The annotation is self-defined by implementing the parameter parser handlermethodargumentresolver interface

HandlerMethodArgumentResolver Similar to interceptors , Is a parameter parser , We can implement... By writing a class HandlerMethodArgumentResolver Interface to implement Controller Modification of method parameters in layer

Custom parser needs to be implemented HandlerMethodArgumentResolver Interface ,HandlerMethodArgumentResolver The interface contains two interface functions :

When supportsParameter return True when , Will call resolveArgument.

example ：
Declare custom annotations （ Used to get the user's userid）

Write a LoginUserHandlerMethodArgumentResolver Class implementation HandlerMethodArgumentResolver Interface

stay resolveArgument Will get token, And then according to token obtain userid And back to