Support Spring Beans as parameters in @MessageHandler methods

[frederikb]

I was solving the same requirement for a client of mine when I stumbled upon your work here and gave it a try.

Scenario

• extension version: 0.1.0
• Axon Framework version: 4.10.2
• Description of your use case:

I would like to declare custom Spring beans to be injected in the @MessageHandler event handling methods, e.g.:

@MessageHandler
  protected void apply(
      DomainEvents.MyEvent event, MyBean myBean) {
}

as supported for regular Axon event handlers ( https://docs.axoniq.io/axon-framework-reference/4.10/messaging-concepts/supported-parameters-annotated-handlers/ )

Current Behaviour

This fails with the following exception:

2024-11-05 | 09:47:44.782 | ERROR | http-nio-8080-exec-6 | o.a.c.c.C.[.[.[.[dispatcherServlet] | Servlet.service() for servlet [dispatcherServlet] in context with path [] threw exception [Request processing failed: org.axonframework.test.FixtureExecutionException: No resource of type [com.example.MyBean] has been registered. It is required for one of the handlers being executed.] with root cause

org.axonframework.test.FixtureExecutionException: No resource of type [com.example.MyBean] has been registered. It is required for one of the handlers being executed.
	at org.axonframework.test.FixtureResourceParameterResolverFactory$FailingParameterResolver.resolveParameterValue(FixtureResourceParameterResolverFactory.java:58)
	at org.axonframework.messaging.annotation.AnnotatedMessageHandlingMember.resolveParameterValues(AnnotatedMessageHandlingMember.java:177)
	at org.axonframework.messaging.annotation.AnnotatedMessageHandlingMember.handle(AnnotatedMessageHandlingMember.java:153)
	at io.holixon.axon.projection.adhoc.EventApplier.applyEvent(EventApplier.kt:33)

The underlying issues lies by directly instantiating ClasspathParameterResolverFactory here:

axon-adhoc-projection/extension/core/src/main/kotlin/io/holixon/axon/projection/adhoc/ModelInspector.kt

Line 18 in 1773122

val parameterResolverFactory = ClasspathParameterResolverFactory.forClass(inspectedType)

where as for a usage with Spring we would need a MultiParameterResolverFactory which is set up with additional Spring specific resolvers (see how Axon does it here)

Solution: When running with Spring it should reuse the existing instance of ParameterResolverFactory in the application context.

Wanted Behaviour

The Spring bean (which is declared and registered in the application context) is resolved and the message handler method called.

Possible Workarounds

Use workaround such as a application context provider to statically gain access the Spring application context and thus retrieving the required beans from the handler method.