Java动态代理

public interface Subject {
    void printf();
}

public class RealSubject implements Subject {

    @Override
    public void printf() {
        System.out.println("this is a RealSubject‘s printf()");
    }
    
}

public class SubjectInvocationHandler implements InvocationHandler{

    //被代理的对象
    private Object proxy;
    public SubjectInvocationHandler(Object proxy) {
        this.proxy = proxy;
    }
    
    /**
     * proxy  调用方法的代理对象
     * method 调用的方法
     * args   调用方法的参数
     * return 调用方法的返回值
     */
    @Override
    public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
        System.out.println("SubjectInvocationHandler invoke prepare");
        Object result = method.invoke(this.proxy, args);
        System.out.println("SubjectInvocationHandler invoke post");
        return result;
    }

}

public class ProxyTest {

    public static void main(String[] args) {
        
        RealSubject realSubject = new RealSubject();
        Class<?> clz = realSubject.getClass();
        
        //获取代理类的class
        Class<?> proxyClz = Proxy.getProxyClass(clz.getClassLoader(), clz.getInterfaces());
        try {
            //获取带InvocationHandler参数的构造器
            Constructor<?> constructor = proxyClz.getConstructor(InvocationHandler.class);
            //利用构造器实例化代理对象
            Subject proxySubject = (Subject) constructor.newInstance(new SubjectInvocationHandler(realSubject));
            proxySubject.printf();
        } catch (Exception e) {
            e.printStackTrace();
        }
        
        //利用Proxy中的方法一步到位
        Subject proxySubject = (Subject) Proxy.newProxyInstance(clz.getClassLoader(), clz.getInterfaces(), new SubjectInvocationHandler(realSubject));
        proxySubject.printf();
        
    }

}