Send messages to and receive messages from Azure Service Bus queues (Java)

Article
02/10/2023
6 minutes to read

In this quickstart, you'll create a Java app to send messages to and receive messages from an Azure Service Bus queue.

Note

This quick start provides step-by-step instructions for a simple scenario of sending messages to a Service Bus queue and receiving them. You can find pre-built Java samples for Azure Service Bus in the Azure SDK for Java repository on GitHub.

Tip

If you're working with Azure Service Bus resources in a Spring application, we recommend that you consider Spring Cloud Azure as an alternative. Spring Cloud Azure is an open-source project that provides seamless Spring integration with Azure services. To learn more about Spring Cloud Azure, and to see an example using Service Bus, see Spring Cloud Stream with Azure Service Bus.

Prerequisites

An Azure subscription. To complete this tutorial, you need an Azure account. You can activate your MSDN subscriber benefits or sign up for a free account.
If you don't have a queue to work with, follow steps in the Use Azure portal to create a Service Bus queue article to create a queue. Note down the connection string for your Service Bus namespace and the name of the queue you created.
Install Azure SDK for Java. If you're using Eclipse, you can install the Azure Toolkit for Eclipse that includes the Azure SDK for Java. You can then add the Microsoft Azure Libraries for Java to your project. If you're using IntelliJ, see Install the Azure Toolkit for IntelliJ.

Send messages to a queue

In this section, you'll create a Java console project, and add code to send messages to the queue that you created earlier.

Create a Java console project

Create a Java project using Eclipse or a tool of your choice.

Configure your application to use Service Bus

Add references to Azure Core and Azure Service Bus libraries.

If you are using Eclipse and created a Java console application, convert your Java project to a Maven: right-click the project in the Package Explorer window, select Configure -> Convert to Maven project. Then, add dependencies to these two libraries as shown in the following example.

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
	<modelVersion>4.0.0</modelVersion>
	<groupId>org.myorg.sbusquickstarts</groupId>
	<artifactId>sbustopicqs</artifactId>
	<version>0.0.1-SNAPSHOT</version>
	<build>
    	<sourceDirectory>src</sourceDirectory>
    	<plugins>
      		<plugin>
        		<artifactId>maven-compiler-plugin</artifactId>
        		<version>3.8.1</version>
        		<configuration>
          			<release>15</release>
        		</configuration>
      		</plugin>
		</plugins>
	</build>
	<dependencies>
		<dependency>
    		<groupId>com.azure</groupId>
    		<artifactId>azure-messaging-servicebus</artifactId>
    		<version>7.7.0</version>
		</dependency>
	</dependencies>
</project>

Add code to send messages to the queue

Add the following import statements at the topic of the Java file.

import com.azure.messaging.servicebus.*;

import java.util.concurrent.CountDownLatch;
import java.util.concurrent.TimeUnit;
import java.util.Arrays;
import java.util.List;

In the class, define variables to hold connection string and queue name as shown below:
```
static String connectionString = "<NAMESPACE CONNECTION STRING>";
static String queueName = "<QUEUE NAME>";    
```
Replace <NAMESPACE CONNECTION STRING> with the connection string to your Service Bus namespace. And, replace <QUEUE NAME> with the name of the queue.

Add a method named sendMessage in the class to send one message to the queue.

static void sendMessage()
{
    // create a Service Bus Sender client for the queue 
    ServiceBusSenderClient senderClient = new ServiceBusClientBuilder()
            .connectionString(connectionString)
            .sender()
            .queueName(queueName)
            .buildClient();

    // send one message to the queue
    senderClient.sendMessage(new ServiceBusMessage("Hello, World!"));
    System.out.println("Sent a single message to the queue: " + queueName);        
}

Add a method named createMessages in the class to create a list of messages. Typically, you get these messages from different parts of your application. Here, we create a list of sample messages.

static List<ServiceBusMessage> createMessages()
{
    // create a list of messages and return it to the caller
    ServiceBusMessage[] messages = {
    		new ServiceBusMessage("First message"),
    		new ServiceBusMessage("Second message"),
    		new ServiceBusMessage("Third message")
    };
    return Arrays.asList(messages);
}

Add a method named sendMessageBatch method to send messages to the queue you created. This method creates a ServiceBusSenderClient for the queue, invokes the createMessages method to get the list of messages, prepares one or more batches, and sends the batches to the queue.

static void sendMessageBatch()
{
    // create a Service Bus Sender client for the queue 
    ServiceBusSenderClient senderClient = new ServiceBusClientBuilder()
            .connectionString(connectionString)
            .sender()
            .queueName(queueName)
            .buildClient();

    // Creates an ServiceBusMessageBatch where the ServiceBus.
    ServiceBusMessageBatch messageBatch = senderClient.createMessageBatch();        

	// create a list of messages
    List<ServiceBusMessage> listOfMessages = createMessages();

    // We try to add as many messages as a batch can fit based on the maximum size and send to Service Bus when
    // the batch can hold no more messages. Create a new batch for next set of messages and repeat until all
    // messages are sent.        
    for (ServiceBusMessage message : listOfMessages) {
        if (messageBatch.tryAddMessage(message)) {
            continue;
        }

