Starting from Spring-Boot 3.2.x the @SpyBean is not able to initialise MongoRepository bean of the generic type.

[pavlo-reshetniak]

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

1. Make sure the spring-boot-starter-parent has version 3.2.x (e.g. 3.2.4) in the parent POM file
2. 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;

[wilkinsona]

The change in behavior is due to spring-projects/spring-data-commons@98f20a4. 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:

spring-boot/spring-boot-project/spring-boot-test/src/main/java/org/springframework/boot/test/mock/mockito/MockitoPostProcessor.java

Lines 258 to 261 in a3d62e0

	Object attribute = beanDefinition.getAttribute(FactoryBean.OBJECT_TYPE_ATTRIBUTE);
	if (resolvableType.equals(attribute) || type.equals(attribute)) {
	beans.add(beanName);
	}

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:

spring-boot/spring-boot-project/spring-boot-test/src/main/java/org/springframework/boot/test/mock/mockito/MockitoPostProcessor.java

Lines 252 to 253 in a3d62e0

	Set<String> beans = new LinkedHashSet<>(
	Arrays.asList(beanFactory.getBeanNamesForType(resolvableType, true, false)));

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().

[wilkinsona]

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

[quaff]

FYI, there are some improvements about repository definition's target type:
spring-projects/spring-data-commons@dd081d4 spring-projects/spring-data-commons@88011e6

Not sure Boot could benefit from it.

[quaff]

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

}

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

[wilkinsona]

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