Send messages to an Azure Service Bus topic and receive messages from subscriptions to the topic (Java)

In this quickstart, you write Java code using the azure-messaging-servicebus package to send messages to an Azure Service Bus topic and then receive messages from subscriptions to that topic.

Prerequisites

• An Azure subscription. To complete this tutorial, you need an Azure account. You can activate your Visual Studio or MSDN subscriber benefits or sign-up for a free account.
• 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.

Create a namespace in the Azure portal

To begin using Service Bus messaging entities in Azure, you must first create a namespace with a name that is unique across Azure. A namespace provides a scoping container for Service Bus resources (queues, topics, etc.) within your application.

To create a namespace:

1. Sign in to the Azure portal.

2. Navigate to the All services page.

3. On the left navigation bar, select Integration from the list of categories, hover the mouse over Service Bus, and then select + button on the Service Bus tile.

   

4. In the Basics tag of the Create namespace page, follow these steps:

   1. For Subscription, choose an Azure subscription in which to create the namespace.

   2. For Resource group, choose an existing resource group in which the namespace will live, or create a new one.

   3. Enter a name for the namespace. The namespace name should adhere to the following naming conventions:

      • The name must be unique across Azure. The system immediately checks to see if the name is available.
      • The name length is at least 6 and at most 50 characters.
      • The name can contain only letters, numbers, hyphens “-“.
      • The name must start with a letter and end with a letter or number.
      • The name doesn't end with “-sb“ or “-mgmt“.

   4. For Location, choose the region in which your namespace should be hosted.

   5. For Pricing tier, select the pricing tier (Basic, Standard, or Premium) for the namespace. For this quickstart, select Standard.

      Important

      If you want to use topics and subscriptions, choose either Standard or Premium. Topics/subscriptions aren't supported in the Basic pricing tier.

      If you selected the Premium pricing tier, specify the number of messaging units. The premium tier provides resource isolation at the CPU and memory level so that each workload runs in isolation. This resource container is called a messaging unit. A premium namespace has at least one messaging unit. You can select 1, 2, 4, 8 or 16 messaging units for each Service Bus Premium namespace. For more information, see Service Bus Premium Messaging.

   6. Select Review + create at the bottom of the page.

      

   7. On the Review + create page, review settings, and select Create.

5. Once the deployment of the resource is successful, select Go to resource on the deployment page.

   

6. You see the home page for your service bus namespace.

   

Create a topic using the Azure portal

1. On the Service Bus Namespace page, select Topics on the left menu.

2. Select + Topic on the toolbar.

3. Enter a name for the topic. Leave the other options with their default values.

4. Select Create.

   

Create a subscription to the topic

1. Select the topic that you created in the previous section.

   

2. On the Service Bus Topic page, select + Subscription on the toolbar.

   

3. On the Create subscription page, follow these steps:

   1. Enter S1 for name of the subscription.

   2. Enter 3 for Max delivery count.

   3. Then, select Create to create the subscription.

      

Authenticate the app to Azure

This quick start shows you two ways of connecting to Azure Service Bus: passwordless and connection string.

The first option shows you how to use your security principal in Microsoft Entra ID and role-based access control (RBAC) to connect to a Service Bus namespace. You don't need to worry about having hard-coded connection string in your code or in a configuration file or in a secure storage like Azure Key Vault.

The second option shows you how to use a connection string to connect to a Service Bus namespace. If you are new to Azure, you may find the connection string option easier to follow. We recommend using the passwordless option in real-world applications and production environments. For more information, see Authentication and authorization. You can also read more about passwordless authentication on the overview page.

Send messages to a topic

In this section, you create a Java console project, and add code to send messages to the topic you created.

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're 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.

    <dependencies>
        <dependency>
            <groupId>com.azure</groupId>
            <artifactId>azure-messaging-servicebus</artifactId>
            <version>7.13.3</version>
        </dependency>
        <dependency>
            <groupId>com.azure</groupId>
            <artifactId>azure-identity</artifactId>
            <version>1.8.0</version>
            <scope>compile</scope>
        </dependency>
    </dependencies>

        <dependency>
            <groupId>com.azure</groupId>
            <artifactId>azure-messaging-servicebus</artifactId>
            <version>7.13.3</version>
        </dependency>

Add code to send messages to the topic

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

   • Passwordless (Recommended)
   • Connection String

   import com.azure.messaging.servicebus.*;
   import com.azure.identity.*;
   
   import java.util.concurrent.TimeUnit;
   import java.util.Arrays;
   import java.util.List;
   

2. In the class, define variables to hold connection string (not needed for passwordless scenario), topic name, and subscription name.

