返回通知，异常通知，环绕通知

看代码：

package logan.study.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);

}
package logan.study.aop.impl;

import org.springframework.stereotype.Component;

@Component

public class ArithmeticCalculatorImpl implements ArithmeticCalculator {

    @Override

    public int add(int i, int j) {

        // TODO Auto-generated method stub

        int result = i + j;

        return result;

    }

    @Override

    public int sub(int i, int j) {

        // TODO Auto-generated method stub

        int result = i - j;

        return result;

    }

    @Override

    public int mul(int i, int j) {

        // TODO Auto-generated method stub

        int result = i * j;

        return result;

    }

    @Override

    public int div(int i, int j) {

        // TODO Auto-generated method stub

        int result = i / j;

        return result;

    }

}
package logan.study.aop.impl;

import java.util.Arrays;

import java.util.List;

import org.aspectj.lang.JoinPoint;

import org.aspectj.lang.annotation.After;

import org.aspectj.lang.annotation.AfterReturning;

import org.aspectj.lang.annotation.AfterThrowing;

import org.aspectj.lang.annotation.Aspect;

import org.aspectj.lang.annotation.Before;

import org.springframework.stereotype.Component;

//把这个类声明为一个切面：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 {

    //声明该方法时一个前置通知：在目标方法开始之前执行

    @Before("execution(public int logan.study.aop.impl.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，在目标方法执行之后执行（无论该方法是否出现异常）

    //在后置通知中，还不能访问目标方法执行的结果，执行结果在返回通知中可以访问

    @After("execution(public int logan.study.aop.impl.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);

    }

    //返回通知，在方法正常结束时执行的代码

    //返回通知是可以访问返回值的

    @AfterReturning(value="execution(public int logan.study.aop.impl.ArithmeticCalculator.*(int, int))",

            returning="result")

    public void afterReturningMethod(JoinPoint joinPoint,Object result){

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

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

    }

    //异常通知，在方法抛出异常时调用

    @AfterThrowing(value="execution(public int logan.study.aop.impl.ArithmeticCalculator.*(int, int))",

            throwing="ex")

    public void afterThrowingMethod(JoinPoint joinPoint,Exception ex){

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

        System.out.println("The method "+ methodName +" occus with "+ex);

    }

}
<?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-4.3.xsd

        http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop-4.3.xsd">

    <context:component-scan base-package="logan.study.aop.impl"></context:component-scan>

    <aop:aspectj-autoproxy></aop:aspectj-autoproxy>

</beans>
package logan.study.aop.impl;

import org.springframework.context.ApplicationContext;

import org.springframework.context.support.ClassPathXmlApplicationContext;

public class Main {

    public static void main(String[] args) {

        // TODO Auto-generated method stub

        //1.创建Spring的IOC容器

        ApplicationContext ctx = new ClassPathXmlApplicationContext("applicationContext.xml");

        //2.从IOC容器里面获取bean实例

        ArithmeticCalculator arithmeticCalculator = ctx.getBean(ArithmeticCalculator.class);

        //使用Bean

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

        System.out.println(result);

        result = arithmeticCalculator.div(3, 0);

        System.out.println(result);

    }

}

执行结果：

五月 28, 2017 6:23:42 上午 org.springframework.context.support.ClassPathXmlApplicationContext prepareRefresh

信息: Refreshing org.springframework.context.support.ClassPathXmlApplicationContext@49c2faae: startup date [Sun May 28 06:23:42 CST 2017]; root of context hierarchy

五月 28, 2017 6:23:42 上午 org.springframework.beans.factory.xml.XmlBeanDefinitionReader loadBeanDefinitions

信息: Loading XML bean definitions from class path resource [applicationContext.xml]

The method add begins with [3, 6]

The method add ends with [3, 6]

The method add ends with 9

9

The method div begins with [3, 0]

The method div ends with [3, 0]

The method div occus with java.lang.ArithmeticException: / by zero

Exception in thread "main" java.lang.ArithmeticException: / by zero

    at logan.study.aop.impl.ArithmeticCalculatorImpl.div(ArithmeticCalculatorImpl.java:32)

    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:498)

    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.$Proxy10.div(Unknown Source)

    at logan.study.aop.impl.Main.main(Main.java:18)

在这里稍微改改代码：我们把异常改成空指针异常

package logan.study.aop.impl;

import java.util.Arrays;

import java.util.List;

import org.aspectj.lang.JoinPoint;

import org.aspectj.lang.annotation.After;

import org.aspectj.lang.annotation.AfterReturning;

import org.aspectj.lang.annotation.AfterThrowing;

import org.aspectj.lang.annotation.Aspect;

import org.aspectj.lang.annotation.Before;

import org.springframework.stereotype.Component;

