Drop-in reloading of a client on session loss based on calling a local window.serverReload function.

ReloadOnSessionLoss.scala

package bootstrap.liftweb {
  import net.liftweb.common._
  import net.liftweb.http._
    import js._
    import LiftRules._
  import net.liftweb.util.Helpers._

  /**
   * Provides automatic reloading of the client on session loss.
   *
   * Lift keeps tweaking how they do this, but this is our tried-and-true
   * approach for now. It's suggested that we keep monitoring Lift changes to
   * how they do things so that we can adjust if they come up with a better
   * strategy. One key difference is, at last check, Lift redirects the user to
   * a set location (e.g., /) configured in LiftRules, whereas we reload the
   * current page.
   *
   * Call ReloadOnSessionLoss.setup in Boot.scala to install the handlers properly.
   */
  object ReloadOnSessionLoss {
    def dispatch : DispatchPF = {
      case req if firstSeenCometRequest_?(req) => () => Full(responseForFirstCometRequest(req))
    }

    def actorsForCometRequest(req:Req) : Box[List[(LiftCometActor, Long)]] = {
      req.path.wholePath match {
        case prefix :: tail if prefix == LiftRules.cometPath && (tail.length != 2 || tail(1) != LiftRules.cometScriptName()) =>
          Full(
            req.params.toList.flatMap {
              case (name, when) =>
                S.session.open_!.getAsyncComponent(name).toList.map(c => (c, toLong(when)))
            }
          )
        case _ => Empty
      }
    }

    // Returns true if this is the first comet request seen for this client.
    def firstSeenCometRequest_?(req:Req) = {
      (for {
        actors <- actorsForCometRequest(req)
      } yield {
        actors.isEmpty
      }) openOr (
        false
      )
    }

    def responseForFirstCometRequest(req:Req) = {
      JsCommands(List(new JE.JsRaw("lift_toWatch = {}; window.serverReload ? window.serverReload() : window.location.reload();") with JsCmd)).toResponse
    }

    def setup {
      // It's important to do this in order to control our own session loss
      // scenario.
      LiftRules.redirectAjaxOnSessionLoss = false

      LiftRules.dispatch.append(dispatch)
    }
  }
}