   • Passwordless (Recommended)
   • Connection String

   static String topicName = "<TOPIC NAME>";
   static String subName = "<SUBSCRIPTION NAME>";
   

   Important

   Replace <TOPIC NAME> with the name of the topic, and <SUBSCRIPTION NAME> with the name of the topic's subscription.

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

   • Passwordless (Recommended)
   • Connection String

   Important

   Replace NAMESPACENAME with the name of your Service Bus namespace.

   static void sendMessage()
   {
       // create a token using the default Azure credential
       DefaultAzureCredential credential = new DefaultAzureCredentialBuilder()
               .build();
   
       ServiceBusSenderClient senderClient = new ServiceBusClientBuilder()
               .fullyQualifiedNamespace("NAMESPACENAME.servicebus.windows.net")
               .credential(credential)
               .sender()
               .topicName(topicName)
               .buildClient();
   
       // send one message to the topic
       senderClient.sendMessage(new ServiceBusMessage("Hello, World!"));
       System.out.println("Sent a single message to the topic: " + topicName);
   }
   
   

4. 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);
   }
   

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

   • Passwordless (Recommended)
   • Connection String

   Important

   Replace NAMESPACENAME with the name of your Service Bus namespace.

   static void sendMessageBatch()
   {
       // create a token using the default Azure credential
       DefaultAzureCredential credential = new DefaultAzureCredentialBuilder()
               .build();
   
       ServiceBusSenderClient senderClient = new ServiceBusClientBuilder()
               .fullyQualifiedNamespace("NAMESPACENAME.servicebus.windows.net")
               .credential(credential)
               .sender()
               .topicName(topicName)
               .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 topic: " + topicName);
   
           // 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 topic: " + topicName);
       }
   
       //close the client
       senderClient.close();
   }
   

Receive messages from a subscription

In this section, you add code to retrieve messages from a subscription to the topic.

1. Add a method named receiveMessages to receive messages from the subscription. This method creates a ServiceBusProcessorClient for the subscription 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.

   • Passwordless (Recommended)
   • Connection String

   Important

   • Replace NAMESPACENAME with the name of your Service Bus namespace.
   • Replace ServiceBusTopicTest in ServiceBusTopicTest::processMessage in the code with the name of your class.

   // handles received messages
   static void receiveMessages() throws InterruptedException
   {
       DefaultAzureCredential credential = new DefaultAzureCredentialBuilder()
               .build();
   
       // Create an instance of the processor through the ServiceBusClientBuilder
       ServiceBusProcessorClient processorClient = new ServiceBusClientBuilder()
           .fullyQualifiedNamespace("NAMESPACENAME.servicebus.windows.net")
           .credential(credential)
           .processor()
           .topicName(topicName)
           .subscriptionName(subName)
           .processMessage(context -> processMessage(context))
           .processError(context -> processError(context))
           .buildProcessorClient();
   
       System.out.println("Starting the processor");
       processorClient.start();
   
       TimeUnit.SECONDS.sleep(10);
       System.out.println("Stopping and closing the processor");
       processorClient.close();
   }
   

2. 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());
   }
   

3. Add the processError method to handle error messages.

   private static void processError(ServiceBusErrorContext context) {
       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());
       } 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());
       }
   }
   

4. 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

Run the program to see the output similar to the following output:

Sent a single message to the topic: mytopic
Sent a batch of messages to the topic: mytopic
Starting the processor
Processing message. Session: e0102f5fbaf646988a2f4b65f7d32385, Sequence #: 1. Contents: Hello, World!
Processing message. Session: 3e991e232ca248f2bc332caa8034bed9, Sequence #: 2. Contents: First message
Processing message. Session: 56d3a9ea7df446f8a2944ee72cca4ea0, Sequence #: 3. Contents: Second message
Processing message. Session: 7bd3bd3e966a40ebbc9b29b082da14bb, Sequence #: 4. Contents: Third message

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

Switch to the Topics tab in the middle-bottom pane, and select the topic to see the Service Bus Topic page for your topic. On this page, you should see four incoming and four outgoing messages in the Messages chart.

If you comment out the receiveMessages call in the main method and run the app again, on the Service Bus Topic page, you see 8 incoming messages (4 new) but four outgoing messages.

On this page, if you select a subscription, you get to the Service Bus Subscription page. You can see the active message count, dead-letter message count, and more on this page. In this example, there are four active messages that the receiver hasn't received yet.

Next steps

See the following documentation and samples:

• Azure Service Bus client library for Java - Readme
• Samples on GitHub
• Java API reference