DuplicateKey.kt

class CustomErrorWebExceptionHandler : AbstractErrorWebExceptionHandler() {

    // Define constructor here

    override  fun getRoutingFunction(errorAttributes: ErrorAttributes): RouterFunction<ServerResponse> {

        return RouterFunctions
                .route<ServerResponse>(aPredicate, aHandler)
//                .andRoute(anotherPredicate, anotherHandler)
                .filter { request, next ->
                    try {
                        next.handle(request)
                    } catch (ex: Exception) {
                        when (ex) {
                            is ChangeSetPersister.NotFoundException -> ServerResponse.notFound().build()
                            else -> ServerResponse.status(HttpStatus.INTERNAL_SERVER_ERROR).build()
                        }
                    }
                }
    }

}