# Azure Service Bus client library for Java Microsoft Azure Service Bus is a fully managed enterprise integration message broker. Service Bus can decouple applications and services. Service Bus offers a reliable and secure platform for asynchronous transfer of data and state. Data is transferred between different applications and services using messages. If you would like to know more about Azure Service Bus, you may wish to review: [What is Service Bus][product_docs] The Azure Service Bus client library allows for sending and receiving of Azure Service Bus messages and may be used to: - Transfer business data, such as sales or purchase orders, journals, or inventory movements. - Decouple applications to improve reliability and scalability of applications and services. Clients and services don't have to be online at the same time. - Enable 1:n relationships between publishers and subscribers. - Implement workflows that require message ordering or message deferral. [Source code][source_code] | [API reference documentation][api_documentation] | [Product documentation][product_docs]| [Samples][sample_examples] ## Getting started ### Prerequisites - [Java Development Kit (JDK)][java_development_kit] with version 8 or above - [Maven][maven] - Microsoft Azure subscription - You can create a free account at: [https://azure.microsoft.com](https://azure.microsoft.com) - Azure Service Bus instance - Step-by-step guide for [creating a Service Bus instance using Azure Portal][service_bus_create] To quickly create the needed Service Bus resources in Azure and to receive a connection string for them, you can deploy our sample template by clicking: [![](http://azuredeploy.net/deploybutton.png)](https://portal.azure.com/#create/Microsoft.Template/uri/https%3A%2F%2Fraw.githubusercontent.com%2FAzure%2Fazure-sdk-for-net%2Fmaster%2Fsdk%2Fservicebus%2FAzure.Messaging.ServiceBus%2Fassets%2Fsamples-azure-deploy.json) ### Include the package [//]: # ({x-version-update-start;com.azure:azure-messaging-servicebus;current}) ```xml com.azure azure-messaging-servicebus 7.0.2 ``` [//]: # ({x-version-update-end}) ### Authenticate the client For the Service Bus client library to interact with Service Bus, it will need to understand how to connect and authorize with it. #### Create Service Bus clients using a connection string The easiest means for authenticating is to use a connection string, which automatically created when creating a Service Bus namespace. If you aren't familiar with shared access policies in Azure, you may wish to follow the step-by-step guide to [get a Service Bus connection string][service_bus_connection_string]. Both the asynchronous and synchronous Service Bus sender and receiver clients are instantiated using `ServiceBusClientBuilder`. The snippets below create a synchronous Service Bus sender and an asynchronous receiver, respectively. ```java ServiceBusSenderClient sender = new ServiceBusClientBuilder() .connectionString("<< CONNECTION STRING FOR THE SERVICE BUS NAMESPACE >>") .sender() .queueName("<< QUEUE NAME >>") .buildClient(); ``` ```java ServiceBusReceiverAsyncClient receiver = new ServiceBusClientBuilder() .connectionString("<< CONNECTION STRING FOR THE SERVICE BUS NAMESPACE >>") .receiver() .topicName("<< TOPIC NAME >>") .subscriptionName("<< SUBSCRIPTION NAME >>") .buildAsyncClient(); ``` #### Create a Service Bus client using Microsoft Identity platform (formerly Azure Active Directory) Azure SDK for Java supports the Azure Identity package, making it simple to get credentials from the Microsoft identity platform. First, add the package: [//]: # ({x-version-update-start;com.azure:azure-identity;dependency}) ```xml com.azure azure-identity 1.2.3 ``` [//]: # ({x-version-update-end}) - Known Issue: The pom.xml file should list `azure-messaging-servicebus` before `azure-identity` client libraries. This issue is resolved with `azure-identity:1.2.1`. Check [here][known-issue-binarydata-notfound] for more details. The implemented ways to request a credential are under the `com.azure.identity.credential` package. The sample below shows how to use an Azure Active Directory (AAD) application client secret to authorize with