VoK Utilities

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

Support for Session

Provides a Session object which gives handy access to the VaadinSession:

Session.current returns the current VaadinSession.
Session["key"] = value allows you to retrieve and/or store values into the session
Session[MySessionScopedService::class] = MySessionScopedService() allows you to store session-scoped services into the session. However, read below on how to do this properly.

Another important role of the Session object is that it provides a default point to which you can attach your session-scoped services. For example, the user login module of your app can attach the LoggedInUser service which contains both the currently logged-in user, and the means to log in and log out:

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

  fun login(username: String, password: String) {
    val user = User.findByUsername(username) ?: throw LoginException("No such user $username")
    if (!user.validatePassword(password)) throw LoginException("$username: invalid password")
    this.user = user
  }
  
  fun logout() {
    user = null
    // http://stackoverflow.com/questions/26404821/how-to-restart-vaadin-session
    Page.getCurrent().setLocation(VaadinServlet.getCurrent().servletConfig.servletContext.contextPath)
    Session.current.close()
  }
}
val Session.loggedInUser: LoggedInUser get() = getOrPut { LoggedInUser() }

By using the above code, you will now be able to access the LoggedInUser from anywhere, simply by calling Session.loggedInUser.login(). No DI necessary!

Note: the session is accessible only from the code being run by Vaadin, with Vaadin UI lock properly held. It will not be accessible for example from background threads - you will need to store the UI reference and call ui.access() from your background thread.

Cookies

There is a Cookies singleton which provides access to cookies attached to the current request:

Use Cookies += Cookie("autologin", "secret") to add a cookie;
Use Cookies.delete("autologin") to remove a cookie.
Use Cookies["autologin"] to access a cookie for the current request.