接口文件

package com.demo.service;

public interface Animal {

    public void eat();
}

实现类

package com.demo.service.impl;

import com.demo.service.Animal;

public class Dog implements Animal {

    public void eat() {
        System.out.println("dog eat");

    }

}

package com.demo;

import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;

public class MyInvocationHandler implements InvocationHandler {

    private Object target;
    
    public MyInvocationHandler() {
        
    }
    
    public MyInvocationHandler(Object target){
        this.target = target;
    }
    
    public Object invoke(Object arg0, Method arg1, Object[] arg2) throws Throwable {
        System.out.println("before eat");
        Object result = arg1.invoke(target, arg2);
        System.out.println("after eat");
        return result;
    }

}

package com.demo;

import java.lang.reflect.Proxy;

import com.demo.service.Animal;
import com.demo.service.impl.Dog;

public class TestProxy {

    public static void main(String[] args) {
        Animal dog = new Dog();
        MyInvocationHandler myInvocationHandler = new MyInvocationHandler(dog);
        Animal animal = (Animal)Proxy.newProxyInstance(dog.getClass().getClassLoader(),dog.getClass().getInterfaces(), myInvocationHandler);
        animal.eat();
    }
}

AOP就是通过动态代理的方式实现的。