Automatic propagation of MetaData from Command to Event - is it possible?

Axon Framework
1

I want to use MetaData to store the origin of an event. Use Case, we have 2+ apps publishing the same commands/events and I need to filter that each app only handles its own (triggered by it) events.

I managed to register a commondDispatch Interceptor that adds the spring.application.name to MetaData. But I only can access the value if I manually do

@CommandHandler
fun handle(cmd: MyCommand, meta: MetaData) {
  AggregateLifecycle.apply(myEvent, meta)
}

if I do not manually transport the metaData from handle-fun to apply-call, it is lost.

I was under the impression, that meta data is propagated automatically …

(note: although my use case will be spring based, I currently am working with an AggregateTestFixture and the registerCommandDispatcher feature).

Any hints how I can achieve what I need and how I can test this using fixtures?

Thanks

2

Hi Jan,

have you checked the Correlation Data Provider option from here? It seems that utilizing message correlation could be beneficial in your situation.

Hope this helps.

Kind regards,
Stefan

1 Like
3

Thanks a lot, Stefan. Yes, this is exactly what I was looking for.

I also enhanced our axon-jgiven test lib so CorrelationDataProviders can be registered in fixture based tests:

    // adds "foo" metaData
    private fun addFooMetaToEveryCommand(value: String) = MessageDispatchInterceptor<CommandMessage<*>> {
      BiFunction { _, cmd -> cmd.andMetaData(mapOf("foo" to value)) }
    }

    @ProvidedScenarioState
    val fixture = AxonJGiven.aggregateTestFixtureBuilder<DummyAggregate>()
      .registerCommandDispatchInterceptor(addFooMetaToEveryCommand("bar"))
      // correlates "foo"
      .registerCorrelationDataProvider(SimpleCorrelationDataProvider("foo"))
      .build()

    @Test
    fun `metaData foo=bar is propagated to event`() {
      GIVEN.noPriorActivity()

      WHEN.command(CreateDummyAggregate("1"))

      // asserts that "foo"="bar" is part of the DomainEventMessage
      THEN
        .expectEventWithMetaData(DummyAggregateCreated("1"), "foo" to "bar")
    }
2 Likes