Spring Cloud Stream with Azure Event Hubs

Article
03/29/2024

This tutorial demonstrates how to send and receive messages using Azure Event Hubs and Spring Cloud Stream Binder Eventhubs in a Spring Boot application.

Prerequisites

An Azure subscription - create one for free.
Java Development Kit (JDK) version 8 or higher.
Apache Maven, version 3.2 or higher.
cURL or a similar HTTP utility to test functionality.
An Azure Event hub. If you don't have one, create an event hub using Azure portal.
An Azure Storage Account for Event hub checkpoints. If you don't have one, create a storage account.
A Spring Boot application. If you don't have one, create a Maven project with the Spring Initializr. Be sure to select Maven Project and, under Dependencies, add the Spring Web and Azure Support dependencies, then select Java version 8 or higher.

Note

To grant your account access to resources, in Azure Event Hubs, assign the Azure Event Hubs Data Receiver and Azure Event Hubs Data Sender role to the Microsoft Entra account you're currently using. Then, in the Azure Storage account, assign the Storage Blob Data Contributor role to the Microsoft Entra account you're currently using. For more information about granting access roles, see Assign Azure roles using the Azure portal and Authorize access to Event Hubs resources using Microsoft Entra ID.

Important

Spring Boot version 2.5 or higher is required to complete the steps in this tutorial.

Send and receive messages from Azure Event Hubs

With an Azure Storage Account and an Azure Event hub, you can send and receive messages using Spring Cloud Azure Stream Binder Event Hubs.

To install the Spring Cloud Azure Stream Binder Event Hubs module, add the following dependencies to your pom.xml file:

The Spring Cloud Azure Bill of Materials (BOM):
```
<dependencyManagement>
  <dependencies>
    <dependency>
      <groupId>com.azure.spring</groupId>
      <artifactId>spring-cloud-azure-dependencies</artifactId>
      <version>5.18.0</version>
      <type>pom</type>
      <scope>import</scope>
    </dependency>
  </dependencies>
</dependencyManagement>
```
Note

If you're using Spring Boot 2.x, be sure to set the spring-cloud-azure-dependencies version to 4.19.0. This Bill of Material (BOM) should be configured in the <dependencyManagement> section of your pom.xml file. This ensures that all Spring Cloud Azure dependencies are using the same version. For more information about the version used for this BOM, see Which Version of Spring Cloud Azure Should I Use.

The Spring Cloud Azure Stream Binder Event Hubs artifact:

<dependency>
   <groupId>com.azure.spring</groupId>
   <artifactId>spring-cloud-azure-stream-binder-eventhubs</artifactId>
</dependency>

Code the application

Use the following steps to configure your application to produce and consume messages using Azure Event Hubs.

Configure the Event hub credentials by adding the following properties to your application.properties file.

 spring.cloud.azure.eventhubs.namespace=${AZURE_EVENTHUBS_NAMESPACE}
 spring.cloud.azure.eventhubs.processor.checkpoint-store.account-name=${AZURE_STORAGE_ACCOUNT_NAME}
 spring.cloud.azure.eventhubs.processor.checkpoint-store.container-name=${AZURE_STORAGE_CONTAINER_NAME}
 spring.cloud.stream.bindings.consume-in-0.destination=${AZURE_EVENTHUB_NAME}
 spring.cloud.stream.bindings.consume-in-0.group=${AZURE_EVENTHUB_CONSUMER_GROUP}
 spring.cloud.stream.bindings.supply-out-0.destination=${AZURE_EVENTHUB_NAME}
 spring.cloud.stream.eventhubs.bindings.consume-in-0.consumer.checkpoint.mode=MANUAL
 spring.cloud.function.definition=consume;supply;
 spring.cloud.stream.poller.initial-delay=0
 spring.cloud.stream.poller.fixed-delay=1000

The following table describes the fields in the configuration:

Field	Description
`spring.cloud.azure.eventhubs.namespace`	Specify the namespace you obtained in your event hub from the Azure portal.
`spring.cloud.azure.eventhubs.processor.checkpoint-store.account-name`	Specify the storage account you created in this tutorial.
`spring.cloud.azure.eventhubs.processor.checkpoint-store.container-name`	Specify the container of your storage account.
`spring.cloud.stream.bindings.consume-in-0.destination`	Specify the event hub you used in this tutorial.
`spring.cloud.stream.bindings.consume-in-0.group`	Specify the Consumer groups in your Event Hubs Instance.
`spring.cloud.stream.bindings.supply-out-0.destination`	Specify the same event hub you used in this tutorial.
`spring.cloud.stream.eventhubs.bindings.consume-in-0.consumer.checkpoint.mode`	Specify `MANUAL`.
`spring.cloud.function.definition`	Specify which functional bean to bind to the external destination(s) exposed by the bindings.
`spring.cloud.stream.poller.initial-delay`	Specify initial delay for periodic triggers. The default value is 0.
`spring.cloud.stream.poller.fixed-delay`	Specify fixed delay for default poller in milliseconds. The default value is 1000 L.

