Issue

Starting from Spring-Boot 3.2.x the @SpyBean is not able to initialize MongoRepository bean of the generic type. Please check the example project: https://github.com/pavlo-reshetniak/spybean-issue-example

How to reproduce

Make sure the spring-boot-starter-parent has version 3.2.x (e.g. 3.2.4) in the parent POM file
Run unit test: com.example.service.ExampleServiceTest#shouldExtractDataFromMongo

Result

Caused by: org.springframework.beans.BeanInstantiationException: Failed to instantiate [com.example.repository.ExampleRepository]: Specified class is an interface
    at org.springframework.beans.factory.support.SimpleInstantiationStrategy.instantiate(SimpleInstantiationStrategy.java:77)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.instantiateBean(AbstractAutowireCapableBeanFactory.java:1311)
    ... 39 more

Possible workaround

Downgrading the spring-boot-starter-parent to version 3.1.10 will fix the issue
Removing the generic type under the @SpyBean initialization will fix the issue:

From this:

   @SpyBean
   private ExampleRepository<ExampleData> exampleRepository;

to this:

   @SpyBean
   private ExampleRepository exampleRepository;

Comment From: wilkinsona

The change in behavior is due to https://github.com/spring-projects/spring-data-commons/commit/98f20a4457ace08348a8e568eaed2c451e127699. The move away from the FactoryBean.OBJECT_TYPE_ATTRIBUTE to setting the definition's target type means that MockitoPostProcessor now fails to match the generic signature of the spied field:

https://github.com/spring-projects/spring-boot/blob/a3d62e0b2fef26f7fb06781b6a3bf1b5f7b48a07/spring-boot-project/spring-boot-test/src/main/java/org/springframework/boot/test/mock/mockito/MockitoPostProcessor.java#L258-L261

This failed matching means that we don't find the existing bean and instantiating one fails as it's an interface.

It's unfortunate that Framework doesn't find the factory bean when we ask for beans of a particular type:

It doesn't find them as we are not permitting eager init so it only checks raw factory beans and not the beans created by those factory beans. Perhaps this could be improved when the bean definition has additional type information as it does in this case?

In the absence of a change in Framework, when the object type attribute's is null, I think we need to fall back to the target type information that I think we can access through getResolvableType().

Comment From: wilkinsona

I've opened https://github.com/spring-projects/spring-framework/issues/32649 to track a change on the Framework side that will hopefully get this working without changing anything in Boot.

Comment From: quaff

FYI, there are some improvements about repository definition's target type: https://github.com/spring-projects/spring-data-commons/commit/dd081d461435c292db356f976041ca01a94515a2 https://github.com/spring-projects/spring-data-commons/commit/88011e6003e95bba721bb5680b049db0f9c9eaed

Not sure Boot could benefit from it.

Comment From: quaff

public interface ExampleRepository<T extends AbstractData> extends MongoRepository<ExampleData, String> {

}

I don't understand why ExampleRepository is generic? @pavlo-reshetniak

Comment From: wilkinsona

We may get something in Framework 6.2 that helps with this. Until then, we'll have to refine our own matching.

SpringBoot Starting from 3.2.x, @SpyBean is not able to initialise MongoRepository bean of the generic type

Issue

How to reproduce

Result

Possible workaround