自动将混凝土类装配到抽象装饰器中

Question

Greetings ladies and gents,

I'm implementing a system where we are trying to keep things highly flexible. We have an abstract superclass called EmailTaskService which has two classes inheriting from it. One is EmailTaskServiceImpl (the concrete implementation class), and the other is another abstract class called ScheduledEmailTaskService which has a subclass called ScheduledEmailTaskServiceImpl .

To keep things flexible, we are using both a vertical and horizontal decorator pattern on the ScheduledEmailTaskService . This means that it inherits from EmailTaskService as well as composing in the concrete service itself. But my problem comes from trying to autowire the concrete EmailTaskServiceImpl , all I get is a No qualifying bean of type EmailTaskServiceImpl exception thrown. Obviously I can't just autowire EmailTaskService because its an abstract class, not an interface.

I'll post the code below to give you an idea of what is going on.

public abstract class EmailTaskService<E, I> implements GenericService<E, I>{

    @Autowired
    protected EmailTaskDAO emailTaskDao;

    public abstract void deleteEmailTask(I emailTaskId);

}

@Service("emailTaskService")
public class EmailTaskServiceImpl extends EmailTaskService<EmailTask, Long>{

    @Override
    @Transactional
    public long getTotalObjects() {
        return super.emailTaskDao.count();
    }
    etc etc other methods here doing concretey things.

public abstract class ScheduledEmailTaskService<E, I> extends EmailTaskService<E, I> {

    @Autowired
    protected ScheduledEmailTaskDAO scheduledEmailTaskDao;
    @Autowired
    @Qualifier("emailTaskService")
    protected EmailTaskService<EmailTask, Long> emailTaskService;

    @Override
    public abstract void deleteEmailTask(I emailTaskId) throws InvalidInvocationException;

    public abstract void deleteScheduledEmailTask(I scheduledEmailTaskId);
}

@Service
public class ScheduledEmailTaskServiceImpl extends ScheduledEmailTaskService<ScheduledEmailTask, Long> {

    @Override
    @Transactional
    public long getTotalObjects() {
        return super.scheduledEmailTaskDao.count();
    }

    more concretey methods go here

In case you are wondering GenericService<E, I> is an interface that specifies CRUD methods for all my services to implement which is why EmailTaskService implements it.

So my question is how do I get some sort of reference to EmailTaskService or EmailTaskServiceImpl successfully available in ScheduledEmailTaskService either through Autowiring or through another sensible method. If this just isn't possible, Why?

EDIT 1 (Context Configuration): Ask and ye shall receive:

<beans Spring namespace config etc etc etc>
<context:component-scan base-package="au.com.mail" />

<mvc:annotation-driven />

<tx:annotation-driven />

<task:annotation-driven/>

<!-- Project Properties -->
<bean class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer">
    <property name="locations">
        <value>classpath:project.properties</value>
    </property>
</bean> 
</beans>

EDIT 2: Actual Proper Stacktrace:

[junit] Caused by: org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'scheduledEmailTaskServiceImpl': Injection of autowired dependencies failed; nested exception is org.springframework.beans.factory.BeanCreationException: Could not autowire field: protected au.com.mail.service.emailtask.EmailTaskService au.com.mail.service.emailtask.ScheduledEmailTaskService.emailTaskService; nested exception is org.springframework.beans.factory.NoSuchBeanDefinitionException: No qualifying bean of type [au.com.mail.service.emailtask.EmailTaskService] found for dependency: expected at least 1 bean which qualifies as autowire candidate for this dependency. Dependency annotations: {@org.springframework.beans.factory.annotation.Autowired(required=true), @org.springframework.beans.factory.annotation.Qualifier(value=emailTaskService)}
[junit]     at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor.postProcessPropertyValues(AutowiredAnnotationBeanPostProcessor.java:289)
[junit]     at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.populateBean(AbstractAutowireCapableBeanFactory.java:1146)
[junit]     at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:519)
[junit]     at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:458)
[junit]     at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:296)
[junit]     at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:223)
[junit]     at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:293)
[junit]     at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:194)
[junit]     at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:628)
[junit]     at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:932)
[junit]     at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:479)
[junit]     at org.springframework.test.context.support.AbstractGenericContextLoader.loadContext(AbstractGenericContextLoader.java:120)
[junit]     at org.springframework.test.context.support.AbstractGenericContextLoader.loadContext(AbstractGenericContextLoader.java:60)
[junit]     at org.springframework.test.context.support.AbstractDelegatingSmartContextLoader.delegateLoading(AbstractDelegatingSmartContextLoader.java:100)
[junit]     at org.springframework.test.context.support.AbstractDelegatingSmartContextLoader.loadContext(AbstractDelegatingSmartContextLoader.java:248)
[junit]     at org.springframework.test.context.CacheAwareContextLoaderDelegate.loadContextInternal(CacheAwareContextLoaderDelegate.java:64)
[junit]     at org.springframework.test.context.CacheAwareContextLoaderDelegate.loadContext(CacheAwareContextLoaderDelegate.java:91)
[junit]     ... 50 more
[junit] Caused by: org.springframework.beans.factory.BeanCreationException: Could not autowire field: protected au.com.mail.service.emailtask.EmailTaskService au.com.mail.service.emailtask.ScheduledEmailTaskService.emailTaskService; nested exception is org.springframework.beans.factory.NoSuchBeanDefinitionException: No qualifying bean of type [au.com.mail.service.emailtask.EmailTaskService] found for dependency: expected at least 1 bean which qualifies as autowire candidate for this dependency. Dependency annotations: {@org.springframework.beans.factory.annotation.Autowired(required=true), @org.springframework.beans.factory.annotation.Qualifier(value=emailTaskService)}
[junit]     at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor$AutowiredFieldElement.inject(AutowiredAnnotationBeanPostProcessor.java:517)
[junit]     at org.springframework.beans.factory.annotation.InjectionMetadata.inject(InjectionMetadata.java:87)
[junit]     at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor.postProcessPropertyValues(AutowiredAnnotationBeanPostProcessor.java:286)
[junit]     ... 66 more
[junit] Caused by: org.springframework.beans.factory.NoSuchBeanDefinitionException: No qualifying bean of type [au.com.mail.service.emailtask.EmailTaskService] found for dependency: expected at least 1 bean which qualifies as autowire candidate for this dependency. Dependency annotations: {@org.springframework.beans.factory.annotation.Autowired(required=true), @org.springframework.beans.factory.annotation.Qualifier(value=emailTaskService)}
[junit]     at org.springframework.beans.factory.support.DefaultListableBeanFactory.raiseNoSuchBeanDefinitionException(DefaultListableBeanFactory.java:988)
[junit]     at org.springframework.beans.factory.support.DefaultListableBeanFactory.doResolveDependency(DefaultListableBeanFactory.java:858)
[junit]     at org.springframework.beans.factory.support.DefaultListableBeanFactory.resolveDependency(DefaultListableBeanFactory.java:770)
[junit]     at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor$AutowiredFieldElement.inject(AutowiredAnnotationBeanPostProcessor.java:489)
[junit]     ... 68 more

And before you ask, yes my JUnit is configured to use the Spring Application Context correctly.

Answer 1

Given that you have @Transactional everywhere, I'm going to assume you have some proxying going on with JDK proxies.

As it turns out, JKD proxies can only get your target bean's interfaces, not their class hierarchy. So the proxy created for your EmailTaskServiceImpl is not of type EmailTaskServiceImpl and can therefore not fill in for an injection target of that type. Instead, it is of type EmailTaskService , but your field is

@Autowired
protected EmailTaskServiceImpl emailTaskService;

so that won't do.

There are two solutions:

The first is to change your configuration to use CGLIB proxies. You'll need to change your transactional configuration to

<tx:annotation-driven proxy-target-class="true" />

and add the CGLIB libraries to your classpath.

The second is to change your field to

@Autowired
@Qualifier("someName")
protected EmailTaskService emailTaskService;

and your class declaration to

@Service("someName")
public class EmailTaskServiceImpl extends EmailTaskService<EmailTask, Long>{

Spring will use the name instead of the type when determining which bean to inject. This is necessary because you have many EmailTaskService candidate beans.