Azure Service Bus. ##### Authorizing with DefaultAzureCredential Authorization is easiest using [DefaultAzureCredential][wiki_identity]. It finds the best credential to use in its running environment. For more information about using Azure Active Directory authorization with Service Bus, please refer to [the associated documentation][aad_authorization]. Use the returned token credential to authenticate the client: ```java TokenCredential credential = new DefaultAzureCredentialBuilder() .build(); ServiceBusReceiverAsyncClient receiver = new ServiceBusClientBuilder() .credential("<>", credential) .receiver() .queueName("<>") .buildAsyncClient(); ``` ## Key concepts You can interact with the primary resource types within a Service Bus Namespace, of which multiple can exist and on which actual message transmission takes place. The namespace often serves as an application container: * A **[queue][queue_concept]** allows for the sending and receiving of messages, ordered first-in-first-out. It is often used for point-to-point communication. * A **[topic][topic_concept]** is better suited to publisher and subscriber scenarios. A topic publishes messages to subscriptions, of which, multiple can exist simultaneously. * A **[subscription][subscription_concept]** receives messages from a topic. Each subscription is independent and receives a copy of the message sent to the topic. ### Service Bus Clients The builder [`ServiceBusClientBuilder`][ServiceBusClientBuilder] is used to create all the Service Bus clients. * **[`ServiceBusSenderClient`][ServiceBusSenderClient]** A synchronous sender responsible for sending [`ServiceBusMessage`][ServiceBusMessage] to specific queue or topic on Azure Service Bus. * **[`ServiceBusSenderAsyncClient`][ServiceBusSenderAsyncClient]** A asynchronous sender responsible for sending [`ServiceBusMessage`][ServiceBusMessage] to specific queue or topic on Azure Service Bus. * **[`ServiceBusReceiverClient`][ServiceBusReceiverClient]** A synchronous receiver responsible for receiving [`ServiceBusMessage`][ServiceBusMessage] from a specific queue or topic on Azure Service Bus. * **[`ServiceBusReceiverAsyncClient`][ServiceBusReceiverAsyncClient]** A asynchronous receiver responsible for receiving [`ServiceBusMessage`][ServiceBusMessage] from a specific queue or topic on Azure Service Bus. ## Examples - [Send messages](#send-messages) - [Receive messages and renew lock](#receive-messages-and-renew-lock) - [Settle messages](#settle-messages) - [Send and receive from session enabled queues or topics](#send-and-receive-from-session-enabled-queues-or-topics) - [Create a dead-letter queue Receiver](#create-a-dead-letter-queue-receiver) ### Send messages You'll need to create an asynchronous [`ServiceBusSenderAsyncClient`][ServiceBusSenderAsyncClient] or a synchronous [`ServiceBusSenderClient`][ServiceBusSenderClient] to send messages. Each sender can send messages to either a queue or a topic. The snippet below creates a synchronous [`ServiceBusSenderClient`][ServiceBusSenderClient] to publish a message to a queue. ```java ServiceBusSenderClient sender = new ServiceBusClientBuilder() .connectionString("<< CONNECTION STRING FOR THE SERVICE BUS NAMESPACE >>") .sender() .queueName("<< QUEUE NAME >>") .buildClient(); List messages = Arrays.asList( new ServiceBusMessage("Hello world").setMessageId("1"), new ServiceBusMessage("Bonjour").setMessageId("2")); sender.sendMessages(messages); // When you are done using the sender, dispose of it. sender.close(); ``` ### Receive messages To receive messages, you will need to create a `ServiceBusProcessorClient` with callbacks for incoming messages and any error that occurs in the process. You can then start and stop the client as required. By default, the `autoComplete` feature is enabled on the processor client which means that after executing your callback for the message, the client will complete the message i.e. remove it from the queue/subscription. If your callback throws an error, then the client will abandon the message i.e. make it available to be received again. You can disable this feature when creating the processor client. ```java // Sample code that processes a single