@Target(TYPE) @Retention(RUNTIME) @Documented @Import(RabbitListenerConfigurationSelector.class) public @interface EnableRabbit

Enable Rabbit listener annotated endpoints that are created under the cover by a RabbitListenerContainerFactory. To be used on Configuration classes as follows:

 @Configuration
 @EnableRabbit
 public class AppConfig {
     @Bean
     public SimpleRabbitListenerContainerFactory myRabbitListenerContainerFactory() {
       SimpleRabbitListenerContainerFactory factory = new SimpleRabbitListenerContainerFactory();
       factory.setConnectionFactory(connectionFactory());
       factory.setMaxConcurrentConsumers(5);
       return factory;
     }
     // other @Bean definitions
 }

The RabbitListenerContainerFactory is responsible to create the listener container responsible for a particular endpoint. Typical implementations, as the SimpleRabbitListenerContainerFactory used in the sample above, provides the necessary configuration options that are supported by the underlying MessageListenerContainer.

@EnableRabbit enables detection of RabbitListener annotations on any Spring-managed bean in the container. For example, given a class MyService:

 package com.acme.foo;

 public class MyService {
     @RabbitListener(containerFactory="myRabbitListenerContainerFactory", queues="myQueue")
     public void process(String msg) {
         // process incoming message
     }
 }

The container factory to use is identified by the containerFactory attribute defining the name of the RabbitListenerContainerFactory bean to use. When none is set a RabbitListenerContainerFactory bean with name rabbitListenerContainerFactory is assumed to be present.

the following configuration would ensure that every time a Message is received on the Queue named "myQueue", MyService.process() is called with the content of the message:

 @Configuration
 @EnableRabbit
 public class AppConfig {
     @Bean
     public MyService myService() {
         return new MyService();
     }

     // Rabbit infrastructure setup
 }

Alternatively, if MyService were annotated with @Component, the following configuration would ensure that its @RabbitListener annotated method is invoked with a matching incoming message:

 @Configuration
 @EnableRabbit
 @ComponentScan(basePackages="com.acme.foo")
 public class AppConfig {
 }

Note that the created containers are not registered against the application context but can be easily located for management purposes using the RabbitListenerEndpointRegistry.

Annotated methods can use flexible signature; in particular, it is possible to use the Message abstraction and related annotations, see RabbitListener Javadoc for more details. For instance, the following would inject the content of the message and a a custom "myCounter" AMQP header:

 @RabbitListener(containerFactory = "myRabbitListenerContainerFactory", queues = "myQueue")
 public void process(String msg, @Header("myCounter") int counter) {
     // process incoming message
 }

These features are abstracted by the MessageHandlerMethodFactory that is responsible to build the necessary invoker to process the annotated method. By default, DefaultMessageHandlerMethodFactory is used.

When more control is desired, a @Configuration class may implement RabbitListenerConfigurer. This allows access to the underlying RabbitListenerEndpointRegistrar instance. The following example demonstrates how to specify an explicit default RabbitListenerContainerFactory

 @Configuration
 @EnableRabbit
 public class AppConfig implements RabbitListenerConfigurer {
     @Override
     public void configureRabbitListeners(RabbitListenerEndpointRegistrar registrar) {
         registrar.setContainerFactory(myRabbitListenerContainerFactory());
     }

     @Bean
     public RabbitListenerContainerFactory<?> myRabbitListenerContainerFactory() {
         // factory settings
     }

     @Bean
     public MyService myService() {
         return new MyService();
     }
 }

For reference, the example above can be compared to the following Spring XML configuration:

 <beans>
     <rabbit:annotation-driven container-factory="myRabbitListenerContainerFactory"/>

     <bean id="myRabbitListenerContainerFactory"
           class="org.springframework.amqp.rabbit.config.SimpleRabbitListenerContainerFactory">
           // factory settings
     </bean>

     <bean id="myService" class="com.acme.foo.MyService"/>
 </beans>

It is also possible to specify a custom RabbitListenerEndpointRegistry in case you need more control on the way the containers are created and managed. The example below also demonstrates how to customize the RabbitHandlerMethodFactory to use with a custom Validator so that payloads annotated with Validated are first validated against a custom Validator.

 @Configuration
 @EnableRabbit
 public class AppConfig implements RabbitListenerConfigurer {
     @Override
     public void configureRabbitListeners(RabbitListenerEndpointRegistrar registrar) {
         registrar.setEndpointRegistry(myRabbitListenerEndpointRegistry());
         registrar.setMessageHandlerMethodFactory(myMessageHandlerMethodFactory());
     }

     @Bean
     public RabbitListenerEndpointRegistry<?> myRabbitListenerEndpointRegistry() {
         // registry configuration
     }

     @Bean
     public RabbitHandlerMethodFactory myMessageHandlerMethodFactory() {
        DefaultRabbitHandlerMethodFactory factory = new DefaultRabbitHandlerMethodFactory();
        factory.setValidator(new MyValidator());
        return factory;
     }

     @Bean
     public MyService myService() {
         return new MyService();
     }
 }

For reference, the example above can be compared to the following Spring XML configuration:

 <beans>
     <rabbit:annotation-driven registry="myRabbitListenerEndpointRegistry"
         handler-method-factory="myRabbitHandlerMethodFactory"/>

     <bean id="myRabbitListenerEndpointRegistry"
           class="org.springframework.amqp.rabbit.config.RabbitListenerEndpointRegistry">
           // registry configuration
     </bean>

     <bean id="myRabbitHandlerMethodFactory"
           class="org.springframework.amqp.rabbit.config.DefaultRabbitHandlerMethodFactory">
         <property name="validator" ref="myValidator"/>
     </bean>

     <bean id="myService" class="com.acme.foo.MyService"/>
 </beans>

Implementing RabbitListenerConfigurer also allows for fine-grained control over endpoints registration via the RabbitListenerEndpointRegistrar. For example, the following configures an extra endpoint:

 @Configuration
 @EnableRabbit
 public class AppConfig implements RabbitListenerConfigurer {
     @Override
     public void configureRabbitListeners(RabbitListenerEndpointRegistrar registrar) {
         SimpleRabbitListenerEndpoint myEndpoint = new SimpleRabbitListenerEndpoint();
         // ... configure the endpoint
         registrar.registerEndpoint(endpoint, anotherRabbitListenerContainerFactory());
     }

     @Bean
     public MyService myService() {
         return new MyService();
     }

     @Bean
     public RabbitListenerContainerFactory<?> anotherRabbitListenerContainerFactory() {
         // ...
     }

     // Rabbit infrastructure setup
 }

Note that all beans implementing RabbitListenerConfigurer will be detected and invoked in a similar fashion. The example above can be translated in a regular bean definition registered in the context in case you use the XML configuration.

Since:

1.4

Author:

Stephane Nicoll, Artem Bilan

See Also:

Annotation Interface EnableRabbit