Spring入门第二十课

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。