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使用Spring AOP引入新功能

javaspringaop
4
我正在使用《Spring实战（第3版）》学习Spring。在书中，我遇到了一个示例无法正常工作的问题，以下是详细信息：
我试图使用Spring AOP在bean中引入新功能：
类结构如下：
1. Instrumentalist实现Performer 2. GraciousContestant实现Contestant
Performer接口
public interface Performer {
    void perform();
}

乐器演奏家课程

package chapter4;

public class Instrmentalist implements Performer {
    public void perform() {
        System.out.println("Sining hey hey, hey");
    }
}

竞赛选手界面

package chapter4;

public interface Contestant {
    void receiveAward();
}

亲切的Contestant类

package chapter4;

public class GraciousContestant implements Contestant {
    public void receiveAward() {
        System.out.println("Won a car worth 4K!");
    }
}

我的Spring配置文件称为“spring-idol2.xml”，如下所示：

<?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: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-3.1.xsd
        http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop-3.1.xsd
        http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-3.1.xsd">

    <bean id="ken" class="chapter4.Instrmentalist" />

    <bean id="contestantDelegate" class="chapter4.GraciousContestant" />

    <aop:config>
        <aop:aspect>
            <aop:declare-parents 
            types-matching="chapter4.Performer+" 
            implement-interface="chapter4.Contestant"
            delegate-ref="contestantDelegate"/>
        </aop:aspect>

        <aop:aspect ref="ken">
            <aop:pointcut id="performance"
                    expression="execution(* chapter4.Performer.perform(..))" />
            <aop:after pointcut-ref="performance" method="receiveAward"/>       
    </aop:aspect>
    </aop:config>
</beans>

我的Main方法看起来像这样:

package chapter4;

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

public class TestMain {
    public static void main(String[] args) {
        AbstractApplicationContext context =
                new ClassPathXmlApplicationContext("/chapter4/spring-idol2.xml");

        Performer p1 = (Performer) context.getBean("ken");      
        p1.perform();
    }
}

应该打印出的内容如下：
Sining hey hey, hey
Won a car worth 4K!

然而我遇到了以下错误：
Exception in thread "main" org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'ken' defined in class path resource [chapter4/spring-idol2.xml]: BeanPostProcessor before instantiation of bean failed; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'org.springframework.aop.aspectj.DeclareParentsAdvisor#0': Cannot resolve reference to bean 'contestantDelegate' while setting constructor argument; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'contestantDelegate' defined in class path resource [chapter4/spring-idol2.xml]: BeanPostProcessor before instantiation of bean failed; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'org.springframework.aop.aspectj.AspectJPointcutAdvisor#0': Cannot create inner bean '(inner bean)' of type [org.springframework.aop.aspectj.AspectJAfterAdvice] while setting constructor argument; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name '(inner bean)': Cannot create inner bean '(inner bean)' of type [org.springframework.aop.config.MethodLocatingFactoryBean] while setting constructor argument; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name '(inner bean)': Initialization of bean failed; nested exception is java.lang.IllegalArgumentException: Unable to locate method [receiveAward] on bean [ken]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:452)
    at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:295)
    at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:222)
    at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:292)
    at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:194)
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:580)
    at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:900)
    at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:455)
    at org.springframework.context.support.ClassPathXmlApplicationContext.<init>(ClassPathXmlApplicationContext.java:139)
    at org.springframework.context.support.ClassPathXmlApplicationContext.<init>(ClassPathXmlApplicationContext.java:83)
    at chapter4.TestMain.main(TestMain.java:13)
Caused by: org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'org.springframework.aop.aspectj.DeclareParentsAdvisor#0': Cannot resolve reference to bean 'contestantDelegate' while setting constructor argument; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'contestantDelegate' defined in class path resource [chapter4/spring-idol2.xml]: BeanPostProcessor before instantiation of bean failed; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'org.springframework.aop.aspectj.AspectJPointcutAdvisor#0': Cannot create inner bean '(inner bean)' of type [org.springframework.aop.aspectj.AspectJAfterAdvice] while setting constructor argument; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name '(inner bean)': Cannot create inner bean '(inner bean)' of type [org.springframework.aop.config.MethodLocatingFactoryBean] while setting constructor argument; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name '(inner bean)': Initialization of bean failed; nested exception is java.lang.IllegalArgumentException: Unable to locate method [receiveAward] on bean [ken]
    at org.springframework.beans.factory.support.BeanDefinitionValueResolver.resolveReference(BeanDefinitionValueResolver.java:328)
    at org.springframework.beans.factory.support.BeanDefinitionValueResolver.resolveValueIfNecessary(BeanDefinitionValueResolver.java:106)
    at org.springframework.beans.factory.support.ConstructorResolver.resolveConstructorArguments(ConstructorResolver.java:616)
    at org.springframework.beans.factory.support.ConstructorResolver.autowireConstructor(ConstructorResolver.java:148)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.autowireConstructor(AbstractAutowireCapableBeanFactory.java:1003)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBeanInstance(AbstractAutowireCapableBeanFactory.java:907)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:485)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:456)
    at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:295)
    at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:222)
    at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:292)
    at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:198)
    at org.springframework.aop.framework.autoproxy.BeanFactoryAdvisorRetrievalHelper.findAdvisorBeans(BeanFactoryAdvisorRetrievalHelper.java:86)
    at org.springframework.aop.framework.autoproxy.AbstractAdvisorAutoProxyCreator.findCandidateAdvisors(AbstractAdvisorAutoProxyCreator.java:100)
    at org.springframework.aop.aspectj.autoproxy.AspectJAwareAdvisorAutoProxyCreator.shouldSkip(AspectJAwareAdvisorAutoProxyCreator.java:107)
    at org.springframework.aop.framework.autoproxy.AbstractAutoProxyCreator.postProcessBeforeInstantiation(AbstractAutoProxyCreator.java:278)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.applyBeanPostProcessorsBeforeInstantiation(AbstractAutowireCapableBeanFactory.java:848)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.resolveBeforeInstantiation(AbstractAutowireCapableBeanFactory.java:820)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:446)
    ... 10 more
Caused by: org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'contestantDelegate' defined in class path resource [chapter4/spring-idol2.xml]: BeanPostProcessor before instantiation of bean failed; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'org.springframework.aop.aspectj.AspectJPointcutAdvisor#0': Cannot create inner bean '(inner bean)' of type [org.springframework.aop.aspectj.AspectJAfterAdvice] while setting constructor argument; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name '(inner bean)': Cannot create inner bean '(inner bean)' of type [org.springframework.aop.config.MethodLocatingFactoryBean] while setting constructor argument; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name '(inner bean)': Initialization of bean failed; nested exception is java.lang.IllegalArgumentException: Unable to locate method [receiveAward] on bean [ken]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:452)
    at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:295)
    at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:222)
    at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:292)
    at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:194)
    at org.springframework.beans.factory.support.BeanDefinitionValueResolver.resolveReference(BeanDefinitionValueResolver.java:322)
    ... 28 more
Caused by: org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'org.springframework.aop.aspectj.AspectJPointcutAdvisor#0': Cannot create inner bean '(inner bean)' of type [org.springframework.aop.aspectj.AspectJAfterAdvice] while setting constructor argument; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name '(inner bean)': Cannot create inner bean '(inner bean)' of type [org.springframework.aop.config.MethodLocatingFactoryBean] while setting constructor argument; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name '(inner bean)': Initialization of bean failed; nested exception is java.lang.IllegalArgumentException: Unable to locate method [receiveAward] on bean [ken]
    at org.springframework.beans.factory.support.BeanDefinitionValueResolver.resolveInnerBean(BeanDefinitionValueResolver.java:281)
    at org.springframework.beans.factory.support.BeanDefinitionValueResolver.resolveValueIfNecessary(BeanDefinitionValueResolver.java:125)
    at org.springframework.beans.factory.support.ConstructorResolver.resolveConstructorArguments(ConstructorResolver.java:630)
    at org.springframework.beans.factory.support.ConstructorResolver.autowireConstructor(ConstructorResolver.java:148)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.autowireConstructor(AbstractAutowireCapableBeanFactory.java:1003)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBeanInstance(AbstractAutowireCapableBeanFactory.java:907)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:485)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:456)
    at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:295)
    at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:222)
    at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:292)
    at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:198)
    at org.springframework.aop.framework.autoproxy.BeanFactoryAdvisorRetrievalHelper.findAdvisorBeans(BeanFactoryAdvisorRetrievalHelper.java:86)
    at org.springframework.aop.framework.autoproxy.AbstractAdvisorAutoProxyCreator.findCandidateAdvisors(AbstractAdvisorAutoProxyCreator.java:100)
    at org.springframework.aop.aspectj.autoproxy.AspectJAwareAdvisorAutoProxyCreator.shouldSkip(AspectJAwareAdvisorAutoProxyCreator.java:107)
    at org.springframework.aop.framework.autoproxy.AbstractAutoProxyCreator.postProcessBeforeInstantiation(AbstractAutoProxyCreator.java:278)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.applyBeanPostProcessorsBeforeInstantiation(AbstractAutowireCapableBeanFactory.java:848)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.resolveBeforeInstantiation(AbstractAutowireCapableBeanFactory.java:820)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:446)
    ... 33 more
Caused by: org.springframework.beans.factory.BeanCreationException: Error creating bean with name '(inner bean)': Cannot create inner bean '(inner bean)' of type [org.springframework.aop.config.MethodLocatingFactoryBean] while setting constructor argument; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name '(inner bean)': Initialization of bean failed; nested exception is java.lang.IllegalArgumentException: Unable to locate method [receiveAward] on bean [ken]
    at org.springframework.beans.factory.support.BeanDefinitionValueResolver.resolveInnerBean(BeanDefinitionValueResolver.java:281)
    at org.springframework.beans.factory.support.BeanDefinitionValueResolver.resolveValueIfNecessary(BeanDefinitionValueResolver.java:125)
    at org.springframework.beans.factory.support.ConstructorResolver.resolveConstructorArguments(ConstructorResolver.java:616)
    at org.springframework.beans.factory.support.ConstructorResolver.autowireConstructor(ConstructorResolver.java:148)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.autowireConstructor(AbstractAutowireCapableBeanFactory.java:1003)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBeanInstance(AbstractAutowireCapableBeanFactory.java:907)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:485)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:456)
    at org.springframework.beans.factory.support.BeanDefinitionValueResolver.resolveInnerBean(BeanDefinitionValueResolver.java:270)
    ... 51 more
Caused by: org.springframework.beans.factory.BeanCreationException: Error creating bean with name '(inner bean)': Initialization of bean failed; nested exception is java.lang.IllegalArgumentException: Unable to locate method [receiveAward] on bean [ken]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:527)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:456)
    at org.springframework.beans.factory.support.BeanDefinitionValueResolver.resolveInnerBean(BeanDefinitionValueResolver.java:270)
    ... 59 more
Caused by: java.lang.IllegalArgumentException: Unable to locate method [receiveAward] on bean [ken]
    at org.springframework.aop.config.MethodLocatingFactoryBean.setBeanFactory(MethodLocatingFactoryBean.java:75)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.invokeAwareMethods(AbstractAutowireCapableBeanFactory.java:1440)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1408)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:519)
    ... 61 more

请问为什么会出现“无法在bean [ken]上找到[receiveAward]方法”的提示，即使我已经声明了一个父类？语法有误吗？

非常感谢您的帮助，

祝好，

Khush。

异常信息中有这样一句话：**无法在bean [ken]上找到方法[receiveAward]**。 - d-live
@d-live 但是那个异常不应该出现，因为我已经将Contestant声明为父类。 - Khush
2个回答
6
请注意，<aop:config> 在应用方面之前看到 bean，因此我猜在其他切面声明中不能使用<aop:declare-parents>引入的方法。
如果您想检查<aop:declare-parents>是否起作用，可以像这样操作：
Performer p1 = (Performer) context.getBean("ken"); 
p1.perform();
((Contestant) p1).reveiveAward();
感谢您抽出时间回答我的问题，您的解释非常有价值。我非常感激您的帮助。 - Khush
0

我认为当你写代码时

<aop:aspect ref="ken">
    ...
</aop:aspect>

你的意思是方面在名为“ken”的bean中实现。但在你的例子中并非如此，方面在“contestantDelegate” bean中。因此，我会尝试使用以下代码：

<aop:aspect ref="contestantDelegate">
    ...
</aop:aspect>
但是因为我们将Contestant声明为父类，难道我们不应该能够调用receiveAward方法吗？毕竟我们正在尝试使用Spring AOP引入新的功能？ - Khush
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