19Spring返回通知&异常通知&环绕通知

package com.cn.spring.aop.impl;
//加减乘除的接口类
public interface ArithmeticCalculator {
int add(int i, int j);
int sub(int i, int j);
int mul(int i, int j);
int div(int i, int j);
}

package com.cn.spring.aop.impl;

import org.springframework.stereotype.Component;

//实现类
@Component
public class ArithmeticCalculatorImpl implements ArithmeticCalculator {
@Override
public int add(int i, int j) {
int result = i + j;
return result;
}

@Override
public int sub(int i, int j) {
int result = i - j;
return result;
}

@Override
public int mul(int i, int j) {
int result = i * j;
return result;
}

@Override
public int div(int i, int j) {
int result = i / j;
return result;
}
}

package com.cn.spring.aop.impl;

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

import java.util.Arrays;
import java.util.List;

//把这个类声明为一个切面：首先需要把该类放入到IOC容器中，在声明为一个切面
@Aspect
@Component
public class LoggingAspect {

//声明该方法是一个前置通知：在目标方法开始之前执行
@Before("execution(public int ArithmeticCalculator.*(int, int))")
public void beforeMethod(JoinPoint joinPoint) {
String methodName = joinPoint.getSignature().getName();
List<Object> args = Arrays.asList(joinPoint.getArgs());

System.out.println("The method " +  methodName + " begins with " + args);
}

//后置通知：在目标方法执行后（无论是否发生异常），执行的通知
//在后置通知中还不能访问目标方法执行的结果
@After("execution(public int ArithmeticCalculator.*(int, int))")
public void afterMethod(JoinPoint joinPoint) {
String methodName = joinPoint.getSignature().getName();
List<Object> args = Arrays.asList(joinPoint.getArgs());

System.out.println("The method " +  methodName + " ends with " + args);
}

/**
* 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
* @param joinPoint
*/
@AfterReturning(value = "execution(public int ArithmeticCalculator.*(int, int))",
returning = "result")
public void afterReturning(JoinPoint joinPoint, Object result) {
String methodName = joinPoint.getSignature().getName();
List<Object> args = Arrays.asList(joinPoint.getArgs());

System.out.println("The method  ends witd " + 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再执行通知代码
@AfterThrowing(value = "execution(public int ArithmeticCalculator.*(int, int))",
throwing = "ex")
public void afterReturning(JoinPoint joinPoint, Exception ex) {
String methodName = joinPoint.getSignature().getName();

System.out.println("The method " +  methodName + " occures exception with: " + 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
* 且环绕通知必须有返回值，返回值为目标方法的返回值
* @param proceedingJoinPoint
*/
@Around("execution(public int ArithmeticCalculator.*(int, int))")
public Object aroundMethod(ProceedingJoinPoint proceedingJoinPoint) {
Object result = null;
String methodName = proceedingJoinPoint.getSignature().getName();
//执行目标方法
try {
//前置通知
System.out.println("The method " +  methodName + " begins with " + Arrays.asList(proceedingJoinPoint.getArgs()));
result = proceedingJoinPoint.proceed();
//返回通知
System.out.println("The method ends with " + result);
} catch (Throwable throwable) {
//异常通知
System.out.println("The method " +  methodName + " occures exception with: " + throwable);
throw new RuntimeException(throwable);
}
//后置通知
System.out.println("The method " +  methodName + " ends");
return result;
}
}

package com.cn.spring.aop.impl;

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

public class Main {
public static void main(String[] args) {
//1.创建Spring的IOC容器
ApplicationContext ctx = new ClassPathXmlApplicationContext("17-1.xml");

//2.从IOC容器中huo获取bean的实例
ArithmeticCalculator arithmeticCalculator = ctx.getBean(ArithmeticCalculator.class);

//3.使用bean
int result = arithmeticCalculator.add(3, 6);

System.out.println("result:" + result);
//result = arithmeticCalculator.div(3, 0);
// System.out.println("result:" + result);
}
}

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:context="http://www.springframework.org/schema/context"
xmlns:aop="http://www.springframework.org/schema/aop"
xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context.xsd http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop.xsd"> <context:component-scan base-package="com.cn.spring.aop.impl">
</context:component-scan>

<!--使AspjectJ注解起作用：自动为匹配的类生成代理对象-->
<aop:aspectj-autoproxy></aop:aspectj-autoproxy>
</beans>