JUnit, @ControllerAdvice and lack of checked exceptions in Kotlin

Question

I wrote a validation advisor in Kotlin which throws EntityValidationException when validation fails:

@Aspect
@Named
class ValidationAdvisor
@Inject constructor(val validator: EntityValidator) {
    @Around(EVERY_SAVE_AND_UPDATE_TO_DATABASE)
    fun validate(point: ProceedingJoinPoint): Any {
        val result: List<ConstraintViolation<Any>> = validator.validate(getEntity(point))
        if (isEntityValid(result))
            return point.proceed()

        throw EntityValidationException(
            violationInfos = result as List<ConstraintViolationInfo>
        )
    }

    private fun getEntity(point: ProceedingJoinPoint): Any {
        return point.args[0]
    }

    private fun isEntityValid(result: List<ConstraintViolation<Any>>): Boolean {
        return result.isEmpty()
    }

    companion object {
        const val EVERY_SAVE_AND_UPDATE_TO_DATABASE = "execution(* beans.repositories.BaseRepository.save(..))"
    }
}

I have a JUnit test (I write some parts in Kotlin and some in Java, to learn Kotlin in existing private project) which checks if exception is thrown:

@Test(expected = EntityValidationException.class)
public void test_WhenNameIsNotPresent_ThenExceptionIsThrown() throws Exception {
    repository.save(/* entity to save */);
}

But then I saw that test fails because it throws UndeclaredThrowableException instead of EntityValidationException . Next, I read that Kotlin does not have checked exception . I think not only me have this problem - I am pretty sure that way of handling exceptions with @ControllerAdvice in Spring and Java also may be problematic when we decide to switch to Kotlin in production projects - because it rely on class which is thrown, and throwing UndeclaredThrowableException take away from us this possibility. Is there a way to by-pass this behaviour, to make sure that is possible to switch to Kotlin and old Spring way of handling exceptions (and unit tests for ValidationAdvisor ) will remain unchanged? Thank you in advance for any help.

PS Github repo for project is available here: Playgroud for Kotlin, Spring Data etc. .

PS2 Stacktrace:

at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.run(SpringJUnit4ClassRunner.java:191)
    at org.junit.runner.JUnitCore.run(JUnitCore.java:137)
    at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:68)
    at com.intellij.rt.execution.junit.IdeaTestRunner$Repeater.startRunnerWithArgs(IdeaTestRunner.java:51)
    at com.intellij.rt.execution.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:237)
    at com.intellij.rt.execution.junit.JUnitStarter.main(JUnitStarter.java:70)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:497)
    at com.intellij.rt.execution.application.AppMain.main(AppMain.java:147)
Caused by: java.lang.reflect.UndeclaredThrowableException
    at com.sun.proxy.$Proxy65.save(Unknown Source)
    at ActorValidationTest.test_WhenNameIsNotPresent_ThenExceptionIsThrown(ActorValidationTest.java:26)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:497)
    at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:50)
    at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
    at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:47)
    at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
    at org.junit.internal.runners.statements.ExpectException.evaluate(ExpectException.java:19)
    ... 26 more
Caused by: beans.validator.exceptions.EntityValidationException
    at beans.aop.validation.ValidationAdvisor.validate(ValidationAdvisor.kt:23)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:497)
    at org.springframework.aop.aspectj.AbstractAspectJAdvice.invokeAdviceMethodWithGivenArgs(AbstractAspectJAdvice.java:629)
    at org.springframework.aop.aspectj.AbstractAspectJAdvice.invokeAdviceMethod(AbstractAspectJAdvice.java:618)
    at org.springframework.aop.aspectj.AspectJAroundAdvice.invoke(AspectJAroundAdvice.java:70)
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179)
    at org.springframework.aop.interceptor.ExposeInvocationInterceptor.invoke(ExposeInvocationInterceptor.java:92)
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179)
    at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:213)
    ... 37 more

For me looks like EntityValidationException (which I want to be thrown) causes UndeclaredThrowableException . EntityValidationException Kotlin class code:

package beans.validator.exceptions

import beans.validator.constraintViolation.ConstraintViolationInfo

class EntityValidationException (val violationInfos: List<ConstraintViolationInfo>) : Exception() {
}

PS3 This also didn't work:

@Around(EVERY_SAVE_AND_UPDATE_TO_DATABASE)
@Throws(EntityValidationException::class)
fun validate(point: ProceedingJoinPoint): Any /* rest of code*/

PS4 Maybe the problem is that @Aspect is @Around Spring Data repository?

companion object {
        const val EVERY_SAVE_AND_UPDATE_TO_DATABASE = "execution(* beans.repositories.BaseRepository.save(..))"
    }
....
@NoRepositoryBean
public interface BaseRepository<ENTITY, IDENTIFIER extends Serializable>
        extends JpaRepository<ENTITY, IDENTIFIER>, JpaSpecificationExecutor<ENTITY> {
}

Answer 1

You're trying to make the method save() or your repository throw a checked exception that it doesn't declare. So even if the aspect declares it, that can't work. You need to make your exception extend RuntimeException .