Prohibit circular references by default

[wilkinsona]

We believe that circular references between beans should be avoided if at all possible. To help users avoid accidentally creating such dependency cycles, we should configure the BeanFactory to prohibit circular references by default. We'll allow them to be enabled via API and configuration property for those that really need them, as we did with bean definition overriding in 2.1. We should also update ApplicationContextRunner at the same time.

[bmaehr]

@wilkinsona I'm missing a good solution for the self references (needed für transaction handling) which are detected now.

[wilkinsona]

If you'd like some help, please ask on Stack Overflow or Gitter. Someone trying to help you will need to see the code that contains the circular references so that they can advise you on how to remove them.

[bmaehr]

@wilkinsona That's not true. It is a common pattern to inject the bean itself to be able to use spring annotations for "internal" calls. So if this behavior is disabled by default there should be a general suggestion how to solve these kind of problems (without the need changing the structure of the beans which are designed that way because of a good reason).

spring-projects/spring-framework#13096
https://stackguides.com/questions/3037006/starting-new-transaction-in-spring-bean
https://www.geekyhacker.com/2020/04/02/how-to-use-spring-boot-cacheable-on-self-invocation/

So I'm not looking for solution in a special case, there should be a feasible general solution for these use cases.

[bennettdams]

I would also like to know of a recommended solution.

Here is another very common use case: I have repo and a custom repo, where the custom repo uses the repo inside. Right now, the only thing that I came up with to prevent the circular reference problem is by using @Lazy for the initialization:

interface DogRepo : DogRepoCustom, MongoRepository<Dog, String> { ... }

class DogRepoImpl(@Lazy private val dogRepo: DogRepo) : DogRepoCustom { ... }

interface DogRepoCustom { ... }

The problem is that using @Lazy here is considered a workaround by someone who knows this topic way better than me.

[wilkinsona]

If you are looking for a general solution that does not require you to change your code, you can use the configuration property to permit circular dependencies again. This property is described in the release notes for Spring Boot 2.6.

[bennettdams]

@wilkinsona Thanks! I think the Spring team had good reasons to prohibit circular dependencies and I want to follow that.
I'm totally down to change my code, but I don't know the best way to do that. Taking my example above (repo & custom repo), is using @Lazy a bad idea? If yes, what is the recommended way to do so?
I think Spring should add something to the docs to show some examples on what to do against circular dependencies, now that you state that having them is a bad idea. I would like to know this for my example obviously, but the topic in general could be explained in the docs.