Currently web handler method params do not explicitly have to be annotated with @ProjectedPayload in order to be proxied for projection.

This implicit support has proven to cause quite some problems. One such example can be found in #3258 where a parameter defintion of @ModelAttribute MultipartFile file attempts to be proxied but fails for a reason unclear to the user.

The ultimate goal of this issue is to stop supporting proxying of web handler method params that are not explicitly annotated w/ @ProjectedPayload (either at the type or method param level).

In order to embrace the principle of upgrade empathy the plan is as follows.

• 4.0 - Log warning when param is not annotated with @ProjectedPayload #3300
• 4.1 - Stop supporting params that are not annotated with @ProjectedPayload #3301
• 4.2 - Remove the warn logging about params not annotated with @ProjectedPayload #3302