enum.kt

enum class Provider(val service: String) {
    KAKAO("kakao"),
    APPLE("apple")
}

@RestController
class TestController {
  
  @PostMapping("/test")
  fun testFunc(
    @RequestParam provider: Provider,
    @RequestParam(required = false) oauth_access_token: String?,
    @RequestParam(required = false) authorization_code: String?
  ) {
    val isSupportService: Boolean = when (provider) {
      KAKAO -> oauth_access_token != null
      APPLE -> authorization_code != null
    }
    if (!isSupportService) throw NotSupportedException()
  }
}

if (when (provider) {
    KAKAO -> oauth_access_token == null
    APPLE -> authorization_code == null
}) throw NotSupportedException()

정도로 타협..