Autowiring unable to find generic dependency in case of nested unresolved type variable [SPR-11471]

[spring-projects-issues]

Jair da Silva Ferreira Júnior opened SPR-11471 and commented

Hi,
I believe I found an issue with autowiring and generics.
I attached a simple eclipse example project to show you the issue.

Here is my "application-context.xml" file:

<?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"
	xsi:schemaLocation="http://www.springframework.org/schema/beans
         http://www.springframework.org/schema/beans/spring-beans-3.2.xsd
         http://www.springframework.org/schema/context
         http://www.springframework.org/schema/context/spring-context-3.2.xsd">

	<context:annotation-config/>
	
	<bean class="spring.test.generics.GenericInterface1Impl" factory-method="create"/>
	<bean class="spring.test.generics.GenericInterface2Impl"/>
</beans>

I have 2 classes: "GenericInterface1Impl" and "GenericInterface2Impl".
"GenericInterface1Impl" depends on an implementation of "GenericInterface2".

public class GenericInterface1Impl<T> implements GenericInterface1<T>{

	@Autowired
	private GenericInterface2<T> gi2;

	@Override
	public String doSomethingGeneric(T o) {
		return gi2.doSomethingMoreGeneric(o) + "_somethingGeneric_" + o;
	}
	
	/**
	 * Factory Method
	 * @return an instance of <code>GenericInterface1<String></code>
	 */
	public static GenericInterface1<String> create(){
		return new GenericInterface1Impl<>();
	}

}

public class GenericInterface2Impl implements GenericInterface2<String>{

	@Override
	public String doSomethingMoreGeneric(String o) {
		return "somethingMoreGeneric_" + o;
	}
}

"GenericInterface1Impl" has a factory method that creates an instance of "GenericInterface1<String>".

The issue is: spring can't find a qualifying bean for the attribute "GenericInterface1.gi2" even though there's a suitable "GenericInterface2<String>" implementation (GenericInterface2Impl) in the application context.

The exact same code works perfectly with spring version 3.2.8 but fails with spring version 4.0.2. You can easily change the spring version to 3.2.8 in "pom.xml" to verify that.

Here's the exception stack trace:

Exception in thread "main" org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'spring.test.generics.GenericInterface1Impl#0': Injection of autowired dependencies failed; nested exception is org.springframework.beans.factory.BeanCreationException: Could not autowire field: private spring.test.generics.GenericInterface2 spring.test.generics.GenericInterface1Impl.gi2; nested exception is org.springframework.beans.factory.NoSuchBeanDefinitionException: No qualifying bean of type [spring.test.generics.GenericInterface2] 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)}
	at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor.postProcessPropertyValues(AutowiredAnnotationBeanPostProcessor.java:292)
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.populateBean(AbstractAutowireCapableBeanFactory.java:1185)
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:537)
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:475)
	at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:304)
	at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:228)
	at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:300)
	at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:195)
	at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:700)
	at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:760)
	at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:482)
	at org.springframework.context.support.ClassPathXmlApplicationContext.<init>(ClassPathXmlApplicationContext.java:139)
	at org.springframework.context.support.ClassPathXmlApplicationContext.<init>(ClassPathXmlApplicationContext.java:83)
	at spring.test.generics.App.main(App.java:13)
Caused by: org.springframework.beans.factory.BeanCreationException: Could not autowire field: private spring.test.generics.GenericInterface2 spring.test.generics.GenericInterface1Impl.gi2; nested exception is org.springframework.beans.factory.NoSuchBeanDefinitionException: No qualifying bean of type [spring.test.generics.GenericInterface2] found for dependency: expected at least 1 bean which qualifies as autowire candidate for this dependency. Dependency annotations: {@org.springframework.beans.factory.annotation.Autowired(required=true)}
	at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor$AutowiredFieldElement.inject(AutowiredAnnotationBeanPostProcessor.java:508)
	at org.springframework.beans.factory.annotation.InjectionMetadata.inject(InjectionMetadata.java:87)
	at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor.postProcessPropertyValues(AutowiredAnnotationBeanPostProcessor.java:289)
	... 13 more
Caused by: org.springframework.beans.factory.NoSuchBeanDefinitionException: No qualifying bean of type [spring.test.generics.GenericInterface2] 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)}
	at org.springframework.beans.factory.support.DefaultListableBeanFactory.raiseNoSuchBeanDefinitionException(DefaultListableBeanFactory.java:1100)
	at org.springframework.beans.factory.support.DefaultListableBeanFactory.doResolveDependency(DefaultListableBeanFactory.java:960)
	at org.springframework.beans.factory.support.DefaultListableBeanFactory.resolveDependency(DefaultListableBeanFactory.java:855)
	at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor$AutowiredFieldElement.inject(AutowiredAnnotationBeanPostProcessor.java:480)
	... 15 more

Thanks,
Jair Jr

---

Affects: 4.0.2

Attachments:

• spring-generics-test.zip (9.00 kB)

Issue Links:

• Autowiring unable to find generic dependency [SPR-11529] #16154 Autowiring unable to find generic dependency
• Introspect factory method return type for type variable resolution at injection points [SPR-11521] #16146 Introspect factory method return type for type variable resolution at injection points

Referenced from: commits spring-projects/spring-session@0abbba0

0 votes, 6 watchers

[spring-projects-issues]

Juergen Hoeller commented

I have a solution for the immediate regression here in the meantime, allowing a match against a nested unresolvable type variable. This is equivalent to Spring 3.2.x's behavior again, and therefore sufficient for this issue to be considered as resolved. To be committed tomorrow.

However, there is a related limitation of a more general kind: We only evaluate generic type information at the factory method return type level for matching target beans but not for substituting type variables at injection points themselves. In the present case, we don't detect the String substitute in the create() method signature and therefore behave like the type variable remains unresolved when trying to inject the field. We should revisit our resolution mechanism there for 4.1, with a follow-up JIRA issue tracking that part of the story.

Juergen

[spring-projects-issues]

Jair da Silva Ferreira Júnior commented

Thank you very much!
It works now!

Jair