[[messaging.amqp]] == AMQP The Advanced Message Queuing Protocol (AMQP) is a platform-neutral, wire-level protocol for message-oriented middleware. The Spring AMQP project applies core Spring concepts to the development of AMQP-based messaging solutions. Spring Boot offers several conveniences for working with AMQP through RabbitMQ, including the `spring-boot-starter-amqp` "`Starter`". [[messaging.amqp.rabbitmq]] === RabbitMQ support https://www.rabbitmq.com/[RabbitMQ] is a lightweight, reliable, scalable, and portable message broker based on the AMQP protocol. Spring uses `RabbitMQ` to communicate through the AMQP protocol. RabbitMQ configuration is controlled by external configuration properties in `+spring.rabbitmq.*+`. For example, you might declare the following section in `application.properties`: [source,yaml,indent=0,subs="verbatim",configprops,configblocks] ---- spring: rabbitmq: host: "localhost" port: 5672 username: "admin" password: "secret" ---- Alternatively, you could configure the same connection using the `addresses` attribute: [source,yaml,indent=0,subs="verbatim",configprops,configblocks] ---- spring: rabbitmq: addresses: "amqp://admin:secret@localhost" ---- NOTE: When specifying addresses that way, the `host` and `port` properties are ignored. If the address uses the `amqps` protocol, SSL support is enabled automatically. See {spring-boot-autoconfigure-module-code}/amqp/RabbitProperties.java[`RabbitProperties`] for more of the supported property-based configuration options. To configure lower-level details of the RabbitMQ `ConnectionFactory` that is used by Spring AMQP, define a `ConnectionFactoryCustomizer` bean. If a `ConnectionNameStrategy` bean exists in the context, it will be automatically used to name connections created by the auto-configured `CachingConnectionFactory`. TIP: See https://spring.io/blog/2010/06/14/understanding-amqp-the-protocol-used-by-rabbitmq/[Understanding AMQP, the protocol used by RabbitMQ] for more details. [[messaging.amqp.sending]] === Sending a Message Spring's `AmqpTemplate` and `AmqpAdmin` are auto-configured, and you can autowire them directly into your own beans, as shown in the following example: [source,java,indent=0,subs="verbatim"] ---- include::{docs-java}/messaging/amqp/sending/MyBean.java[] ---- NOTE: {spring-amqp-api}/rabbit/core/RabbitMessagingTemplate.html[`RabbitMessagingTemplate`] can be injected in a similar manner. If a `MessageConverter` bean is defined, it is associated automatically to the auto-configured `AmqpTemplate`. If necessary, any `org.springframework.amqp.core.Queue` that is defined as a bean is automatically used to declare a corresponding queue on the RabbitMQ instance. To retry operations, you can enable retries on the `AmqpTemplate` (for example, in the event that the broker connection is lost): [source,yaml,indent=0,subs="verbatim",configprops,configblocks] ---- spring: rabbitmq: template: retry: enabled: true initial-interval: "2s" ---- Retries are disabled by default. You can also customize the `RetryTemplate` programmatically by declaring a `RabbitRetryTemplateCustomizer` bean. If you need to create more `RabbitTemplate` instances or if you want to override the default, Spring Boot provides a `RabbitTemplateConfigurer` bean that you can use to initialize a `RabbitTemplate` with the same settings as the factories used by the auto-configuration. [[messaging.amqp.receiving]] === Receiving a Message When the Rabbit infrastructure is present, any bean can be annotated with `@RabbitListener` to create a listener endpoint. If no `RabbitListenerContainerFactory` has been defined, a default `SimpleRabbitListenerContainerFactory` is automatically configured and you can switch to a direct container using the configprop:spring.rabbitmq.listener.type[] property. If a `MessageConverter` or a `MessageRecoverer` bean is defined, it is automatically associated with the default factory. The following sample component creates a listener endpoint on the `someQueue` queue: [source,java,indent=0,subs="verbatim"] ---- include::{docs-java}/messaging/amqp/receiving/MyBean.java[] ---- TIP: See {spring-amqp-api}/rabbit/annotation/EnableRabbit.html[the Javadoc of `@EnableRabbit`] for more details. If you need to create more `RabbitListenerContainerFactory` instances or if you want to override the default, Spring Boot provides a `SimpleRabbitListenerContainerFactoryConfigurer` and a `DirectRabbitListenerContainerFactoryConfigurer` that you can use to initialize a `SimpleRabbitListenerContainerFactory` and a `DirectRabbitListenerContainerFactory` with the same settings as the factories used by the auto-configuration. TIP: It does not matter which container type you chose. Those two beans are exposed by the auto-configuration. For instance, the following configuration class exposes another factory that uses a specific `MessageConverter`: [source,java,indent=0,subs="verbatim"] ---- include::{docs-java}/messaging/amqp/receiving/custom/MyRabbitConfiguration.java[] ---- Then you can use the factory in any `@RabbitListener`-annotated method, as follows: [source,java,indent=0,subs="verbatim"] ---- include::{docs-java}/messaging/amqp/receiving/custom/MyBean.java[] ---- You can enable retries to handle situations where your listener throws an exception. By default, `RejectAndDontRequeueRecoverer` is used, but you can define a `MessageRecoverer` of your own. When retries are exhausted, the message is rejected and either dropped or routed to a dead-letter exchange if the broker is configured to do so. By default, retries are disabled. You can also customize the `RetryTemplate` programmatically by declaring a `RabbitRetryTemplateCustomizer` bean. IMPORTANT: By default, if retries are disabled and the listener throws an exception, the delivery is retried indefinitely. You can modify this behavior in two ways: Set the `defaultRequeueRejected` property to `false` so that zero re-deliveries are attempted or throw an `AmqpRejectAndDontRequeueException` to signal the message should be rejected. The latter is the mechanism used when retries are enabled and the maximum number of delivery attempts is reached.