I have an optional dependency to listener beans in one of my beans. That means that I could have any number of listeners in my Application context.
I have tried to annotate my bean the following way:
@Autowired(required = false)
@Lazy
private List<Listener> listeners = new ArrayList<>(0);
IMO it is intuitive that Spring will
Search for Listener beans only when accessed
Do not crash if no Listener bean is defined in the context, namely return an empty list
I don't know if this is a bug in 4.3.5 or is it just how Spring is designed, but the above code, when no Listener bean is defined, crashes instead of returning an empty list when I try to access the listeners object.
If I use eager initialization, Autowired's required=false injects an empty list. I expected similar behaviour for lazy lists.
This ticket is:
MINOR because I can workaround this issue by using eager initialization, for the mometn
IMPROVEMENT because I have found no documentation on whether it is a design choice or an implementation issue
My container bean's afterPropertiesSet does
log.info("I have {} listeners attached", listeners.size());
Instead of logging 0, the application crashes with the following stack trace
Caused by: org.springframework.beans.factory.NoSuchBeanDefinitionException: No qualifying bean of type 'java.util.List<Manager$Listener>' available: Optional dependency not present for lazy injection point
at org.springframework.context.annotation.ContextAnnotationAutowireCandidateResolver$1.getTarget(ContextAnnotationAutowireCandidateResolver.java:85)
at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:192)
at com.sun.proxy.$Proxy172.size(Unknown Source)
at com.acme.ManagerImpl.afterPropertiesSet(ManagerImpl.java:75)
Before submitting a test case, I'd first like to be clarified what is the expected Spring's behaviour in such situation
In addition to its role for component initialization, this annotation may also be placed on injection points marked with Autowired or Inject: In that context, it leads to the creation of a lazy-resolution proxy for all affected dependencies, as an alternative to using ObjectFactory or Provider.
Affects: 4.3.5
Issue Links:
#20384 Autowire contract is not honored in cases where FactoryBean or @Bean return null
Antonio Anzivino opened SPR-15858 and commented
Hi,
I have an optional dependency to listener beans in one of my beans. That means that I could have any number of listeners in my Application context.
I have tried to annotate my bean the following way:
IMO it is intuitive that Spring will
I don't know if this is a bug in 4.3.5 or is it just how Spring is designed, but the above code, when no Listener bean is defined, crashes instead of returning an empty list when I try to access the listeners object.
If I use eager initialization, Autowired's required=false injects an empty list. I expected similar behaviour for lazy lists.
This ticket is:
My container bean's afterPropertiesSet does
Instead of logging 0, the application crashes with the following stack trace
Before submitting a test case, I'd first like to be clarified what is the expected Spring's behaviour in such situation
I have reviewed Spring docs on Lazy. The javadoc does not cite the case of optional Collection-dependencies
https://docs.spring.io/spring/docs/current/javadoc-api/org/springframework/context/annotation/Lazy.html
Affects: 4.3.5
Issue Links:
@Bean
return nullReferenced from: commits ec1eafc, 80bf394
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