RuntimeException and GraphQLError in Kotlin and Java

Question

I try to develop a REST API with GraphQL and Kotlin and I'm facing the following problem: I try to create a custom Exception that extends RuntimeException and implements GraphQLError and in Kotlin I can not do this because I'm receiveing this: Accidental override when using third party Java interface and extending RuntimeException in kotlin.

I resolve this problem with an workaround by creating a Java class for my CustomException.

But I don't know why, when I create a kotlin class that extends RuntimeException and implements GraphQLError, I need to override the getMessage() method from GraphQLError, but when I create a java class that extends RuntimeException and implements GraphQLError I don't need to override the getMessage() method from GraphQLError.

Thank you!

I am not into Kotlin, but as I read it, this is a known problem in Kotlin that is not solved yet: KT-24822 (and others) — Arnold Schrijver
Yeah, I understand that problem, but my question was about another fact: why I need to override the getMessage() method in Kotlin, but not in Java. — Dina Bogdan

Kisschr Kisschr · Accepted Answer · 2020-04-24T10:18:31

Annotate message with @JvmField like:

class MyError(@JvmField override val message: String?, private val invalidField: String? = null) : RuntimeException(message), GraphQLError {

    override fun getMessage(): String = super.message ?: "no error message set"

    override fun getLocations(): List<SourceLocation> = emptyList()

    override fun getErrorType(): ErrorType = ErrorType.DataFetchingException

    override fun getExtensions(): Map<String, Any> = if(invalidField!=null)
        Collections.singletonMap<String, Any>("invalidField", invalidField)
    else
        Collections.emptyMap()
}

RuntimeException and GraphQLError in Kotlin and Java

2 Answers