反射的应用之动态代理

代码源自 尚硅谷 java基础 day19_10反射的应用之动态代理

package com.william.java.reflection.proxy;

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

//动态代理接口的使用, 体会反射是动态语言的关键
interface Subject {
	void action();
}

// 被代理类
class RealSubject implements Subject {
	@Override
	public void action() {
		System.out.println("我是被代理类，记得要执行我哦^=^");
	}
}

//
class MyInvocationHandler implements InvocationHandler {
	Object obj;// 实现了接口的被代理类的对象的声明

	// 1.给被代理的对象实例化
	// 2.返回一个代理类的对象
	public Object blind(Object obj) {
		this.obj = obj;
		return Proxy.newProxyInstance(obj.getClass().getClassLoader(), obj.getClass().getInterfaces(), this);
	}

	// 当通过代理类的对象发起对被重写的方法的调用时，都会转换为对如下的 invoke 方法的调用
	@Override
	public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
		Object returnVal = method.invoke(obj, args);
		return returnVal;
	}

}

public class TestProxy {
	public static void main(String[] args) {
		// 1.被代理类的对象
		RealSubject realSubject = new RealSubject();
		// 2.创建一个实现了 InvocationHandler 接口的类的对象
		MyInvocationHandler handler = new MyInvocationHandler();
		// 3.调用 blind() 方法，动态的返回一个同样实现了 real 所在类实现的接口 Subject 的代理类的对象
		Object object = handler.blind(realSubject);
		Subject subject = (Subject) object;// 此时 sub 就是代理类的对象

		subject.action();// 转到对 InvacationHandler 接口的实现类的 invoke() 方法的调用

	}
}

通过以下代码加深 动态代理的理解

package com.william.java.reflection.proxy;

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

interface Person {
	void say();

	void eat();
}

interface Animal {
	void roar();

	void eat();
}

class TangWei implements Person {
	@Override
	public void say() {
		System.out.println("I'm TangWei, Hello");
	}

	@Override
	public void eat() {
		System.out.println("TangWei eat ice cream");
	}
}

class Angela implements Person {
	@Override
	public void say() {
		System.out.println("I'm Angela, Hello");
	}

	@Override
	public void eat() {
		System.out.println("Angela eat ice cream");
	}
}

class Cat implements Animal {
	@Override
	public void roar() {
		System.out.println("I'm a Cat, miao~");
	}

	@Override
	public void eat() {
		System.out.println("Cat eat mouse");
	}
}

class Dog implements Animal {
	@Override
	public void roar() {
		System.out.println("I'm a Dog, wang~");
	}

	@Override
	public void eat() {
		System.out.println("Dog eat bone");
	}
}

class MyInvHandler implements InvocationHandler {
	Object object;

	public Object blind(Object object) {
		this.object = object;
		return Proxy.newProxyInstance(object.getClass().getClassLoader(), object.getClass().getInterfaces(), this);
	}

	@Override
	public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {		
		return method.invoke(object, args);
	}

}

public class test {
	public static void main(String[] args) {
		TangWei tangWei = new TangWei();
		Angela angela = new Angela();
		Cat cat = new Cat();
		Dog dog = new Dog();

		MyInvHandler handler = new MyInvHandler();

		Person person = (Person) handler.blind(tangWei);
		person.say();
		person.eat();

		person = (Person) handler.blind(angela);
		person.say();
		person.eat();

		Animal animal = (Animal) handler.blind(cat);
		animal.eat();
		animal.roar();

		animal = (Animal) handler.blind(dog);
		animal.eat();
		animal.roar();

	}

}