getAnnotation for Java annotation used on Kotlin method returns null

Question

Say, I have the following interface:

interface AppRepository : GraphRepository<App> {

    @Query("""MATCH (a:App) RETURN a""")
    fun findAll(): List<App>
}

In a test I want to check specifics of the query string and therefore I do

open class AppRepositoryTest {

    lateinit @Autowired var appRepository: AppRepository

    @Test
    open fun checkQuery() {
        val productionMethod = appRepository.javaClass.getDeclaredMethod("findAll")
        val productionQuery = productionMethod!!.getAnnotation(Query::class.java)

        //demo test
        assertThat(productionQuery!!.value).isNotEmpty() //KotlinNPE
    }
}

For a reason I don't comprehend, productionQuery is nnull. I have double checked that the types of the imported Query in the test class and the Query in the repository are the same.

Thus, why is the productionQuery null in this case?

Answer 1

You're loading annotations on findAll from the implementing class (i.e. the class of the appRepository instance), not on findAll from the interface. To load annotations from AppRepository instead:

val productionMethod = AppRepository::class.java.getDeclaredMethod("findAll")
val productionQuery = productionMethod!!.getAnnotation(Query::class.java)