There are two small improvements which can be made in the new ResourceProvider API:
1. Add properties for marking a ResourceProvider as adaptable, refreshable and attributable.
It'll help to avoid the resource providers full-scan when invoking methods not related to a specific paths. Each registered servlet creates its own ResourceProvider and scanning them all every time someone calls ResourceResolver#adaptTo() might be slow.
2. Mark old ResourceProvider and ResourceProviderFactory as deprecated