How to add inner classes to Spring application context for Unit Testing?

Question

I have a bean whose business logic loads beans of a certain type from the ApplicationContext in order to process them.

For my jUnit tests, I would like to create some dummy beans within my unit test class and see if my bean under test properly processes them. However, I am not sure what the best way to accomplish this is.

If I just declare my inner class within my test class, Spring will not have it as part of its application context. I realize that I could inject my application context within my jUnit class, and then use appContext.registerPrototype() to add it, however, I thought there might be a cleaner way using annotations.

I've tried to annotate the internal class with @Component, but not surprisingly, it did not work.

public class PatchEngineTest extends TestBase {
    @Component
    protected class Patch1 extends PatchBaseImpl implements Patch{
        public void applyPatch() throws Exception {
            // does nothing
        }
    }


    @Autowired PatchRepository patchRepository;
    @Autowired Patch1 patch1;

    @Test
    public void test() {
        fail("Not yet implemented");
    }

}

Not surprisingly, I get the following error message:

Caused by: org.springframework.beans.factory.NoSuchBeanDefinitionException: No qualifying bean of type [com.ia.patch.PatchEngineTest$Patch1] found for dependency: expected at least 1 bean which qualifies as autowire candidate for this dependency. Dependency annotations: {@org.springframework.beans.factory.annotation.Autowired(required=true)}

Is there any way of doing this?

My question is: why are you trying so hard to have all these inner classes? — Sotirios Delimanolis, Oct 18 '13 at 02:45
@SotiriosDelimanolis They are tiny inner classes specific only to the unit test in question, so just want to keep the code together. — Eric B., Oct 18 '13 at 03:13

score 14 · Accepted Answer · answered Oct 18 '13 at 02:26

14

You need to make your inner class static; Spring can't instantiate a non-static inner class as a bean. If there really is a valid reason why it needs to be non-static, you could create it manually in an @Bean method.

answered Oct 18 '13 at 02:26

chrylis -cautiouslyoptimistic-

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From my understanding the `@Bean` method would need to be in a JavaConfig class - correct? Or is there somewhat I can include the `@Bean` method within my Test class? – Eric B. Oct 18 '13 at 02:33
Yes, `@Bean`s need to be inside `@Configuration` classes. – chrylis -cautiouslyoptimistic- Oct 18 '13 at 04:24
Thanks, but can my @Configuration JavaConfig be an inner class as well? – Eric B. Oct 18 '13 at 14:32
@EricB. Haven't tried that, but it *should* work. Still has to be a `static` class, though! – chrylis -cautiouslyoptimistic- Oct 18 '13 at 21:29
1

At Spring Boot project v2.0.0.RELEASE Spring is instantiating a non-static inner class, as long as it is public and has @Component annotation. – valijon Apr 01 '18 at 18:47
@chrylis-cautiouslyoptimistic- Can you please explain why 'Spring can't instantiate a non-static inner class as a bean'?? Want to understand the core logic – Rakz Feb 11 '21 at 06:02

score 1 · Answer 2 · answered May 05 '19 at 15:03

1

I also met this problem, and below is my solution :

@RunWith(SpringRunner.class)
@SpringBootTest
@ComponentScan
@ImportAutoConfiguration
public class FooTest {

    @Component
    public static class Bar {

    }
}

I used spring boot 2.1.4.RELEASE

answered May 05 '19 at 15:03

zhuguowei

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How to add inner classes to Spring application context for Unit Testing?

2 Answers2