Reflection + annotations implement AOP

/** * @author xyf * @date 2021/7/7 11:09 */ @Retention(RetentionPolicy.RUNTIME) @Target(ElementType.TYPE) public @interface Aspect {/* Public Class type(); }Copy the code

public interface IAspect {
void before();
void after();
}
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public interface IOrder {

void pay(String number, String number2) throws InterruptedException;

void show();
}
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public class ObjectFactory {

public static <T> T newInstance(Class<T> clazz) throws NoSuchMethodException, IllegalAccessException, InvocationTargetException, InstantiationException {

	Annotation[] annotations = clazz.getAnnotations();
	LinkedList<IAspect> aspects = new LinkedList<IAspect>();
	// 获取类上 所有的aspect注解 的 附关注点的类
	for (Annotation annotation : annotations) {
		if (annotation instanceof Aspect) {
			Class type = ((Aspect) annotation).type();
			IAspect iAspect = (IAspect) type.getConstructor().newInstance();
			aspects.push(iAspect);
		}
	}

	// 构造 T
	T inst = clazz.getConstructor().newInstance();
	//创建代理
	T t = (T) Proxy.newProxyInstance(
			clazz.getClassLoader(),
			clazz.getInterfaces(),
			new InvocationHandler() {
				@Override
				public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
					aspects.forEach(IAspect::before);
                                         
					Object result = method.invoke(inst, args);
					aspects.forEach(IAspect::after);
					return result;
				}
			}
	);
	return  t;
}

@Test
public void test() throws InvocationTargetException, NoSuchMethodException, InstantiationException, IllegalAccessException, InterruptedException {
	IOrder order =  ObjectFactory.newInstance(Order.class);
	order.pay("1111", "22222");
	order.show();
}
}
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@Aspect(type = TimeUsageAspect.class) public class Order implements IOrder { int state = 0; @Override public void pay(String number,String number2) throws InterruptedException { Thread.sleep(50); // This. State = 1; System.out.println(" input parameter 1"+number); System.out.println(" input parameter 1"+number2); } @Override public void show() { System.out.println("order status:" + this.state); }}Copy the code

public class TimeUsageAspect implements IAspect { long start; @Override public void before() { start = System.currentTimeMillis(); } @Override public void after() { long usage = System.currentTimeMillis() - start; System.out.format("time usage : %dms\n", usage); }}Copy the code