Injecting beans in Aggregates

Imported from Google Groups
1

Hi all.

I’m writing a prototype to show the capabilities of Event Sourcing and Sagas with Axon, I’m quite new with it. I searched and found this thread [1] in this forum that practically explains my problem, however the solution with [2] is not working. The error I’m having is

UnsupportedHandlerException: On method public TestService(TestStartCommand,org.springframework.web.client.RestTemplate,org.axonframework.commandhandling.gateway.CommandGateway), parameter 2 is invalid. It is not of any format supported by a providedParameterValueResolver.

It’s coming from my JavaConfig class (shameless copy of the quick guide)

@Bean public EventSourcingRepository<TestService> eventRepository() { // we need to configure the repository EventSourcingRepository<AuditService> eventRepository = new EventSourcingRepository<TestService>(TestService.class, eventStore()); eventRepository.setEventBus(eventBus()); // Axon needs to know that our TestService Aggregate can handle commands AggregateAnnotationCommandHandler.subscribe(TestService.class, eventRepository, commandBus()); // <<====== ERROR // Let’s wire the Event Handler in our infrastructure. AnnotationEventListenerAdapter.subscribe(new TestService`Handler(), eventBus());

return eventRepository;
}

`

Following the explanation in [2],

Methods annotated with @CommandHandler and @EventHandler are now inspected by
the SpringBeanParameterResolverFactory, which injects Spring beans as method
parameters. It is automatically enabled when the axon:annotation-support/
element is used. Otherwise, configure the factory is a bean to enable support.

and since I don’t have any XML config, I just added this to my JavaConfig

`
@Bean
public SpringBeanParameterResolverFactory springBeanParameterResolverFactory(){
return new SpringBeanParameterResolverFactory();

}

`

and the constructor of the aggregate is (both restTemplate and commandGateway are defines as beans):

`
@CommandHandler
public TestService (TestStartCommand command, RestTemplate restTemplate, CommandGateway commandGateway) {
this.restTemplate = restTemplate;
this.commandGateway = commandGateway;
this.id = command.getId();
apply(new TestStartedEvent(command.getId(), command.getData()));
}

`

So, it seems that AggregateAnnotationCommandHandler never sees nor uses ``SpringBeanParameterResolverFactory.

Any ideas on what am I doing wrong?

Cheers.

[1] https://groups.google.com/d/msg/axonframework/d9OeCWU2FbQ/dUaHGy5pXj8J
[2] Issues · AxonFramework/AxonFramework · GitHub

2

Well, I solved this particular problem by instead of

// Axon needs to know that our TestService Aggregate can handle commands
AggregateAnnotationCommandHandler.subscribe(TestService.class, eventRepository, commandBus()); // <<====== ERROR

using this instead:

@Bean public AggregateAnnotationCommandHandler<TestService> commandHandler() { CommandTargetResolver commandTargetResolver = new AnnotationCommandTargetResolver(); AggregateAnnotationCommandHandler<TestService> commandHandler = new AggregateAnnotationCommandHandler<TestService>(TestService`.class, eventRepository(), commandTargetResolver, springBeanParameterResolverFactory());
for (String supportedCommand : commandHandler.supportedCommands()) {
commandBus().subscribe(supportedCommand, commandHandler);
}
return commandHandler;
}

`

Now it seems to be working OK, is this the correct way to do it or is there a cleaner way to do it?

Well, problem solved but I’m sure I will have more to ask… :slight_smile:

Cheers.

3

Hi Antonio,

you can also do
AggregateAnnotationCommandHandler.subscribe(TestService.class, eventRepository(), springBeanParameterResolverFactory(), commandTargetResolver);

In that case, you don’t need to do the for loop afterwards.
Cheers,

Allard

PS. Support for easier configuration in JavaConfig is coming up…

4

Hmmm, in Axon 2.2? I can’t see that, only 2 subscribe methods

`

subscribe(Class aggregateType, Repository repository, CommandBus commandBus)

subscribe(Class aggregateType, Repository repository, CommandBus commandBus, CommandTargetResolver commandTargetResolver)

`

none that accepts a ParameterResolverFactory…

5

Sorry, I misread my own interface ;-). Seems like your solution is the easiest one. This definitely needs some api improvement. Coming soon…

Cheers,

Allard

6

I just saw today that v2.3 was released and that

It’s now easier to configure Axon Annotation configuration. Simply put the @AnnotationDriven annotation on your @Configuration bean, and all you @CommandHandler and @EventHandler annotated beans are registered with their respective Bus

However, I tried using this and removing the loop from my code above, but it didn’t work, I had to put the loop back.

Did I misread something?

Cheers.

7

Hi,

the new annotation is about event handler beans, not aggregates. There is no annotation for this yet. That’s the next step.
Did you try using the AggregateAnnotationCommandHandlerFactoryBean? Or alternatively, use a small snippet of xml to define the aggregate-annotation-handler?

Cheers,

Allard

8

Well, I’m using the AggregateAnnotationCommandHandlerFactoryBean now because I no longer need to inject parameters, but to use the SpringBeanParameterResolverFactory that loop is necessary. It should be a question of a couple of lines to implement that inside the AggregateAnnotationCommandHandler itself.

Cheers.