Implementation steps of dynamic proxy

Write it at the front ： Implement an agent , Whether static or dynamic , Generally, you need to create three classes and an interface ： The inherited interfaces （ Provides all the methods needed to implement the class ）, Delegation class （ Is the implementation class , It can be more than one ）, proxy class （ All tasks of the implementation class are entrusted to the proxy class ）, client （ Start the program , discharge main Where the function is ）

Implementation steps of dynamic agent ：

1. new An implementation class object ;
2. Get the proxy object that implements the class object ：
   2.1 call Proxy.newProxyInstance To get a dynamic proxy object , It takes three parameters , The meanings of the three parameters are respectively ：
   ① One ClassLoader object , Defined by which ClassLoader Object to load the generated proxy object
   ② One Interface An array of objects , What is the set of interfaces that I'm going to provide to the object that I need to proxy , If I provide a set of interfaces to it , The proxy object then claims to implement the interface ( polymorphic ), So I can call methods in this set of interfaces
   ③ One InvocationHandler Implementation class object of , Represents when my dynamic proxy object is calling a method , Which one does it relate to
   InvocationHandler On the implementation class object of
   3. Get the class object of the proxy object （ Here we can print the class name of the class object of the proxy class ）
   4. Get all the methods of the proxy class （ Through violent reflection getDeclaredMethods（） get ）（ Traverse all the obtained methods , Output all method names ）
   5. The method of implementing class is called by proxy object （ And the assignment ）, Trigger our key steps ：InvocationHandler In the implementation class of the interface invoked（） Method , To execute the method that implements the class （sout Output the result ）（ This step is called non intrusive coding rules ）
   5.1 call InvocationHandler The interface steps are as follows ：
   After triggering the method that implements the class , The first thing you need to do is InvocationHandler Three parameters are passed in the interface , Namely
   ① proxy:　 - Refers to the real object that we are representing
   ② method:　- It refers to a method that we want to call on a real object Method object （）
   ③ args:　　- Refers to the parameters that are accepted when a method is called on a real object
   After that, the interface specific invoked（） Method , Pass in two parameters , They are the real implementation class object and the parameters passed in args, Finally, return the method .