jdk动态代理

实现原理：利用字节码技术，生成新的class文件，来达到动态代理效果。

新的class文件是怎么组织的？由于代理目标是接口，则通过实现接口和继续代理类来完成。看看下面的例子更容易明白。

demo 接口

public interface PeoPleInterface {

    void say() throws Throwable;
}

实现类

public class GrilPeoPle implements PeoPleInterface {
    @Override
    public void say() {
        System.out.println("女人说");
    }
}

代理类

public class PeoPleInvacationHandler implements InvocationHandler {

    private Object obj;

    public PeoPleInvacationHandler(Object obj) {
        this.obj = obj;
    }

    @Override
    public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
        System.out.println("人类开始");
        Object invoke = method.invoke(obj, args);
        System.out.println("人类结束");
        return invoke;
    }
}

最终产生的类。这个类就是$Proxy0的实现原理。这个类是通过字节码生成的。

public class PeoPleProxy extends PeoPleInvacationHandler implements PeoPleInterface {

    public PeoPleProxy(Object obj) {
        super(obj);
    }

    @Override
    public void say() throws Throwable {
        // 调用目标方法
        super.invoke(this,PeoPleInterface.class.getMethod("say",null),null);
    }

    public static void main(String[] args) {
        PeoPleInterface grilPeoPle = new GrilPeoPle();
        PeoPleProxy proxy =new PeoPleProxy(grilPeoPle);
        try {
            proxy.say();
        } catch (Throwable throwable) {
            throwable.printStackTrace();
        }
    }
}