Axon simple event bus and kafka serializer

i used kafka as event bus. but now i’m removing it.
in one application, i only use simple event bus and command handler, event handler

but it suddenly occured the error.

2022-06-21 07:05:51.226  INFO 1 --- [untProcessor]-0] o.a.e.TrackingEventProcessor             : An error occurred while attempting to claim a token for segment: 0. Will retry later...
java.lang.ClassCastException: org.axonframework.serialization.UnknownSerializedType cannot be cast to org.axonframework.eventhandling.TrackingToken
at org.axonframework.eventhandling.tokenstore.AbstractTokenEntry.getToken( ~[axon-messaging-4.5.8.jar:4.5.8]
at org.axonframework.extensions.mongo.eventsourcing.tokenstore.MongoTokenStore.fetchToken( ~[axon-mongo-4.5.jar:4.5]
at org.axonframework.eventhandling.TrackingEventProcessor$WorkerLauncher.lambda$run$2( ~[axon-messaging-4.5.8.jar:4.5.8]

what’s wrong with it? if i remove mongo and re-install, it work well.
but first using kafka as event bus, and then change it to simple event bus, it didn’t work well.

i don’t know why it happen

please someone tell me the reason

how it work?

Not sure but could it be it tries to load a token used with Kafka, so from the Kafka extension project? If you change the source you are reading from, and have stored tokens, you most likely want to clean up the stored tokens at the same time.
It seems like that might be what’s happening here.

@Gerard thank you to let me know!