Is Java Reflection is Deprecated in version 9 and later?
How will the Spring works in Java 9 and later versions?
Does Spring uses bytecode internally or how does it executes the method in all cases?
Does Spring uses CGLIB and low level ASM in all cases?
Deprecated doesn't mean you can't use a feature.The big change with Java 9 is that you have the option (but not requirement) to use modules. And modules is what enforces boundaries and causes problems with some types of reflection.
As far as I know, Spring 5 "solves" this by not supporting modules.