Java反射的应用之动态代理深入理解

interface ClothFactory{
    void produceCloth();
}
//代理类
class ProxyClothFactory implements ClothFactory{
    private ClothFactory factory;//用被代理类对象进行实例化
    public ProxyClothFactory(ClothFactory factory){
        this.factory = factory;
    }
    @Override
    public void produceCloth() {
        System.out.println("代理工厂做一些准备工作");
        factory.produceCloth();
        System.out.println("代理工厂做一些后续的收尾工作");
    }
}
//被代理类
class NikeClothFactory implements ClothFactory{
 
    @Override
    public void produceCloth() {
        System.out.println("Nike工厂生产一批运动服");
    }
}
public class StaticProxyTest {
    public static void main(String[] args) {
        //创建被代理类的对象
        NikeClothFactory nike = new NikeClothFactory();
        //创建代理类的对象
        ProxyClothFactory proxyClothFactory = new ProxyClothFactory(nike);
        proxyClothFactory.produceCloth();
    }

interface Human{
    String getBelief();
    void eat(String food);
}
//被代理类
class SuperMan implements Human{
    @Override
    public String getBelief() {
        return "I believe I can fly!";
    }
 
    @Override
    public void eat(String food) {
        System.out.println("我喜欢吃" + food);
    }
}
class HumanUtil{
    public void method1(){
        System.out.println("===================通用方法一===============================");
    }
    public void method2(){
        System.out.println("===================通用方法二===============================");
    }
}

class ProxyFactory{
    //调用此方法，返回一个代理类的对象。解决问题一
    public static Object getProxyInstance(Object obj){//obj:被代理类的对象
        MyInvocationHandler handler = new MyInvocationHandler();
        handler.bind(obj);
        return Proxy.newProxyInstance(obj.getClass().getClassLoader(),obj.getClass().getInterfaces(),handler);
    }
}
class MyInvocationHandler implements InvocationHandler{
    private Object obj;//需要使用被代理类的对象进行赋值
    public void bind(Object obj){
        this.obj = obj;
    }
    //当我们通过代理类的对象，调用方法a时，就会自动的调用如下的方法：invoke()
    //将被代理类要执行的方法a的功能就声明在invoke()中
    @Override
    public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
 
        HumanUtil util = new HumanUtil();
        util.method1();
        //method:即为代理类对象调用的方法，此方法也就作为了被代理类对象要调用的方法
        //obj:被代理类的对象
        Object returnValue = method.invoke(obj,args);
 
        util.method2();
        //上述方法的返回值就作为当前类中的invoke()的返回值。
        return returnValue;
    }
}
public class ProxyTest{
    public static void main(String[] args) {
        SuperMan superMan = new SuperMan();
        Human proxyInstance = (Human) ProxyFactory.getProxyInstance(superMan);
        //当通过代理类对象调用方法时，会自动的调用被代理类中同名的方法
        String belief = proxyInstance.getBelief();
        System.out.println(belief);
        proxyInstance.eat("四川麻辣烫");
        System.out.println("************************************************");
        NikeClothFactory nikeClothFactory = new NikeClothFactory();
        ClothFactory proxyClothFactory = (ClothFactory) ProxyFactory.getProxyInstance(nikeClothFactory);
        proxyClothFactory.produceCloth();
    }