Exception Handling
When the backend code throws an unhandled exception, it will be logged on the server side and then propagated by KVision to the frontend side. There are of course many different classes of exceptions on the JVM and it's not possible to transform those types directly to the JS side. So only the exception message is propagated and the generic
Exception
object is created on the frontend side. There is a special
io.kvision.remote.ServiceException
class defined in common KVision code. Unlike all other exception classes this one will be propagated directly from ServiceException
to ServiceException
and will not be logged on the backend side. It should be used as typical business error indication.Backend.kt
@Suppress("ACTUAL_WITHOUT_EXPECT")
actual class PasswordService : IPasswordService {
override suspend fun changePassword(oldPassword: String, newPassword: String) {
if (oldPassword == newPassword) {
throw ServiceException("You should really change your password")
}
// ...
}
}
Frontend.kt
val passwordService = PasswordService()
try {
passwordService.changePassword(oldPassword, newPassword)
} catch (e: ServiceException) {
Alert.show("Error", e.message)
}
Since KVision 5.8.2 it is possible to define custom exception types in the common module, that will be propagated from the backend to the fronted side. Such exceptions need to inherit from
AbstractServiceException
and need to be annotated with @KVServiceException
annotation.@KVServiceException
class MyFirstException(override val message: String) : AbstractServiceException()
@KVServiceException
class MySecondException(override val message: String) : AbstractServiceException()
Such exceptions are automatically registered by the framework and you should be able to throw custom exceptions on the backend side and catch them on the frontend side.
When returning
Result<T>
from the remote methods, the exceptions wrapped in the Result
class are serialized and deserialized the same way as when being thrown. So you can safely use ServiceException
and other user-defined exceptions when working with Result<T>
on both the frontend and the backend side of your application.Last modified 3mo ago