spring aop环绕通知

​​【Spring实战】—— 9 AOP环绕通知​​

假如有这么一个场景，需要统计某个方法执行的时间，如何做呢？

　　典型的会想到在方法执行前记录时间，方法执行后再次记录，得出运行的时间。

如果采用Spring的AOP，仅仅使用前置和后置方法是无法做到的，因为他们无法共享变量。这样通过环绕通知，就可以快捷的实现。

　　首先在切面通知类中声明环绕通知类：

public void watchPerformance(ProceedingJoinPoint joinpoint){
        try{
            System.out.println("begin!");
            long start = System.currentTimeMillis();

            joinpoint.proceed();

            long end = System.currentTimeMillis();
            System.out.println("end!        performance took "+(end-start)+" milliseconds");
        }catch(Throwable e){
            System.out.println("eee!We want our money back!");
        }
    }      

　　在bean.xml配置文件中配置aop:around，锁定方法：

<aop:around pointcut-ref="performance" method="watchPerformance"/>      

　　这样执行的结果如下：

The audience is taking their seats.
The audience is turning off their cellphones
begin!
Instrumentalist age:25
Playing Jingle Bells:TOOT TOOT TOOT
CLAP CLAP CLAP
end!        performance took 95 milliseconds      

　　因此可以看出AOP执行的过程如下：

before()
　　around()
　　执行方法()
　　after/throw()
　　around()      

public void watchPerformance(ProceedingJoinPoint joinpoint){
        try{
            System.out.println("begin!");
            long start = System.currentTimeMillis();

            joinpoint.proceed();

            long end = System.currentTimeMillis();
            System.out.println("end!        performance took "+(end-start)+" milliseconds");
        }catch(Throwable e){
            System.out.println("eee!We want our money back!");
        }
    }      

<aop:around pointcut-ref="performance" method="watchPerformance"/>      

The audience is taking their seats.
The audience is turning off their cellphones
begin!
Instrumentalist age:25
Playing Jingle Bells:TOOT TOOT TOOT
CLAP CLAP CLAP
end!        performance took 95 milliseconds      

before()
　　around()
　　执行方法()
　　after/throw()
　　around()