@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 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

See Also:

Annotation Interface EnableRabbit