Add support multipart request parts in @RequestBean

[altro3]

Fixed #11682

[altro3]

@graemerocher @dstepanov @yawkat Could you help with this feature?

This change is just the first step to be able to put the Part annotation at the field level in the RequestBean class. But how to add correct processing is not yet clear. Multipart request processing is implemented differently... It is hard for me to figure out where and what needs to be fixed to add this feature

[yawkat]

unfortunately as you say multipart is handled specially depending on server implementation, and is pretty complicated. this feature will probably have to wait for a unified multipart api

[altro3]

Any plans to do it? Ithink this is important to people, who want to migrate from spring to micronaut. Currently I foun only this feature thats not supported by micronaut, but supported by spring boot

[dstepanov]

@altro3 The parts are loaded async. Check NettyPartUploadAnnotationBinder and see that it returns PendingRequestBindingResult which will return Optional.empty if it's not yet resolved.
To implement this case you would need to convert the bind method of RequestBeanAnnotationBinder to return PendingRequestBindingResult with proper check for all the arguments isPending.

[yawkat]

@altro3 multipart improvements are WIP but it's a bit stuck in review on the netty side atm. netty-contrib/codec-multipart#25

maybe that situation will improve now that netty 4.2 is out.

[altro3]

oh, understand...

@yawkat Unfortunately the project looks dead... :-(

[yawkat]

It's not exactly dead, but there's just not very many people that are knowledgeable enough about netty and multipart to do such a big review. I've definitely not given up on it, it is a medium term priority for me.