AF5 Nullable injectable entities?

Axon Framework
1

Let’s say I have a command handler that injects a state object:

@CommandHandler
fun handle(
    command: Command,
    @InjectEntity(idProperty = "property") state: State,
    eventAppender: EventAppender,
) {
  ...
}

This requires me to have the idProperty set in my command. Otherwise, I will get a framework error.

I do not think this is ideal for at least 2 reasons:

  1. My command may be malformed, but I want to be able to handle the error inside my command handling method to output a functional exception.
  2. It may be (especially with more than 1 entity to be injected) that a an absent entity is not an invalid state. An event may have nullable relations in a DCB context, it requires only 1 non-nullable tag (if even that).

I encounter both of these reasons in our use cases.

So what I would like to do is the following:

data class Command(val property: String?, ...)

@CommandHandler
fun handle(
    command: Command,
    @InjectEntity(idProperty = "property") state: State?, // nullable
    eventAppender: EventAppender,
) {
  if(state==null) { 
    // handle nullability
  }
}

Where the state resolves to `null` (or empty, if you want to go the optional route, which may make more sense in Java) in case the property in the command is null.

Is there in the current implementation a workaround for this? I have tried to build something, but I’m running into issues every time.

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