cloud Pub/Sub Java Client Library

Add the google-cloud-pubsub library to your project using Maven, Gradle, or SBT. It is recommended to use the Google Cloud Libraries BOM (Bill of Materials) to manage dependency versions consistently.

### Maven with BOM

```xml
<dependencyManagement>
  <dependencies>
    <dependency>
      <groupId>com.google.cloud</groupId>
      <artifactId>libraries-bom</artifactId>
      <version>26.76.0</version>
      <type>pom</type>
      <scope>import</scope>
    </dependency>
  </dependencies>
</dependencyManagement>

<dependencies>
  <dependency>
    <groupId>com.google.cloud</groupId>
    <artifactId>google-cloud-pubsub</artifactId>
  </dependency>
</dependencies>

Maven without BOM

<dependency>
  <groupId>com.google.cloud</groupId>
  <artifactId>google-cloud-pubsub</artifactId>
  <version>1.148.0</version>
</dependency>

Gradle 5.x+ with BOM

implementation platform('com.google.cloud:libraries-bom:26.80.0')
implementation 'com.google.cloud:google-cloud-pubsub'

Gradle without BOM

implementation 'com.google.cloud:google-cloud-pubsub:1.150.2'

SBT

libraryDependencies += "com.google.cloud" % "google-cloud-pubsub" % "1.150.2"

Use the Publisher class to send messages to a topic. Publishing is asynchronous and returns an ApiFuture<String> which contains the message ID upon success.

Required imports:

• com.google.api.core.ApiFuture
• com.google.api.core.ApiFutureCallback
• com.google.api.core.ApiFutures
• com.google.cloud.pubsub.v1.Publisher
• com.google.common.util.concurrent.MoreExecutors
• com.google.protobuf.ByteString
• com.google.pubsub.v1.PubsubMessage

Publisher publisher = null;
try {
  publisher = Publisher.newBuilder(topic).build();
  ByteString data = ByteString.copyFromUtf8("my-message");
  PubsubMessage pubsubMessage = PubsubMessage.newBuilder().setData(data).build();
  ApiFuture<String> messageIdFuture = publisher.publish(pubsubMessage);
  ApiFutures.addCallback(messageIdFuture, new ApiFutureCallback<String>() {
    public void onSuccess(String messageId) {
      System.out.println("published with message id: " + messageId);
    }

    public void onFailure(Throwable t) {
      System.out.println("failed to publish: " + t);
    }
  }, MoreExecutors.directExecutor());
  //...
} finally {
  if (publisher != null) {
    publisher.shutdown();
    publisher.awaitTermination(1, TimeUnit.MINUTES);
  }
}

Use the Subscriber class to pull messages from a subscription. You must implement a MessageReceiver to handle incoming messages and call consumer.ack() to acknowledge receipt.

Required imports:

• com.google.cloud.pubsub.v1.AckReplyConsumer
• com.google.cloud.pubsub.v1.MessageReceiver
• com.google.cloud.pubsub.v1.Subscriber
• com.google.common.util.concurrent.MoreExecutors
• com.google.pubsub.v1.PubsubMessage
• com.google.pubsub.v1.SubscriptionName

import com.google.cloud.pubsub.v1.AckReplyConsumer;
import com.google.cloud.pubsub.v1.MessageReceiver;
import com.google.cloud.pubsub.v1.Subscriber;
import com.google.common.util.concurrent.MoreExecutors;
import com.google.pubsub.v1.PubsubMessage;
import com.google.pubsub.v1.SubscriptionName;

SubscriptionName subscription = SubscriptionName.of("test-project", "test-subscription");

MessageReceiver receiver =
  new MessageReceiver() {
    @Override
    public void receiveMessage(PubsubMessage message, AckReplyConsumer consumer) {
      System.out.println("got message: " + message.getData().toStringUtf8());
      consumer.ack();
    }
  };

Subscriber subscriber = null;
try {
  subscriber = Subscriber.newBuilder(subscription.toString(), receiver).build();
  subscriber.addListener(
    new Subscriber.Listener() {
      @Override
      public void failed(Subscriber.State from, Throwable failure) {
        System.err.println(failure);
      }
    },
    MoreExecutors.directExecutor());
  subscriber.startAsync().awaitRunning();
  //...
} finally {
  if (subscriber != null) {
    subscriber.stopAsync();
  }
}