切面的优先级

1.可以使用@Order注解指定切面的优先级，值越小优先级越高

示例：

VlidationAspect.java：

package com.hk.spring.aop.notice;

import java.util.Arrays;

import org.aopalliance.intercept.Joinpoint;
import org.aspectj.lang.JoinPoint;
import org.aspectj.lang.annotation.Aspect;
import org.aspectj.lang.annotation.Before;
import org.springframework.core.annotation.Order;
import org.springframework.stereotype.Component;

@Order(1)
@Aspect
@Component
public class VlidationAspect {
    
    @Before("execution(public int com.hk.spring.aop.notice.ArithmeticCalculator.*(..))")
    public void validateArgs(JoinPoint joinPoint){
        System.out.println("-->validate:" + Arrays.asList(joinPoint.getArgs()));
    }

}

package com.hk.spring.aop.notice;

import java.util.Arrays;

import org.aopalliance.intercept.Joinpoint;
import org.aspectj.lang.JoinPoint;
import org.aspectj.lang.ProceedingJoinPoint;
import org.aspectj.lang.annotation.AfterReturning;
import org.aspectj.lang.annotation.AfterThrowing;
import org.aspectj.lang.annotation.Around;
import org.aspectj.lang.annotation.Aspect;
import org.aspectj.lang.annotation.Before;
import org.springframework.core.annotation.Order;
import org.springframework.stereotype.Component;

@Order(2)
@Aspect
@Component
public class LoggingAspect {
    /*
     * 在方法正常执行后执行的通知叫返回通知
     * 返回通知是可以访问到方法的返回值的
     */
//    @AfterReturning(value="execution(public int com.hk.spring.aop.notice.ArithmeticCalculator.*(..))",
//                    returning="result")
//    public void afterReturning(JoinPoint joinPoint,Object result){
//        String methodName = joinPoint.getSignature().getName();
//        System.out.println("The method " + methodName + " ends with " + result);
//    }
    
    /*
     * 在目标方法出现异常时，会执行代码。
     * 可以访问到异常对象；且可以指定在出现特定异常时在执行通知
     */
//    @AfterThrowing(value="execution(public int com.hk.spring.aop.notice.ArithmeticCalculator.*(..))",
//                   throwing="ex")
//    public void afterThrowing(JoinPoint joinPoint,Exception ex){
//        String methodName = joinPoint.getSignature().getName();
//        System.out.println("The method " + methodName + " coours exception : " + ex);
//    }
    
    /*
     * 环绕通知需要携带ProceedingJoinPoint 类型的参数
     * 环绕通知类似于动态代理的全过程：ProceedingJoinPoint这个类型的参数可以决定是否执行目标方法
     * 且环绕通知必须有返回值，返回值即为目标方法的返回值
     */
    @Around("execution(public int com.hk.spring.aop.notice.ArithmeticCalculator.*(..))")
    public Object aroundMethod(ProceedingJoinPoint pjd){
        
        Object result = null;
        String methodName = pjd.getSignature().getName();
        
        //执行目标方法
        try {
            //前置通知
            System.out.println("The method " + methodName + "begins with " + Arrays.asList(pjd.getArgs()));
            result = pjd.proceed();
            //后置通知
            System.out.println("The method " + methodName + "ends with " + result);
        } catch (Throwable e) {
            //异常通知
            System.out.println("The method occurs exception:" + e);
        }
        //后置通知
        System.out.println("The method " + methodName + " ends");
        return result;
    }
}

Main.java：

package com.hk.spring.aop.notice;

import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

public class Main {

    public static void main(String[] args) {
        ApplicationContext ctx = new ClassPathXmlApplicationContext("applicationContext.xml");
        ArithmeticCalculator arithmeticCalculator = (ArithmeticCalculator) ctx.getBean("ArithmeticCalculator");
        
        System.out.println(arithmeticCalculator.getClass().getName());
        
        int result = arithmeticCalculator.add(1, 2);
        System.out.println("result: " + result);
        
        result = arithmeticCalculator.div(1000, 10);
        System.out.println("result " + result);

    }

}

运行结果：

由结果可以看出，验证切面优先于日志切面。