Spring初学之annotation实现AOP前置通知后置通知返回通知异常通知。

Posted 2020-09-10

实现两个整数的加减乘除、在执行每个方法之前打印日志。

ArithmeticCalculator.java：

package spring.aop.impl;

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);
    
}

ArithmeticCalculatorImpl.java：

package spring.aop.impl;

import org.springframework.stereotype.Component;

@Component("arithmeticCalculator")
public class ArithmeticCalculatorImpl implements ArithmeticCalculator {

    public int add(int i, int j) {
        int result = i+j;
        return result;
    }

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

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

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

}

LoggingAspect.java：

package spring.aop.impl;

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

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


@Order(1)//如果有多个切面，可以使用@Order来指定切面的优先级，值越小优先级越高
@Aspect
@Component
public class LoggingAspect {
    
    /**
     * 定义一个方法，定义切入点表达式，一般地，这个方法中不添加其它代码
     * 怎么使用？
     * 1.如果在本类，如@Before("declareJoinPointExpression()"),直接用方法名来引用
     * 2.在另一个包的类或其他类，如@Before("包名.类名.declareJoinPointExpression()")
     */
    @Pointcut("execution(public int spring.aop.impl.ArithmeticCalculator.*(..))")
    public void declareJoinPointExpression(){}
    
    
    /**
     * 在spring.aop.impl.ArithmeticCalculator接口的每一个实现类的每一个开始之前执行一段代码
     */
    @Before("declareJoinPointExpression()")
    public void beforeMethod(JoinPoint joinPoint){
        String methodName=joinPoint.getSignature().getName();
        List<Object> args=Arrays.asList(joinPoint.getArgs());
        System.out.println("The method "+methodName+" begins "+args);
    }
    
    /**
     * 在方法之后执行（不论是否抛出异常）
     * @param joinPoint
     */
    @After("execution(public int spring.aop.impl.ArithmeticCalculator.*(..))")
    public void afterMethod(JoinPoint joinPoint){
        String methodName=joinPoint.getSignature().getName();
        List<Object> args=Arrays.asList(joinPoint.getArgs());
        System.out.println("The method "+methodName+" ends ");
    }
    
    /**
     * 在方法正常执行后的通知
     * 返回通知是可以访问到方法的返回值的
     * @param joinPoint
     */
    @AfterReturning(value="execution(public int spring.aop.impl.ArithmeticCalculator.*(..))",
            returning="result")
    public void afterReturnMethod(JoinPoint joinPoint,Object result){
        String methodName=joinPoint.getSignature().getName();
        System.out.println("The method "+methodName+" ends with afterReturning "+ result);
    }
    
    /**
     * 在目标方法出现异常时会执行的代码
     * 可以访问出现的异常信息，可以指定出现指定异常时执行
     * 方法参数Exception改为其它异常可以指定出现指定异常时执行
     * @param joinPoint
     * @param ex  
     */
    @AfterThrowing(value="execution(public int spring.aop.impl.ArithmeticCalculator.*(..))",
            throwing="ex")
    public  void afterThrowing(JoinPoint joinPoint,Exception ex){
        String methodName=joinPoint.getSignature().getName();
        System.out.println("The method "+methodName+" occurs exection: "+ ex);
    }
    
    /**
     * 环绕通知
     *    需要携带ProceedingJoinPoint类型的参数
     * 类似于动态代理的全过程：ProceedingJoinPoint类型参数可以决定是否执行目标方法
     * 环绕通知必须有返回值，返回值就是目标方法的返回值
     * @param joinPoint
     */
    /*
    @Around("execution(public int spring.aop.impl.ArithmeticCalculator.*(..))")
    public Object aroundMethod(ProceedingJoinPoint joinPoint){
        
        Object result=null;
        String methodName=joinPoint.getSignature().getName();
        try {
            //前置通知
            System.out.println("---->The method "+methodName+" begins with" +Arrays.asList(joinPoint.getArgs()));
            //执行目标方法
            result=joinPoint.proceed();
            //返回通知
            System.out.println("---->"+result);
        } catch (Throwable e) {
            e.printStackTrace();
            //异常通知
            System.out.println("---->"+e);
        }
        
        //后置通知
        System.out.println("---->The method "+methodName+ "ends");
        return result;
    }
    */
}

ApplicationContext.xml：

<?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:p="http://www.springframework.org/schema/p"
    xmlns:aop="http://www.springframework.org/schema/aop"
    xmlns:context="http://www.springframework.org/schema/context"
    xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-4.1.xsd
        http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-4.3.xsd
        http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop-4.3.xsd">
    
    <!-- 配置自动扫描的包 -->
    <context:component-scan base-package="spring.aop.impl"></context:component-scan>
    
    <aop:aspectj-autoproxy></aop:aspectj-autoproxy>
</beans>

测试：

package spring.aop.impl.test;

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

import spring.aop.impl.ArithmeticCalculator;

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(10, 20);
        System.out.println("result:"+result);
        
        result=arithmeticCalculator.div(10, 0);
        System.out.println("result:"+result);
    }

}

输出：

The method add begins [10, 20]
The method add ends 
The method add ends with afterReturning 30
result:30
The method div begins [10, 0]
The method div ends 
The method div occurs exection: java.lang.ArithmeticException: / by zero
Exception in thread "main" java.lang.ArithmeticException: / by zero
    at spring.aop.impl.ArithmeticCalculatorImpl.div(ArithmeticCalculatorImpl.java:24)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:497)
    at org.springframework.aop.support.AopUtils.invokeJoinpointUsingReflection(AopUtils.java:333)
    at org.springframework.aop.framework.ReflectiveMethodInvocation.invokeJoinpoint(ReflectiveMethodInvocation.java:190)
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:157)
    at org.springframework.aop.framework.adapter.MethodBeforeAdviceInterceptor.invoke(MethodBeforeAdviceInterceptor.java:52)
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179)
    at org.springframework.aop.aspectj.AspectJAfterAdvice.invoke(AspectJAfterAdvice.java:47)
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179)
    at org.springframework.aop.framework.adapter.AfterReturningAdviceInterceptor.invoke(AfterReturningAdviceInterceptor.java:52)
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179)
    at org.springframework.aop.aspectj.AspectJAfterThrowingAdvice.invoke(AspectJAfterThrowingAdvice.java:62)
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179)
    at org.springframework.aop.interceptor.ExposeInvocationInterceptor.invoke(ExposeInvocationInterceptor.java:92)
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179)
    at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:213)
    at com.sun.proxy.$Proxy12.div(Unknown Source)
    at spring.aop.impl.test.Main.main(Main.java:18)