关于spring aop Advisor排序问题

示例代码：

import org.aspectj.lang.ProceedingJoinPoint;

import org.aspectj.lang.annotation.Around;

import org.aspectj.lang.annotation.Aspect;

import org.aspectj.lang.annotation.Pointcut;

import org.slf4j.Logger;

import org.slf4j.LoggerFactory;

import org.springframework.core.Ordered;

import org.springframework.core.annotation.Order;

/**

 * @author yaojiafeng

 * @create 2017-09-11 下午3:32

 */

@Aspect

@Order(1)

public class LogAspect implements Ordered {

    Logger logger = LoggerFactory.getLogger(LogAspect.class);

    @Pointcut("@annotation(com.yaojiafeng.test.aop.LogMDC)")

    public void log() {

    }

    @Around("log()")

    public Object log(ProceedingJoinPoint proceedingJoinPoint) throws Throwable {

        String interfaceName = proceedingJoinPoint.getTarget().getClass().getName();

        String methodName = proceedingJoinPoint.getSignature().getName();

        Object[] args = proceedingJoinPoint.getArgs();

        Object obj = null;

        try {

            obj = proceedingJoinPoint.proceed();

        } finally {

            logger.info(interfaceName + "-" + methodName + "-" + obj + "-" + args);

        }

        return obj;

    }

    @Override

    public int getOrder() {

        return 1;

    }

}

spring aop会在AnnotationAwareAspectJAutoProxyCreator处理bean查找到适配的Advisor的时候对所有Advisor进行排序并生成动态代理，AspectJAwareAdvisorAutoProxyCreator的sortAdvisors方法

@Override

	@SuppressWarnings("unchecked")

	protected List<Advisor> sortAdvisors(List<Advisor> advisors) {

		List<PartiallyComparableAdvisorHolder> partiallyComparableAdvisors =

				new ArrayList<PartiallyComparableAdvisorHolder>(advisors.size());

		for (Advisor element : advisors) {

			partiallyComparableAdvisors.add(

					new PartiallyComparableAdvisorHolder(element, DEFAULT_PRECEDENCE_COMPARATOR));

		}

		List<PartiallyComparableAdvisorHolder> sorted =

				PartialOrder.sort(partiallyComparableAdvisors);

		if (sorted != null) {

			List<Advisor> result = new ArrayList<Advisor>(advisors.size());

			for (PartiallyComparableAdvisorHolder pcAdvisor : sorted) {

				result.add(pcAdvisor.getAdvisor());

			}

			return result;

		}

		else {

			return super.sortAdvisors(advisors);

		}

	}

这里会根据每个Advisor的获取到的order值进行从小到大排序，order值获取规则如下：

1. 首先判断当前Advisor所在的切面类是否实现org.springframework.core.Ordered接口，是的话调用getOrder方法获取
2. 否则判断当前Advisor所在的切面类是否包含org.springframework.core.annotation.Order注解，是的话从注解获取
3. 没有取到值，默认为最低优先级，值为最大Int

从排序代码可知，有以下处理过程：

1. 打在Advice方法上的org.springframework.core.annotation.Order注解不予识别
2. 如果一个切面类存在多个Advisor，则会按Advice方法的声明顺序，声明在前的优先级高，先执行
3. 不同切面类但是order值是一样的，则按spring获取到切面bean的顺序做排序，先获取先执行