regression possibly due to AMQP-807

[fdeguibert]

As asked by @garyrussell, here is the Github issue related to stack overflow https://stackoverflow.com/questions/57927606/spring-amqp-jackson2jsonmessageconverter-setup-typeid-with-interface-instead

The problem

We have upgraded our Spring-boot version from 2.0.5 to 2.1.8.
As a result, Spring AMQP upgraded from 2.0.6 to 2.1.8 also.

Since then Jackson2JsonMessageConverter is unable to parse answer messages coming from methods annotated with @RabbitListener because they return an interface (actually declared as a generic in the code). And this interface is used to set the message _TypeId_ property .

with version 2.0 it used to set TypeId with the actual concrete class.

I did some digging and here is my understanding of the problem (code will follow)

When the method annotated with @RabbitListener returns, the MessagingMessageListenerAdapter#onMessage is invoked and encapsulates the result in a InvocationResult Object, which contains a genericType property.

This genericType is set up from the return type of the method annotated with @RabbitListener.

Then, it is used by the Jackson2JsonMessageConverter#createMessage method to setup _TypeId_ property.

On the other side, the Jackson2JsonMessageConverter#fromMessage can then parse the Json using this propery to find out the actual Type.

The problem is that, since the introduction of InvocationResult and genericType, our method annotated with @RabbitListener is declared as returning an interface and so the _TypeId_ property is set up with the interface instead of the actual concrete class. Here is the bit of code from Jackson2JsonMessageConverter#fromMessage (actualy from AbstractJackson2MessageConverter)which has changed (among other):

if (getClassMapper() == null) {
			getJavaTypeMapper().fromJavaType(this.objectMapper.constructType(
					genericType == null ? objectToConvert.getClass() : genericType), messageProperties);
		}
		else {
			getClassMapper().fromClass(objectToConvert.getClass(), messageProperties); // NOSONAR never null
		}

Since genericType is not null and contains the interfaceType... you can see our trouble.

Prior to version 2.1, we add no problem since the Jackson2JsonMessageConverter#createMessage() was always directly using objectToConvert.getClass():

		if (getClassMapper() == null) {
			getJavaTypeMapper().fromJavaType(this.jsonObjectMapper.constructType(objectToConvert.getClass()),
					messageProperties);

		}
		else {
			getClassMapper().fromClass(objectToConvert.getClass(),
					messageProperties);

		}

The code

Here is our code:

public abstract class AWorker<I extends RequestDtoInterface, O extends ResponseDtoInterface> {
   
    @RabbitListener(queues = "${rabbit.worker.queue}"
            , errorHandler = "workerErrorHandler"
            , returnExceptions = "true")
    public O receiveMessage(I inputMessage, @Header(LoggerUtil.LOGGER_MDC_ID) String mdcId, @Header(RabbitConstants.CONTEXT_INFO_HEADER_KEY) String contextInfoStr) {

       if(inputMessage instanceof RequestDtoFirstImplementation.class){
           return new ResponseDtoFirstImplementation();
       }else{
           return new ResponseDtoSecondImplementation();
       }
    }

}

Of course, the content of receiveMessage method is simplified, the point is that the actual implementation can return differents concretes types depending of the input concrete type