package com.young.spring.aop;

import org.aspectj.lang.JoinPoint;
import org.aspectj.lang.ProceedingJoinPoint;
import org.aspectj.lang.annotation.*;
import org.springframework.core.annotation.Order;
import org.springframework.stereotype.Component;

import java.util.Arrays;

/**
 * 可以使用 @Order注解指定切面的优先级,值越小优先级越高
 */
@Order(2)
@Aspect
@Component
public class LoggingAspect {

    /**
     * 定义一个方法,用于声明切入点表达式,一般地,该方法中再不需要添入其他的代码
     * 使用 @Pointcut来声明切入点表达式
     * 后面的其他通知直接使用方法名来引用当前的切入点表达式
     */
    @Pointcut("execution(public int com.young.spring.aop.ArithmeticCalculator.*(..))")
    public void declareJointPointExpression() {
    }

    /**
     * 在com.young.spring.aop.ArithmeticCalculator接口的每一个实现类的每一个方法开始之前执行一段代码
     */
    @Before("declareJointPointExpression()")
    public void beforeMethod(JoinPoint joinPoint) {
        String methodName = joinPoint.getSignature().getName();
        Object[] args = joinPoint.getArgs();
        System.out.println("The method " + methodName + " begins with " + Arrays.asList(args));
    }

    /**
     * 在方法执行之后执行的代码,无论该方法是否出现异常
     */
    @After("declareJointPointExpression()")
    public void afterMethod(JoinPoint joinPoint) {
        String methodName = joinPoint.getSignature().getName();
        System.out.println("The method " + methodName + " ends");
    }

    /**
     * 在方法正常结束后执行的代码
     * 返回通知是可以访问到方法的返回值的!
     */
    @AfterReturning(value = "declareJointPointExpression()", 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的代码
     * 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代码
     */
    @AfterThrowing(value = "declareJointPointExpression()", throwing = "ex")
    public void afterThrowing(JoinPoint joinPoint, Exception ex) {
        String methodName = joinPoint.getSignature().getName();
        System.out.println("The method " + methodName + " occurs 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 类型的参数可以决定是否执行目标方法
     * 环绕通知必须有返回值,返回值即为目标方法的返回值
     */
    @Around(value = "execution(public int com.young.spring.aop.ArithmeticCalculator.*(..))")
    public Object aroundMethod(ProceedingJoinPoint pjd) {

        Object proceed = 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()));
            proceed = pjd.proceed();
            //返回通知
            System.out.println("The method ends with " + proceed);
        } catch (Throwable throwable) {
            //异常通知
            System.out.println("The method occurs exception " + throwable);
        }
        //后置通知
        System.out.println("The method " + methodName + " ends");
        return proceed;
    }

}

package com.young.spring.aop;

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;

import java.util.Arrays;

@Order(1)
@Aspect
@Component
public class ValidationAspect {

    @Before("LoggingAspect.declareJointPointExpression()")
    public void validationArgs(JoinPoint joinPoint) {
        System.out.println("-->validate: " + Arrays.asList(joinPoint.getArgs()));
    }

}

package com.young.spring.aop;

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");
        int result = arithmeticCalculator.add(1, 2);
        System.out.println("result: " + result);

        result = arithmeticCalculator.div(1000, 10);
        System.out.println("result: " + result);
    }

}