`MultipartFile` instance empty when consumed via an `@ApplicationModuleListener` about spring-modulith HOT 2 CLOSED

I guess the problem here is that a MultipartFile is directly backed by the input stream of the incoming request, which in turn is tied to the thread receiving it. Any chance you copy the content into a separate data structure first?

Just to make sure: it's not obvious from the code you showed what exactly happens to the MultipartImage within ProductFile. You just state “it is empty” without clarifying what “it” refers to.

Finally, the code in the listener looks a bit suspicious. Application module listeners are intended to react to completed units of work in a foreign model. They are not intended to re-implement a request/response via events. In other words, we recommend the original business transaction to result in a valid state and the events solely transferring pointers to that state.

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I guess the problem here is that a MultipartFile is directly backed by the input stream of the incoming request, which in turn is tied to the thread receiving it. Is there any chance you could copy the content into a separate data structure first?

This assumption is true. When passing a MultipartFile in the module listeners, it seems like the binary content of the MultipartFile is wiped out. That’s why I say it is empty upon reception.

Finally, the code in the listener looks a bit suspicious. Application module listeners are intended to react to completed units of work in a foreign model. They are not intended to re-implement a request/response via events. In other words, we recommend that the original business transaction results in a valid state and that the events solely transfer pointers to that state.

You’re also right here. After posting my issue, I reread DDD by Eric Evans and realized that I missed that point, each events should be propagate when the unit of work is completed. Thanks for your feedback.

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