VoK Utilities

This page documents additional VoK utilities available to all VoK projects.

Support for Session

VoK provides a Session object that wraps the current VaadinSession:

Session.current — the current VaadinSession.
Session["key"] = value — store/retrieve values keyed by string.
Session[MyService::class] = MyService() — store a session-scoped service keyed by its class.
Session.getOrPut(MyService::class) { MyService() } — the idiomatic way to lazily attach a session-scoped service.

Session is also the recommended hook point for session-scoped services, so you don’t need a DI container. For example, a user-login module can attach a LoggedInUser service that holds the currently logged-in user and the login/logout logic:

class LoggedInUser : Serializable {
    var user: User? = null
        private set
    val isLoggedIn: Boolean get() = user != null

    fun login(username: String, password: String) {
        val u = User.findByUsername(username) ?: throw LoginException("No such user $username")
        if (!u.validatePassword(password)) throw LoginException("$username: invalid password")
        user = u
    }

    fun logout() {
        user = null
        Session.current.close()
    }
}
val Session.loggedInUser: LoggedInUser get() = getOrPut(LoggedInUser::class) { LoggedInUser() }

Session.loggedInUser.login(...) is now usable from anywhere — no DI needed.

Note: the session is accessible only from code holding the Vaadin UI lock — typically Vaadin-driven request handling. Background threads must capture a UI reference and call ui.access { … } to interact with the session.

Cookies

There is a Cookies singleton for cookie access on the current request/response:

Cookies += Cookie("autologin", "secret") — add a cookie.
Cookies.delete("autologin") — remove a cookie.
Cookies["autologin"] — read a cookie from the current request (returns null if absent).