Spring Framework & other Java equivalents have very fancy very complex intermediations like this, that let one apply all manner of modifiers to methods, at runtime.
It's not in the language per se. But Spring is able to either make new classes at runtime to suit or to have sufficiently capable proxies to do the instrumentation.
I've been pretty critical that metaprogramming & AOP have fallen away. They long have been semi troubled capabilities with not the best reputation, attracted a lot of animosity, but I think the potential value is just too high to pretend like we should stuff the genie back in the bottle.
