// 抽象主题角色

public interface Sleep {

    void sleep();

}

// 真实主题角色

public class SleepImpl implements Sleep {

    @Override

    public void sleep() {

        System.out.println("熟睡中");

    }

}

//动态处理器

public class DynamicProxyHandler implements InvocationHandler {

    private Object obj ;

    public  DynamicProxyHandler(final Object obj) {

        this.obj = obj;

    }

    @Override

    public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {

        System.out.println("睡觉前要刷牙");

        Object result = method.invoke(obj, args);

        System.out.println("睡醒后要吃早饭");

        return null;

    }

}

//测试代码

public class ProxyTest {

    public static void main(String[] args) {

        Sleep sleep = new SleepImpl();

        DynamicProxyHandler dph = new DynamicProxyHandler(sleep);

        Sleep sleepProxy = (Sleep) Proxy.newProxyInstance(sleep.getClass().getClassLoader(),

                sleep.getClass().getInterfaces(), dph);

        sleepProxy.sleep();

    }

}

结果：睡觉前要刷牙

      熟睡中

      睡醒后要吃早饭

@CallerSensitive

    public static Object newProxyInstance(ClassLoader loader,

                                          Class<?>[] interfaces,

                                          InvocationHandler h)

        throws IllegalArgumentException

    {

        Objects.requireNonNull(h);

        final Class<?>[] intfs = interfaces.clone();

        final SecurityManager sm = System.getSecurityManager();

        if (sm != null) {

            checkProxyAccess(Reflection.getCallerClass(), loader, intfs);

        }

        /*

         * Look up or generate the designated proxy class.

         */

        Class<?> cl = getProxyClass0(loader, intfs);

        /*

         * Invoke its constructor with the designated invocation handler.

         */

        try {

            if (sm != null) {

                checkNewProxyPermission(Reflection.getCallerClass(), cl);

            }

            final Constructor<?> cons = cl.getConstructor(constructorParams);

            final InvocationHandler ih = h;

            if (!Modifier.isPublic(cl.getModifiers())) {

                AccessController.doPrivileged(new PrivilegedAction<Void>() {

                    public Void run() {

                        cons.setAccessible(true);

                        return null;

                    }

                });

            }

            return cons.newInstance(new Object[]{h});

        } catch (IllegalAccessException|InstantiationException e) {

            throw new InternalError(e.toString(), e);

        } catch (InvocationTargetException e) {

            Throwable t = e.getCause();

            if (t instanceof RuntimeException) {

                throw (RuntimeException) t;

            } else {

                throw new InternalError(t.toString(), t);

            }

        } catch (NoSuchMethodException e) {

            throw new InternalError(e.toString(), e);

        }

    }