//把这个类声明为一个切面：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 {

    //声明该方法时一个前置通知：在目标方法开始之前执行

    @Before("execution(public int logan.study.aop.impl.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，在目标方法执行之后执行（无论该方法是否出现异常）

    //在后置通知中，还不能访问目标方法执行的结果，执行结果在返回通知中可以访问

    @After("execution(public int logan.study.aop.impl.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);

    }

    //返回通知，在方法正常结束时执行的代码

    //返回通知是可以访问返回值的

    @AfterReturning(value="execution(public int logan.study.aop.impl.ArithmeticCalculator.*(int, int))",

            returning="result")

    public void afterReturningMethod(JoinPoint joinPoint,Object result){

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

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

    }

    //异常通知，在方法抛出异常时调用

    @AfterThrowing(value="execution(public int logan.study.aop.impl.ArithmeticCalculator.*(int, int))",

            throwing="ex")

    public void afterThrowingMethod(JoinPoint joinPoint,NullPointerException ex){

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

        System.out.println("The method "+ methodName +" occus with "+ex);

    }

}

执行结果：

五月 28, 2017 6:28:32 上午 org.springframework.context.support.ClassPathXmlApplicationContext prepareRefresh

信息: Refreshing org.springframework.context.support.ClassPathXmlApplicationContext@49c2faae: startup date [Sun May 28 06:28:32 CST 2017]; root of context hierarchy

五月 28, 2017 6:28:32 上午 org.springframework.beans.factory.xml.XmlBeanDefinitionReader loadBeanDefinitions

信息: Loading XML bean definitions from class path resource [applicationContext.xml]

The method add begins with [3, 6]

The method add ends with [3, 6]

The method add ends with 9

9

The method div begins with [3, 0]

The method div ends with [3, 0]

Exception in thread "main" java.lang.ArithmeticException: / by zero

    at logan.study.aop.impl.ArithmeticCalculatorImpl.div(ArithmeticCalculatorImpl.java:32)

    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:498)

    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.$Proxy10.div(Unknown Source)

    at logan.study.aop.impl.Main.main(Main.java:18)

可以看到异常通知没有执行。只有当发生空指针异常时才会执行。

下面看环绕通知：

package logan.study.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.springframework.stereotype.Component;

//把这个类声明为一个切面：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 {

    /**

     * 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，返回值即为目标方法的返回值

     */

    @Around("execution(public int logan.study.aop.impl.ArithmeticCalculator.*(int, int))")

    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();

            //返回通知

            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;

    }

}
package logan.study.aop.impl;

import org.springframework.context.ApplicationContext;

import org.springframework.context.support.ClassPathXmlApplicationContext;

public class Main {

    public static void main(String[] args) {

        // TODO Auto-generated method stub

        //1.创建Spring的IOC容器

        ApplicationContext ctx = new ClassPathXmlApplicationContext("applicationContext.xml");

        //2.从IOC容器里面获取bean实例

        ArithmeticCalculator arithmeticCalculator = ctx.getBean(ArithmeticCalculator.class);

        //使用Bean

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

        System.out.println(result);

        result = arithmeticCalculator.div(3, 0);

        System.out.println(result);

    }

}

返回结果：

五月 28, 2017 6:51:09 上午 org.springframework.context.support.ClassPathXmlApplicationContext prepareRefresh

信息: Refreshing org.springframework.context.support.ClassPathXmlApplicationContext@49c2faae: startup date [Sun May 28 06:51:09 CST 2017]; root of context hierarchy

五月 28, 2017 6:51:09 上午 org.springframework.beans.factory.xml.XmlBeanDefinitionReader loadBeanDefinitions

信息: Loading XML bean definitions from class path resource [applicationContext.xml]

The methodadd begins with [3, 6]

The methodadd ends with 9

The method addends

9

The methoddiv begins with [3, 0]

The method occurs exception:java.lang.ArithmeticException: / by zero

The method divends

Exception in thread "main" org.springframework.aop.AopInvocationException: Null return value from advice does not match primitive return type for: public abstract int logan.study.aop.impl.ArithmeticCalculator.div(int,int)

    at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:227)

    at com.sun.proxy.$Proxy7.div(Unknown Source)

    at logan.study.aop.impl.Main.main(Main.java:18)

环绕通知一般来说不常用。

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