Use the Java Pulsar client with Astra Streaming and Spring

This example demonstrates how you can produce and consume messages with the Java Pulsar client, Astra Streaming, and Spring.

Prerequisites

For this example, you need the following:

JRE 8
Apache Maven™
An Apache Pulsar™ topic in Astra Streaming
A text editor or IDE

Create a Maven project in Spring Initializr

You can use Spring Initializr to quickly create a Java project with the required dependencies, including the Pulsar client dependency.

Go to Spring Initializr to initialize a new project.
Select Maven, Java 17, a non-SNAPSHOT version of Spring Boot, and the Apache Pulsar dependency:
Click Generate Project, download the zip file, and then extract it.

Navigate to src/main/java, and then open the DemoApplication.java file. This file contains the main method that will run your application with the specified dependencies.

DemoApplication.java

package com.example.demo;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.apache.pulsar.client.api.*;
import java.io.IOException;
import java.util.concurrent.TimeUnit;

@SpringBootApplication
public class DemoApplication
{
	private static final String serviceUrl = "<REPLACE_WITH_SERVICE_URL>";
	private static final String pulsarToken = "<REPLACE_WITH_PULSAR_TOKEN>";
	private static final String tenantName = "<REPLACE_WITH_TENANT_NAME>";
	private static final String namespace = "<REPLACE_WITH_NAMESPACE>";
	private static final String topicName = "<REPLACE_WITH_TOPIC>";

	private static final String topic = String.format("persistent://%s/%s/%s", tenantName,namespace,topicName);

	public static void main( String[] args ) throws IOException
	{
		PulsarClient client = PulsarClient.builder()
				.serviceUrl(serviceUrl)
				.authentication(
						AuthenticationFactory.token(pulsarToken)
				)
				.build();

		Producer<String> producer = client.newProducer(Schema.STRING)
				.topic(topic)
				.create();

		producer.send("Hello World");

		producer.close();

		Consumer<String> consumer = client.newConsumer(Schema.STRING)
				.topic(topic)
				.subscriptionName("my-subscription")
				.subscribe();

		boolean receivedMsg = false;

		do {
			// Block for up to 1 second for a message
			Message<String> msg = consumer.receive(1, TimeUnit.SECONDS);

			if(msg != null){
				System.out.printf("Message received: %s", new String(msg.getData()));

				// Acknowledge the message to remove it from the message backlog
				consumer.acknowledge(msg);

				receivedMsg = true;
			}

		} while (!receivedMsg);

		consumer.close();

		client.close();
	}
}

Replace the following values in DemoApplication.java with values from your tenant’s Connect tab in the Astra Portal:

DemoApplication.java

	private static final String serviceUrl = "pulsar+ssl://pulsar-PROVIDER-REGION.streaming.datastax.com:PORT";
	private static final String pulsarToken = "PULSAR_JTW_TOKEN";
	private static final String tenantName = "TENANT_NAME";
	private static final String namespace = "NAMESPACE_NAME";
	private static final String topicName = "TOPIC_NAME";

You can also modify the values in the application.properties file in the /resources directory, which is recommended for production applications. On your tenant’s Connect tab, you can download a properties file with the values your application needs to connect to your Astra Streaming instance. For example:

spring:
    pulsar:
administration:
service-url: https://pulsar-aws-useast1.api.streaming.datastax.com
tls-hostname-verification-enable: true
auth-plugin-class-name: org.apache.pulsar.client.impl.auth.AuthenticationToken
authentication:
token: ***
client:
service-url: pulsar+ssl://pulsar-aws-useast1.streaming.datastax.com:6651
tls-hostname-verification-enable: true
auth-plugin-class-name: org.apache.pulsar.client.impl.auth.AuthenticationToken
authentication:
token: ***

From your project’s root directory, compile the Java application with the Pulsar client dependency:

mvn clean compile

Result

[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESS
[INFO] ------------------------------------------------------------------------
[INFO] Total time:  0.819 s
[INFO] Finished at: 2023-05-09T15:36:33-04:00
[INFO] ------------------------------------------------------------------------

Run the project to send a message to your Astra Streaming cluster:
```
mvn spring-boot:run
```
Result
```
Message received: Hello World
```
In the Astra Portal header, click Applications, and then select Streaming.
Click the name of your tenant, and then verify that the message appears in the specified namespace and topic.

Use the Java Pulsar client with Astra Streaming and Spring

Prerequisites

Create a Maven project in Spring Initializr

See also

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