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原理：反射

场景：AOP 

一、类有接口-JDK代理

interface PeoPle{void work();String eat(String food);
}class Man implements PeoPle{@Overridepublic void work() {System.out.println("I am work");}@Overridepublic String eat(String food) {System.out.println("我喜欢吃"+ food);return food;}
}class ManProxy implements InvocationHandler{private static Object object;public static Object getProxyInstance(Object obj) {object = obj;/*** newProxyInstance()：此方法用于返回一个代理类的对象，* 第一个参数为被代理类的类加载器，* 第二个参数为被代理类所实现的接口,* 第三个参数是代理类 代理 被代理类 要执行的方法所在的类的实例(当我们通过代理类的对象，调用方法a时，会自动调用下面的invoke()方法)*/return Proxy.newProxyInstance(object.getClass().getClassLoader(),object.getClass().getInterfaces(),new ManProxy());}@Overridepublic Object invoke(Object proxy, Method method, Object[] args) throws Exception {//JDK动态代理的增强方法handle();System.out.println("拦截方法"+method);System.out.println("方法参数：" + Arrays.toString(args));//我们可以在此方法 Object obj = method.invoke(targetObject,args);前后新增方法可以增强原方法return method.invoke(object,args);}private void handle(){//处理一些业务逻辑System.out.println("JDKProxy处理业务逻辑");}
}public class JDKProxy{public static void main(String[] args) throws Exception{Man man = new Man();PeoPle proxyInstance = (PeoPle) ManProxy.getProxyInstance(man);String foods = proxyInstance.eat("foods");}
}

二、类无接口-CGLIB代理

class Animal{public String eat(String food){return food;}public void call(String str){System.out.println("Animal is "+ str + " call");}
}public class CGLBProxy implements MethodInterceptor {// CGlib需要代理的目标对象private Object targetObject;public Object createProxyObject(Class obj) throws Exception{this.targetObject = obj.newInstance();//1.工具类Enhancer enhancer = new Enhancer();//2.设置父类enhancer.setSuperclass(targetObject.getClass());//3.设置回调函数enhancer.setCallback(this);System.out.println("this -> "+this);//4.创建子类(代理对象)Object proxyObj = enhancer.create();return proxyObj;}@Overridepublic Object intercept(Object o, Method method, Object[] args, MethodProxy methodProxy) throws Throwable {System.out.println("这是增强方法前......");System.out.println("获取拦截方法：" + method.getName());System.out.println("获取方法参数：" + Arrays.toString(args));System.out.println("MethodProxy：" + methodProxy);Object obj = method.invoke(targetObject, args);System.out.println("这是增强方法后......");//模拟一下新增部分业务逻辑handle();return obj;}private void handle(){//处理一些业务逻辑System.out.println("CGLibProxy处理业务逻辑");}public static void main(String[] args) throws Exception{Animal proxyObject = (Animal) new CGLBProxy().createProxyObject(Animal.class);proxyObject.call("miao miao");String food = proxyObject.eat("food");System.out.println(food);}
}