Attach MessageProcessingDecorators to individual Spring Message listeners

[JaidenAshmore]

Currently if a MessageProcessingDecorator is added as a Spring Bean it will be attached to all of the core message listeners. It would be good to be able to define a method to easily attach a decorator to a single listener via an annotation or some other method. For example:

class MessageListeners {

     @QueueListener(...)
     @SomeDecorator
     public void listen() {
              ...
     }
}

[JaidenAshmore]

Release Notes

Currently it is only possible to attach a MessageProcessingDecorator to a core message listener by including it as a Spring bean. This has the disadvantage that it will be applied to all message listeners and therefore it can be desirable to want to apply it to only a subset of listeners. This can be achieved implementing a MessageProcessingDecoratorFactory which will have the opportunity to wrap a message listener, e.g. by looking for an annotation.

Example

1. Implement the factory, for example one that looks for the MyAnnotation

    public class MyDecoratorFactory implements MessageProcessingDecoratorFactory<MyDecorator> {
   
       @Override
       public Optional<MyDecorator> buildDecorator(
           SqsAsyncClient sqsAsyncClient,
           QueueProperties queueProperties,
           String identifier,
           Object bean,
           Method method
       ) {
           return AnnotationUtils
               .findMethodAnnotation(method, MyAnnotation.class)
               .map(annotation -> new MyDecoratorProperties(annotation.value()))
               .map(properties -> new MyDecorator(properties));
        }
   }

2. Add it as a bean in the Spring Context

   @Configuration
   class MyConfiguration {
   
       @Bean
       MyDecoratorFactory myDecoratorFactory() {
           return new MyDecoratorFactory();
       }
    }

3. Apply the annotation to your message listener

    @QueueListener("${insert.queue.url.here}")
    @MyAnnotation("someValue")
    public void processMessage(@Payload final String payload) {
        // process the message payload here
    }