Edit the startup class file to show the following content.

import com.azure.spring.messaging.checkpoint.Checkpointer;
import com.azure.spring.messaging.eventhubs.support.EventHubsHeaders;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.boot.CommandLineRunner;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.annotation.Bean;
import org.springframework.messaging.Message;
import org.springframework.messaging.support.MessageBuilder;
import reactor.core.publisher.Flux;
import reactor.core.publisher.Sinks;
import java.util.function.Consumer;
import java.util.function.Supplier;
import static com.azure.spring.messaging.AzureHeaders.CHECKPOINTER;

@SpringBootApplication
public class EventHubBinderApplication implements CommandLineRunner {

    private static final Logger LOGGER = LoggerFactory.getLogger(EventHubBinderApplication.class);
    private static final Sinks.Many<Message<String>> many = Sinks.many().unicast().onBackpressureBuffer();

    public static void main(String[] args) {
        SpringApplication.run(EventHubBinderApplication.class, args);
    }

    @Bean
    public Supplier<Flux<Message<String>>> supply() {
        return ()->many.asFlux()
                       .doOnNext(m->LOGGER.info("Manually sending message {}", m))
                       .doOnError(t->LOGGER.error("Error encountered", t));
    }

    @Bean
    public Consumer<Message<String>> consume() {
        return message->{
            Checkpointer checkpointer = (Checkpointer) message.getHeaders().get(CHECKPOINTER);
            LOGGER.info("New message received: '{}', partition key: {}, sequence number: {}, offset: {}, enqueued "
                    +"time: {}",
                message.getPayload(),
                message.getHeaders().get(EventHubsHeaders.PARTITION_KEY),
                message.getHeaders().get(EventHubsHeaders.SEQUENCE_NUMBER),
                message.getHeaders().get(EventHubsHeaders.OFFSET),
                message.getHeaders().get(EventHubsHeaders.ENQUEUED_TIME)
            );
            checkpointer.success()
                        .doOnSuccess(success->LOGGER.info("Message '{}' successfully checkpointed",
                            message.getPayload()))
                        .doOnError(error->LOGGER.error("Exception found", error))
                        .block();
        };
    }

    @Override
    public void run(String... args) {
        LOGGER.info("Going to add message {} to sendMessage.", "Hello World");
        many.emitNext(MessageBuilder.withPayload("Hello World").build(), Sinks.EmitFailureHandler.FAIL_FAST);
    }

}

Tip

In this tutorial, there are no authentication operations in the configurations or the code. However, connecting to Azure services requires authentication. To complete the authentication, you need to use Azure Identity. Spring Cloud Azure uses DefaultAzureCredential, which the Azure Identity library provides to help you get credentials without any code changes.

DefaultAzureCredential supports multiple authentication methods and determines which method to use at runtime. This approach enables your app to use different authentication methods in different environments (such as local and production environments) without implementing environment-specific code. For more information, see DefaultAzureCredential.

To complete the authentication in local development environments, you can use Azure CLI, Visual Studio Code, PowerShell, or other methods. For more information, see Azure authentication in Java development environments. To complete the authentication in Azure hosting environments, we recommend using user-assigned managed identity. For more information, see What are managed identities for Azure resources?

Start the application. Messages like this will be posted in your application log, as shown in the following example output:

New message received: 'Hello World', partition key: 107207233, sequence number: 458, offset: 94256, enqueued time: 2023-02-17T08:27:59.641Z
Message 'Hello World!' successfully checkpointed

Deploy to Azure Spring Apps

Now that you have the Spring Boot application running locally, it's time to move it to production. Azure Spring Apps makes it easy to deploy Spring Boot applications to Azure without any code changes. The service manages the infrastructure of Spring applications so developers can focus on their code. Azure Spring Apps provides lifecycle management using comprehensive monitoring and diagnostics, configuration management, service discovery, CI/CD integration, blue-green deployments, and more. To deploy your application to Azure Spring Apps, see Deploy your first application to Azure Spring Apps.

Next steps

Azure for Spring developers Spring Cloud Azure Stream Binder Event Hubs Samples

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