All Superinterfaces:

Function<UserIdentityContext,Optional<String>>, Serializable, SerializableFunction<UserIdentityContext,Optional<String>>

Provides a custom identifier of end-users that, if configured, is used the by Vaadin's license server to count unique daily users for a given subscription.

!Important note: Vaadin doesn't collect, neither it stores or anyhow analyses the possible personal information returned by this function. The returned string value is hashed with subscription key as a salt and only then handled further.

Returns non-empty string, wrapped into an Optional, if the identity can be given, e.g. when user is logged in, otherwise returns an empty Optional if no user information is available. The function MUST never return null.

Since:

24.5