        // The batch is full, so we create a new batch and send the batch.
        senderClient.sendMessages(messageBatch);
        System.out.println("Sent a batch of messages to the queue: " + queueName);

        // create a new batch
        messageBatch = senderClient.createMessageBatch();

        // Add that message that we couldn't before.
        if (!messageBatch.tryAddMessage(message)) {
            System.err.printf("Message is too large for an empty batch. Skipping. Max size: %s.", messageBatch.getMaxSizeInBytes());
        }
    }

    if (messageBatch.getCount() > 0) {
        senderClient.sendMessages(messageBatch);
        System.out.println("Sent a batch of messages to the queue: " + queueName);
    }

    //close the client
    senderClient.close();
}

Receive messages from a queue

In this section, you'll add code to retrieve messages from the queue.

Add a method named receiveMessages to receive messages from the queue. This method creates a ServiceBusProcessorClient for the queue by specifying a handler for processing messages and another one for handling errors. Then, it starts the processor, waits for few seconds, prints the messages that are received, and then stops and closes the processor.

Important

Replace QueueTest in QueueTest::processMessage in the code with the name of your class.

// handles received messages
static void receiveMessages() throws InterruptedException
{
    CountDownLatch countdownLatch = new CountDownLatch(1);

    // Create an instance of the processor through the ServiceBusClientBuilder
    ServiceBusProcessorClient processorClient = new ServiceBusClientBuilder()
        .connectionString(connectionString)
        .processor()
        .queueName(queueName)
        .processMessage(QueueTest::processMessage)
        .processError(context -> processError(context, countdownLatch))
        .buildProcessorClient();

    System.out.println("Starting the processor");
    processorClient.start();

    TimeUnit.SECONDS.sleep(10);
    System.out.println("Stopping and closing the processor");
    processorClient.close();    	
}

Add the processMessage method to process a message received from the Service Bus subscription.

private static void processMessage(ServiceBusReceivedMessageContext context) {
    ServiceBusReceivedMessage message = context.getMessage();
    System.out.printf("Processing message. Session: %s, Sequence #: %s. Contents: %s%n", message.getMessageId(),
        message.getSequenceNumber(), message.getBody());
}

Add the processError method to handle error messages.

private static void processError(ServiceBusErrorContext context, CountDownLatch countdownLatch) {
    System.out.printf("Error when receiving messages from namespace: '%s'. Entity: '%s'%n",
        context.getFullyQualifiedNamespace(), context.getEntityPath());

    if (!(context.getException() instanceof ServiceBusException)) {
        System.out.printf("Non-ServiceBusException occurred: %s%n", context.getException());
        return;
    }

    ServiceBusException exception = (ServiceBusException) context.getException();
    ServiceBusFailureReason reason = exception.getReason();

    if (reason == ServiceBusFailureReason.MESSAGING_ENTITY_DISABLED
        || reason == ServiceBusFailureReason.MESSAGING_ENTITY_NOT_FOUND
        || reason == ServiceBusFailureReason.UNAUTHORIZED) {
        System.out.printf("An unrecoverable error occurred. Stopping processing with reason %s: %s%n",
            reason, exception.getMessage());

        countdownLatch.countDown();
    } else if (reason == ServiceBusFailureReason.MESSAGE_LOCK_LOST) {
        System.out.printf("Message lock lost for message: %s%n", context.getException());
    } else if (reason == ServiceBusFailureReason.SERVICE_BUSY) {
        try {
            // Choosing an arbitrary amount of time to wait until trying again.
            TimeUnit.SECONDS.sleep(1);
        } catch (InterruptedException e) {
            System.err.println("Unable to sleep for period of time");
        }
    } else {
        System.out.printf("Error source %s, reason %s, message: %s%n", context.getErrorSource(),
            reason, context.getException());
    }
}

Update the main method to invoke sendMessage, sendMessageBatch, and receiveMessages methods and to throw InterruptedException.

public static void main(String[] args) throws InterruptedException {    	
    sendMessage();
	sendMessageBatch();
	receiveMessages();
}

Run the app

When you run the application, you see the following messages in the console window.

Sent a single message to the queue: myqueue
Sent a batch of messages to the queue: myqueue
Starting the processor
Processing message. Session: 88d961dd801f449e9c3e0f8a5393a527, Sequence #: 1. Contents: Hello, World!
Processing message. Session: e90c8d9039ce403bbe1d0ec7038033a0, Sequence #: 2. Contents: First message
Processing message. Session: 311a216a560c47d184f9831984e6ac1d, Sequence #: 3. Contents: Second message
Processing message. Session: f9a871be07414baf9505f2c3d466c4ab, Sequence #: 4. Contents: Third message
Stopping and closing the processor

On the Overview page for the Service Bus namespace in the Azure portal, you can see incoming and outgoing message count. You may need to wait for a minute or so and then refresh the page to see the latest values.

Select the queue on this Overview page to navigate to the Service Bus Queue page. You see the incoming and outgoing message count on this page too. You also see other information such as the current size of the queue, maximum size, active message count, and so on.

Next Steps

See the following documentation and samples: