Stuck on AOP with AspectJ/Java

[Mark Arsenault]

I've been looking forward to posting on the Big Moose Saloon, need help, probably something simple I'm missing...

I am working through Spring Into Action 3, on page 132 (4.5 of that unit) I'm working through an Aspect J example.

This is made up of 4 different file, CriticismEngine(Interface), CriticismEngineImpl(implmentation), JudgeAspect(AspectJ Aspect), Preformance(contains main method), and my Spring configuration, spring-idol.xml

here is the Error:

Dec 19, 2013 12:18:12 PM org.springframework.context.support.AbstractApplicationContext prepareRefresh
INFO: Refreshing org.springframework.context.support.ClassPathXmlApplicationContext@7994d431: startup date [Thu Dec 19 12:18:12 EST 2013]; root of context hierarchy
Dec 19, 2013 12:18:12 PM org.springframework.beans.factory.xml.XmlBeanDefinitionReader loadBeanDefinitions
INFO: Loading XML bean definitions from class path resource [spring-idol.xml]
Dec 19, 2013 12:18:13 PM org.springframework.beans.factory.support.DefaultListableBeanFactory preInstantiateSingletons
INFO: Pre-instantiating singletons in org.springframework.beans.factory.support.DefaultListableBeanFactory@22a668fd: defining beans [criticismEngine,org.sia.springidol.JudgeAspect#0,guitar,eddie]; root of factory hierarchy
Dec 19, 2013 12:18:13 PM org.springframework.beans.factory.support.DefaultSingletonBeanRegistry destroySingletons
INFO: Destroying singletons in org.springframework.beans.factory.support.DefaultListableBeanFactory@22a668fd: defining beans [criticismEngine,org.sia.springidol.JudgeAspect#0,guitar,eddie]; root of factory hierarchy
Exception in thread "main" org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'criticismEngine' defined in class path resource [spring-idol.xml]: Error setting property values; nested exception is org.springframework.beans.NotWritablePropertyException: Invalid property 'criticisms' of bean class [org.sia.springidol.CriticismEngineImpl]: Bean property 'criticisms' is not writable or has an invalid setter method. Does the parameter type of the setter match the return type of the getter?
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.applyPropertyValues(AbstractAutowireCapableBeanFactory.java:1423)
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.populateBean(AbstractAutowireCapableBeanFactory.java:1128)
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:519)
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:458)
	at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:295)
	at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:223)
	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:626)
	at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:932)
	at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:479)
	at org.springframework.context.support.ClassPathXmlApplicationContext.<init>(ClassPathXmlApplicationContext.java:139)
	at org.springframework.context.support.ClassPathXmlApplicationContext.<init>(ClassPathXmlApplicationContext.java:83)
	at org.sia.springidol.Preformance.main(Preformance.java:10)
Caused by: org.springframework.beans.NotWritablePropertyException: Invalid property 'criticisms' of bean class [org.sia.springidol.CriticismEngineImpl]: Bean property 'criticisms' is not writable or has an invalid setter method. Does the parameter type of the setter match the return type of the getter?
	at org.springframework.beans.BeanWrapperImpl.setPropertyValue(BeanWrapperImpl.java:1042)
	at org.springframework.beans.BeanWrapperImpl.setPropertyValue(BeanWrapperImpl.java:902)
	at org.springframework.beans.AbstractPropertyAccessor.setPropertyValues(AbstractPropertyAccessor.java:75)
	at org.springframework.beans.AbstractPropertyAccessor.setPropertyValues(AbstractPropertyAccessor.java:57)
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.applyPropertyValues(AbstractAutowireCapableBeanFactory.java:1420)
	... 13 more

Now the four files:

CriticismEngine:

package org.sia.springidol;

public interface CriticismEngine {
	
	public String getCriticism();
	

