If a spring singleton bean has a dependency to another bean, will they be destroyed in the reverse order they were created in?

Question

This is a question about the default behavior of Spring. Say I have a singleton bean called BeanA, which has a constructor dependency to a singleton bean called BeanB. BeanB will have to be created before BeanA in order to satisfy that dependency. If both beans implement the DisposableBean interface I would expect the destroy method to be called in the reverse order that the beans were created in, but I can't see it mentioned in the documentation. The best I've found is the documentation for the DependsOn annotation (https://docs.spring.io/spring-framework/docs/current/javadoc-api/org/springframework/context/annotation/DependsOn.html) but it doesn't mention what the behavior is when DependsOn isn't used.

Edit: As I mentioned in a comment below: I've tried this out and in my test it works as expected. BeanA is destroyed before BeanB. I would like some documentation or similar to know that this is always the case though.

user_1083108 · Answer

After testing and looking through the Spring source code (for example the DefaultSingletonBeanRegistry mentioned by M. Deinum in a comment) I have found that two singleton beans where one is dependendent on the other will indeed be destroyed in the reverse order they are created in. When thinking about it I have a hard time seeing how it could work in another way. If the beans were not destroyed in the reverse order it would cause a lot of problems. For example, during the shutdown of an app a bean could try to use another bean that has already been destroyed. Unfortunately, I still haven't found any confirmation of the behavior in the documentation.

If a spring singleton bean has a dependency to another bean, will they be destroyed in the reverse order they were created in?

1 Answers