Java Spring - Spring AOP advice & AspectJ

• 建立annotated aspects
• AspectJ5的特性
• 簡便的通過少量的annotation把任意class轉變為aspect
• 定義aspect
• 一場表演，觀眾很重要，但對演出功能本身而言，觀眾並不是必要。因此，在Performance上，觀眾是aspect，並將其應用到Performance

@Aspect
public class Audience {
    @Before("execution(** concert.Performance.perform(..))") //perform()之前
    public void silenceCellPhones() {
        System.out.println("Silencing cell phones");
    }

    @Before("execution(** concert.Performance.perform(..))") //perform()之前
    public void takeSeats() {
        System.out.println("Taking seats");
    }

    @AfterReturning("execution(** concert.Performance.perform(..))") //perform()成功執行後
    public void applause() {
        System.out.println("CLAP CLAP CLAP!!!");
    }

    @AfterThrowing("execution(** concert.Performance.perform(..))") //表演失敗之後

    public void demandRefund() {
        System.out.println("Demanding a refund");
    }
}