message Consumer processMessage = messageContext -> { try { System.out.println(messageContext.getMessage().getMessageId()); // other message processing code messageContext.complete(); } catch (Exception ex) { messageContext.abandon(); } }; // Sample code that gets called if there's an error Consumer processError = errorContext -> { System.err.println("Error occurred while receiving message: " + errorContext.getException()); }; // create the processor client via the builder and its sub-builder ServiceBusProcessorClient processorClient = new ServiceBusClientBuilder() .connectionString("<< CONNECTION STRING FOR THE SERVICE BUS NAMESPACE >>") .processor() .queueName("<< QUEUE NAME >>") .processMessage(processMessage) .processError(processError) .disableAutoComplete() .buildProcessorClient(); // Starts the processor in the background and returns immediately processorClient.start(); ``` There are four ways of settling messages using the methods on the message context passed to your callback. - Complete - causes the message to be deleted from the queue or topic. - Abandon - releases the receiver's lock on the message allowing for the message to be received by other receivers. - Defer - defers the message from being received by normal means. In order to receive deferred messages, the sequence number of the message needs to be retained. - Dead-letter - moves the message to the [dead-letter queue][deadletterqueue_docs]. This will prevent the message from being received again. In order to receive messages from the dead-letter queue, a receiver scoped to the dead-letter queue is needed. ### Send and receive from session enabled queues or topics > Using sessions requires you to create a session enabled queue or subscription. You can read more about how to > configure this in "[Message sessions][message-sessions]". Azure Service Bus sessions enable joint and ordered handling of unbounded sequences of related messages. Sessions can be used in first in, first out (FIFO) and request-response patterns. Any sender can create a session when submitting messages into a topic or queue by setting the `ServiceBusMessage.setSessionId(String)` property to some application-defined identifier that is unique to the session. Unlike non-session-enabled queues or subscriptions, only a single receiver can read from a session at any time. When a receiver fetches a session, Service Bus locks the session for that receiver, and it has exclusive access to messages in that session. #### Send a message to a session Create a [`ServiceBusSenderClient`][ServiceBusSenderClient] for a session enabled queue or topic subscription. Setting `ServiceBusMessage.setSessionId(String)` on a `ServiceBusMessage` will publish the message to that session. If the session does not exist, it is created. ```java // Setting sessionId publishes that message to a specific session, in this case, "greeting". ServiceBusMessage message = new ServiceBusMessage("Hello world") .setSessionId("greetings"); sender.sendMessage(message); ``` #### Receive messages from a session Receiving messages from sessions is similar to receiving messages from a non session enabled queue or subscription. The difference is in the builder and the class you use. In non-session case, you would use the sub builder `processor()`. In case of sessions, you would use the sub builder `sessionProcessor()`. Both sub builders will create an instance of `ServiceBusProcessorClient` configured to work on a session or a non-session Service Bus entity. In the case of the session processor, you can pass the maximum number of sessions you want the processor to process concurrently as well. ### Create a dead-letter queue Receiver Azure Service Bus queues and topic subscriptions provide a secondary sub-queue, called a dead-letter queue (DLQ). The dead-letter queue doesn't need to be explicitly created and can't be deleted or otherwise managed independent of the main entity. For session enabled or non-session queue or topic subscriptions, the dead-letter receiver can be created the same way as shown below. Learn more about dead-letter queue [here][dead-letter-queue]. ```java ServiceBusReceiverClient receiver = new