MongoEventListener: unresolvable circular reference when referencing mongoTemplate

[johannz]

I am trying to use the Mongo Lifecycle Event support provided by Spring Data ( http://static.springsource.org/sprin...g-usage.events ) and am having problems when I attempt to have my event listener be injected with a reference to either a mongoTemplate or a repository object; it throws BeanCreationExceptions.

As an example, here is part of one of my listeners. It is supposed to auto-populate a field before saving the visitor object by looking up some data.

The only way I've gotten this to work was to not use bean injection on my EventListener. Instead I had it be ApplicationContextAware, and looked up the objects from the context right before I called them. This kind of defeats the purpose of using DI, so I'm not happy with it. Any suggestions?

public class VisitorMongoEventListener extends AbstractMongoEventListener<Visitor> {
	@Autowired
	private MongoTemplate mongoTemplate; // This line causes it to fail

	@Autowired
	private VisitorRepository visitorRepository; // This line also causes it to fail

	@Override
	public void onBeforeConvert(Visitor source) {
		if (StringUtils.isBlank(source.setEmbeddedValue())) {
			String value= visitorRepository.lookupSomeOtherValueToEmbed(source);
			source.setEmbeddedValue(value);
		}
	}

and it throws the following exception stack.

ERROR [2011-09-28 16:37:26,944] [Thread-1] (ContextLoader.java:227) - Context initialization failed
org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'mongoTemplate' defined in class path resource [application-mongo.xml]: Cannot resolve reference to bean 'mappingConverter' while setting constructor argument; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'mappingConverter': Cannot resolve reference to bean 'mappingContext' while setting constructor argument; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'mappingContext': Invocation of init method failed; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'com.han.mongo.listeners.VisitorMongoEventListener#0': Injection of autowired dependencies failed; nested exception is org.springframework.beans.factory.BeanCreationException: Could not autowire field: private org.springframework.data.mongodb.core.MongoTemplate com.han.mongo.listeners.VisitorMongoEventListener.mongoTemplate; nested exception is org.springframework.beans.factory.BeanCurrentlyInCreationException: Error creating bean with name 'mongoTemplate': Requested bean is currently in creation: Is there an unresolvable circular reference?
	at org.springframework.beans.factory.support.BeanDefinitionValueResolver.resolveReference(BeanDefinitionValueResolver.java:328)
<snip>
Caused by: org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'mappingConverter': Cannot resolve reference to bean 'mappingContext' while setting constructor argument; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'mappingContext': Invocation of init method failed; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'com.han.mongo.listeners.VisitorMongoEventListener#0': Injection of autowired dependencies failed; nested exception is org.springframework.beans.factory.BeanCreationException: Could not autowire field: private org.springframework.data.mongodb.core.MongoTemplate com.han.mongo.listeners.VisitorMongoEventListener.mongoTemplate; nested exception is org.springframework.beans.factory.BeanCurrentlyInCreationException: Error creating bean with name 'mongoTemplate': Requested bean is currently in creation: Is there an unresolvable circular reference?
	at org.springframework.beans.factory.support.BeanDefinitionValueResolver.resolveReference(BeanDefinitionValueResolver.java:328)
<snip>
Caused by: org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'mappingContext': Invocation of init method failed; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'com.han.mongo.listeners.VisitorMongoEventListener#0': Injection of autowired dependencies failed; nested exception is org.springframework.beans.factory.BeanCreationException: Could not autowire field: private org.springframework.data.mongodb.core.MongoTemplate com.han.mongo.listeners.VisitorMongoEventListener.mongoTemplate; nested exception is org.springframework.beans.factory.BeanCurrentlyInCreationException: Error creating bean with name 'mongoTemplate': Requested bean is currently in creation: Is there an unresolvable circular reference?
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1420)
<snip>
Caused by: org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'com.han.mongo.listeners.VisitorMongoEventListener#0': Injection of autowired dependencies failed; nested exception is org.springframework.beans.factory.BeanCreationException: Could not autowire field: private org.springframework.data.mongodb.core.MongoTemplate com.han.mongo.listeners.VisitorMongoEventListener.mongoTemplate; nested exception is org.springframework.beans.factory.BeanCurrentlyInCreationException: Error creating bean with name 'mongoTemplate': Requested bean is currently in creation: Is there an unresolvable circular reference?
	at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor.postProcessPropertyValues(AutowiredAnnotationBeanPostProcessor.java:288)
<snip>
Caused by: org.springframework.beans.factory.BeanCreationException: Could not autowire field: private org.springframework.data.mongodb.core.MongoTemplate com.han.mongo.listeners.VisitorMongoEventListener.mongoTemplate; nested exception is org.springframework.beans.factory.BeanCurrentlyInCreationException: Error creating bean with name 'mongoTemplate': Requested bean is currently in creation: Is there an unresolvable circular reference?
	at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor$AutowiredFieldElement.inject(AutowiredAnnotationBeanPostProcessor.java:508)
<snip>
Caused by: org.springframework.beans.factory.BeanCurrentlyInCreationException: Error creating bean with name 'mongoTemplate': Requested bean is currently in creation: Is there an unresolvable circular reference?
	at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.beforeSingletonCreation(DefaultSingletonBeanRegistry.java:297)
<snip>

[rasch]

That's a coincidence. I encountered the same problem two days ago. I also had to use the ApplicationContextAware workaround.
I try to inject MongoTemplate into an ApplicationListener class.

public class SessionDestroyedListener implements ApplicationListener<SessionDestroyedEvent> {
	@Autowired
	private MongoTemplate mongoTemplate;
}

This will cause a "Error creating bean with name 'mongoTemplate': Requested bean is currently in creation: Is there an unresolvable circular reference?" error.



The weird part is that there is also an ApplicationListener on ContextRefreshEvent and here the autowiring of MongoTemplate works.

@Component
public class Startup implements ApplicationListener<ContextRefreshedEvent> {

	@Autowired
	private MongoTemplate mongoTemplate;
}

I have no idea why one works and the other throws an exception. I hope somebody can shed some light on this issue.

[canal]

Hi,
Appreciate if you could share your implementation of ApplicationContextAware. I am having similar problem.
many thanks
canal

[johannz]

This is from memory, so I don't guarantee that it's correct but it'd be a starting point...

public class VisitorMongoEventListener extends AbstractMongoEventListener<Visitor> implements ApplicationContextAware {
	private ApplicationContext applicationContext;
	private String repositoryName;
	private VisitorRepository visitorRepository = null;


	public void setApplicationContext(ApplicationContext applicationContext) {
		this.applicationContext = applicationContext;
	}

	public void setRepositoryName(String name) {
		this.repositoryName = name;
	}

	public VisitorRepository getVisitorRepository() {
		if (visitorRepository == null) {
			visitorRepository = (VisitorRepository)(applicationContext.getBean(repositoryName));
		}
		return visitorRepository;
	}

@Override
	public void onBeforeConvert(Visitor source) {
		if (StringUtils.isBlank(source.setEmbeddedValue())) {
			String value= getVisitorRepository().lookupSomeOtherValueToEmbed(source);
			source.setEmbeddedValue(value);
		}
	}
}

[canal]

thank you very much!

[Oliver Gierke]

Injection into fields is considered bad practice anyway (how would you unit test that class?). Setter injection should work. The general problem is that you introduce a circular dependency Listener > MongoTemplate > MappingContext > Listener. Would it make sense to implement a custom Converter for your Visitor class instead?