Setting Up Google Cloud Project and Pub/Sub in Java

Overview

Google Cloud Platform (GCP) provides robust services for building scalable and reliable cloud-based applications. One of these services is Google Cloud Pub/Sub, a messaging service that allows you to send and receive messages between independent applications.

In this blog post, we’ll walk you through the process of setting up a Google Cloud Project and using Google Cloud Pub/Sub in Java. We’ll cover the following steps:

1. Creating a Google Cloud Project
2. Enabling the Pub/Sub API
3. Setting up Authentication
4. Creating a Pub/Sub Topic and Subscription
5. Writing Java Code to Publish and Consume Messages

Let’s get started!

1. Creating a Google Cloud Project

If you don’t have a Google Cloud account, sign up for one at Google Cloud Console. After signing in, create a new project. Give it a unique name and take note of the project ID, as you’ll need it later.

2. Enabling the Pub/Sub API

Once you have your project set up, enable the Google Cloud Pub/Sub API by following these steps:

• Go to the Google Cloud Console.
• Select your project from the dropdown in the upper-left corner.
• Click on the “Navigation menu” (the three horizontal lines) and navigate to “APIs & Services” > “Dashboard.”
• Click the “+ ENABLE APIS AND SERVICES” button.
• Search for “Pub/Sub API” and click on it.
• Click the “Enable” button.

3. Setting up Authentication

To access your Google Cloud resources programmatically, you’ll need to set up authentication. You can create a service account and download the JSON key file to authenticate your Java application.

• In the Google Cloud Console, navigate to “IAM & Admin” > “Service accounts.”
• Create a new service account, giving it a descriptive name and granting it the “Pub/Sub Editor” role.
• After creating the service account, click on it, go to the “Keys” tab, and create a new key. Download the JSON key file and keep it safe.

4. Creating a Pub/Sub Topic and Subscription

In Google Cloud Pub/Sub, messages are published to topics, and subscribers consume messages from subscriptions to those topics. Let’s create a topic and a subscription:

• Go to the Google Cloud Console and navigate to “Pub/Sub” > “Topics.”
• Create a new topic and give it a name.
• After creating the topic, navigate to the “Subscriptions” tab and create a new subscription connected to your topic.

5. Writing Java Code to Publish and Consume Messages

Now that you have your Google Cloud Project, Pub/Sub API enabled, and authentication set up, it’s time to write Java code to interact with Pub/Sub. You’ll need to add the Pub/Sub client library to your project’s dependencies.

Maven Dependency

<dependency>
    <groupId>com.google.cloud</groupId>
    <artifactId>google-cloud-pubsub</artifactId>
    <version>2.5.0</version> <!-- Use the latest version -->
</dependency>

Publish a Message

import com.google.api.core.ApiFuture;
import com.google.cloud.pubsub.v1.Publisher;
import com.google.protobuf.ByteString;
import com.google.pubsub.v1.PubsubMessage;
import com.google.pubsub.v1.TopicName;

public class PubSubPublisher {
    public static void main(String[] args) throws Exception {
        String projectId = "your-project-id";
        String topicId = "your-topic-id";

        TopicName topicName = TopicName.of(projectId, topicId);

        Publisher publisher = Publisher.newBuilder(topicName).build();

        String message = "Hello, Google Cloud Pub/Sub!";
        ByteString data = ByteString.copyFromUtf8(message);

        PubsubMessage pubsubMessage = PubsubMessage.newBuilder().setData(data).build();

        ApiFuture<String> future = publisher.publish(pubsubMessage);
        String messageId = future.get();
        System.out.println("Published message ID: " + messageId);

        publisher.shutdown();
    }
}

Consume Messages

import com.google.api.core.ApiService;
import com.google.cloud.pubsub.v1.*;

public class PubSubSubscriber {
    public static void main(String[] args) throws Exception {
        String projectId = "your-project-id";
        String subscriptionId = "your-subscription-id";

        SubscriptionName subscriptionName = SubscriptionName.of(projectId, subscriptionId);

        MessageReceiver receiver =
            (PubsubMessage message, AckReplyConsumer consumer) -> {
                System.out.println("Received message: " + message.getData().toStringUtf8());
                consumer.ack();
            };

        Subscriber subscriber = Subscriber.newBuilder(subscriptionName, receiver).build();
        subscriber.startAsync().awaitRunning();

        // Keep the program running to continue receiving messages
        subscriber.awaitTerminated();
    }
}

With this above code in place, you can publish and consume messages using Pub/Sub in your Java application.

Conclusion

In conclusion, Google Cloud Pub/Sub is a powerful messaging service that allows you to build distributed and scalable applications in the cloud. By following the steps outlined in this blog post, you can set up a Google Cloud Project and start using Pub/Sub in your Java applications to build robust and reliable message-based systems. I will be covering more topics on log4j in my future blogs, Stay connected. Happy learning 🙂

For more, you can refer to the Pub/Sub documentation: https://cloud.google.com/pubsub/docs/

For a more technical blog, you can refer to the Nashtech blog: https://blog.nashtechglobal.com/