}

CriticismEngineImpl.java:

package org.sia.springidol;

public class CriticismEngineImpl implements CriticismEngine {
	
	public CriticismEngineImpl() {}
	
	public String getCriticism() {
		int i = (int) (Math.random() * criticismPool.length);
		return criticismPool[i];
	}
	
	// Injected
	private String[] criticismPool;
	public void setCriticismPool(String[] criticismPool)  {
		this.criticismPool = criticismPool;
	}

}

JudgeAspect.aj:

package org.sia.springidol;

public aspect JudgeAspect {
	public JudgeAspect() {}
	
	pointcut preformance() : execution(* org.sia.springidol.Preformer.preform(..));
	
	after() returning() : preformance() {
		System.out.println(criticismEngine.getCriticism());
	}
	
	// Injected
	private CriticismEngine criticismEngine;
	public void setCriticismEngine(CriticismEngine criticismEngine) {
		this.criticismEngine = criticismEngine;
	}
}

Preformance:

package org.sia.springidol;

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

public class Preformance {

	public static void main(String[] args) {
		ApplicationContext context = new ClassPathXmlApplicationContext("spring-idol.xml");
		
		Preformer preformer = (Preformer) context.getBean("eddie");
		preformer.preform();
		((ConfigurableApplicationContext)context).close();

	}

}

and now my Spring configuration XML:

<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"
xsi:schemaLocation="http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans-3.0.xsd
http://www.springframework.org/schema/aop
http://www.springframework.org/schema/aop/spring-aop-3.0.xsd">


<bean id="criticismEngine" class="org.sia.springidol.CriticismEngineImpl">
	<property name="criticisms">
		<list>
			<value>This song sucks!</value>
			<value>This song sucks more!</value>
			<value>This song sucks the worst!</value>
		</list>
	</property>
</bean>
		
		<bean class="org.sia.springidol.JudgeAspect" factory-method="aspectOf" >
			<property name="criticismEngine" ref="criticismEngine" />
		</bean>
		
		
<!-- 		REGULAR GETTER SETTER INJECTION WITHOUT ANNOTATION OR AUTOWIRING -->
		<bean id="guitar" class="org.sia.springidol.Guitar" />
		
		<bean id="eddie" class="org.sia.springidol.Instrumentalist" >
			<property name="instrument" ref="guitar" />
			<property name="song" value="Go fuck yourself!" />
		</bean>
</beans>

So, basically, when the bean with ID eddie preforms (that part of program works fine, just does a println of property values listed, criticismEngine is supposed to write criticism after the "preformance".

Let me know if anything else is needed, thanks!

Thanks!

[Bill Gorder]

looks like the problem lies here:

<bean id="criticismEngine" class="org.sia.springidol.CriticismEngineImpl">  
    <property name="criticisms">  
        <list>  
            <value>This song sucks!</value>  
            <value>This song sucks more!</value>  
            <value>This song sucks the worst!</value>  
        </list>  
    </property>  
</bean>  

This is saying that there is a property on CriticismEngineImpl, called criticisms and you want to set a List<String> on it. So it expects the following:

package org.sia.springidol;

public class CriticismEngineImpl implements CriticismEngine {
	
	public CriticismEngineImpl() {}
	
	public String getCriticism() {
		int i = (int) (Math.random() * criticisms.size());
		return criticisms.get(i);
	}
	
	// Injected
	private List<String> criticisms;
	public void setCriticisms(List<String> criticisms)  {
		this.criticisms = criticisms;
	}

}

You could actually leave it as a String[] if you wanted to and it should still work. Spring will figure it out. The reason it was failing is the setter name needs to match the property in the XML (minus the 'set' prefix)

[Mark Arsenault]

Wow, I feel foolish for even asking a question with such a simple answer. The problem here was tunnel vision, the originally posted code was almost a direct copy from the book, this is the third error I have found in this book. I defined the property in the configuration file, obviously I need to inject those values, but for some reason I just didn't connect it.

Thank you very much,

Mark