ServiceBusClientBuilder() .connectionString("<< CONNECTION STRING FOR THE SERVICE BUS NAMESPACE >>") .receiver() // Use this for session or non-session enabled queue or topic/subscriptions .topicName("<< TOPIC NAME >>") .subscriptionName("<< SUBSCRIPTION NAME >>") .subQueue(SubQueue.DEAD_LETTER_QUEUE) .buildClient(); ``` ## Troubleshooting ### Enable client logging Azure SDK for Java offers a consistent logging story to help aid in troubleshooting application errors and expedite their resolution. The logs produced will capture the flow of an application before reaching the terminal state to help locate the root issue. View the [logging][logging] wiki for guidance about enabling logging. ### Enable AMQP transport logging If enabling client logging is not enough to diagnose your issues. You can enable logging to a file in the underlying AMQP library, [Qpid Proton-J][qpid_proton_j_apache]. Qpid Proton-J uses `java.util.logging`. You can enable logging by create a configuration file with the contents below. Or set `proton.trace.level=ALL` and whichever configuration options you want for the `java.util.logging.Handler` implementation. Implementation classes and their options can be found in [Java 8 SDK javadoc][java_8_sdk_javadocs]. To trace the AMQP transport frames, set the environment variable: `PN_TRACE_FRM=1`. #### Sample "logging.properties" file The configuration file below logs trace output from proton-j to the file "proton-trace.log". ``` handlers=java.util.logging.FileHandler .level=OFF proton.trace.level=ALL java.util.logging.FileHandler.level=ALL java.util.logging.FileHandler.pattern=proton-trace.log java.util.logging.FileHandler.formatter=java.util.logging.SimpleFormatter java.util.logging.SimpleFormatter.format=[%1$tF %1$tr] %3$s %4$s: %5$s %n ``` ### Common exceptions #### AMQP exception This is a general exception for AMQP related failures, which includes the AMQP errors as `ErrorCondition` and the context that caused this exception as `AmqpErrorContext`. `isTransient` is a boolean indicating if the exception is a transient error or not. If a transient AMQP exception occurs, the client library retries the operation as many times as the [AmqpRetryOptons][AmqpRetryOptons] allows. Afterwords, the operation fails and an exception is propagated back to the user. [`AmqpErrorCondition`][AmqpErrorCondition] contains error conditions common to the AMQP protocol and used by Azure services. When an AMQP exception is thrown, examining the error condition field can inform developers as to why the AMQP exception occurred and if possible, how to mitigate this exception. A list of all the AMQP exceptions can be found in [OASIS AMQP Version 1.0 Transport Errors][oasis_amqp_v1_error]. The recommended way to solve the specific exception the AMQP exception represents is to follow the [Service Bus Messaging Exceptions][] guidance. ## Next steps Beyond those discussed, the Azure Service Bus client library offers support for many additional scenarios to help take advantage of the full feature set of the Azure Service Bus service. In order to help explore some of these scenarios, the following set of sample is available [here][samples_readme]. ## Contributing If you would like to become an active contributor to this project please refer to our [Contribution Guidelines](https://github.com/Azure/azure-sdk-for-java/blob/master/CONTRIBUTING.md) for more information. [aad_authorization]: https://docs.microsoft.com/azure/service-bus-messaging/authenticate-application [amqp_transport_error]: https://docs.oasis-open.org/amqp/core/v1.0/os/amqp-core-transport-v1.0-os.html#type-amqp-error [AmqpErrorCondition]: https://github.com/Azure/azure-sdk-for-java/blob/master/sdk/core/azure-core-amqp/src/main/java/com/azure/core/amqp/exception/AmqpErrorCondition.java [AmqpRetryOptons]: https://github.com/Azure/azure-sdk-for-java/blob/master/sdk/core/azure-core-amqp/src/main/java/com/azure/core/amqp/AmqpRetryOptions.java [api_documentation]: https://aka.ms/java-docs [dead-letter-queue]: https://docs.microsoft.com/azure/service-bus-messaging/service-bus-dead-letter-queues [deadletterqueue_docs]: https://docs.microsoft.com/azure/service-bus-messaging/service-bus-dead-letter-queues [java_development_kit]: https://docs.microsoft.com/java/azure/jdk/?view=azure-java-stable [java_8_sdk_javadocs]: https://docs.oracle.com/javase/8/docs/api/java/util/logging/package-summary.html [logging]: https://github.com/Azure/azure-sdk-for-java/wiki/Logging-with-Azure-SDK [maven]: https://maven.apache.org/ [message-sessions]: https://docs.microsoft.com/azure/service-bus-messaging/message-sessions [oasis_amqp_v1_error]: https://docs.oasis-open.org/amqp/core/v1.0/os/amqp-core-transport-v1.0-os.html#type-error [oasis_amqp_v1]: http://docs.oasis-open.org/amqp/core/v1.0/os/amqp-core-overview-v1.0-os.html [product_docs]: https://docs.microsoft.com/azure/service-bus-messaging [qpid_proton_j_apache]: https://qpid.apache.org/proton/ [queue_concept]: https://docs.microsoft.com/azure/service-bus-messaging/service-bus-messaging-overview#queues [ReceiveMode]: https://github.com/Azure/azure-sdk-for-java/blob/master/sdk/servicebus/azure-messaging-servicebus/src/main/java/com/azure/messaging/servicebus/models/ReceiveMode.java [RetryOptions]: https://github.com/Azure/azure-sdk-for-java/blob/master/sdk/core/azure-core-amqp/src/main/java/com/azure/core/amqp/AmqpRetryOptions.java [sample_examples]: https://github.com/Azure/azure-sdk-for-java/blob/master/sdk/servicebus/azure-messaging-servicebus/src/samples/java/com/azure/messaging/servicebus/ [samples_readme]: https://github.com/Azure/azure-sdk-for-java/blob/master/sdk/servicebus/azure-messaging-servicebus/src/samples/java/com/azure/messaging/servicebus [service_bus_connection_string]: https://docs.microsoft.com/azure/service-bus-messaging/service-bus-create-namespace-portal#get-the-connection-string [servicebus_create]: https://docs.microsoft.com/azure/service-bus-messaging/service-bus-create-namespace-portal [servicebus_messaging_exceptions]: https://docs.microsoft.com/azure/service-bus-messaging/service-bus-messaging-exceptions [servicebus_roles]: https://docs.microsoft.com/azure/service-bus-messaging/authenticate-application#built-in-rbac-roles-for-azure-service-bus [ServiceBusClientBuilder]: https://github.com/Azure/azure-sdk-for-java/blob/master/sdk/servicebus/azure-messaging-servicebus/src/main/java/com/azure/messaging/servicebus/ServiceBusClientBuilder.java [ServiceBusMessage]: https://github.com/Azure/azure-sdk-for-java/blob/master/sdk/servicebus/azure-messaging-servicebus/src/main/java/com/azure/messaging/servicebus/ServiceBusMessage.java [ServiceBusReceiverAsyncClient]: https://github.com/Azure/azure-sdk-for-java/blob/master/sdk/servicebus/azure-messaging-servicebus/src/main/java/com/azure/messaging/servicebus/ServiceBusReceiverAsyncClient.java [ServiceBusReceiverClient]: https://github.com/Azure/azure-sdk-for-java/blob/master/sdk/servicebus/azure-messaging-servicebus/src/main/java/com/azure/messaging/servicebus/ServiceBusReceiverClient.java [ServiceBusSenderAsyncClient]: https://github.com/Azure/azure-sdk-for-java/blob/master/sdk/servicebus/azure-messaging-servicebus/src/main/java/com/azure/messaging/servicebus/ServiceBusSenderAsyncClient.java [ServiceBusSenderClient]: https://github.com/Azure/azure-sdk-for-java/blob/master/sdk/servicebus/azure-messaging-servicebus/src/main/java/com/azure/messaging/servicebus/ServiceBusSenderClient.java [service_bus_create]: https://docs.microsoft.com/azure/service-bus-messaging/service-bus-create-namespace-portal [source_code]: https://github.com/Azure/azure-sdk-for-java/blob/master/sdk/servicebus/azure-messaging-servicebus/ [subscription_concept]: https://docs.microsoft.com/azure/service-bus-messaging/service-bus-queues-topics-subscriptions#topics-and-subscriptions [topic_concept]: https://docs.microsoft.com/azure/service-bus-messaging/service-bus-messaging-overview#topics [wiki_identity]: https://github.com/Azure/azure-sdk-for-java/wiki/Identity-and-Authentication [known-issue-binarydata-notfound]: https://github.com/Azure/azure-sdk-for-java/blob/master/sdk/servicebus/azure-messaging-servicebus/known-issues.md#can-not-resolve-binarydata-or-noclassdeffounderror-version-700 ![Impressions](https://azure-sdk-impressions.azurewebsites.net/api/impressions/azure-sdk-for-java%2Fsdk%2Fservicebus%2Fazure-messaging-servicebus%2FREADME.png)