Flash Map with request Support

gistfile1.scala

trait MyFlashMapSupport extends Handler {
  this: CoreDsl with DynamicScope with SessionSupport =>

  import FlashMapSupport._

  abstract override def handle(req: HttpServletRequest, res: HttpServletResponse) {
    withRequest(req) {
      val f = getFlash(req)
      val isOutermost = !req.contains(lockKey)
      if (isOutermost) {
        req(lockKey) = "locked"
        if (sweepUnusedFlashEntries(req)) {
          f.flag()
        }
      }
      super.handle(req, res)
      /*
       * http://github.com/scalatra/scalatra/issues/41
       * http://github.com/scalatra/scalatra/issues/57
       *
       * Only the outermost FlashMapSupport sweeps it at the end.
       * This deals with both nested filters and redirects to other servlets.
       */
      if (isOutermost) {
        f.sweep()
      }

      flashMapSetSession(f)
    }
  }

  /**
   * Override to implement custom session retriever, or sanity checks if session is still active
   * @param f
   */
  def flashMapSetSession(f: FlashMap) {
    try {
      // Save flashMap to Session after (a session could stop existing during a request, so catch exception)
      session(sessionKey) = f
    } catch {
      case e: Exception =>
    }
  }

  /**
   * Try's to receive a flashMap from current request, if it fails:
   * - Try to receive map from Session orElse create a new map
   * - Save this flashMap to request to maintain state
   *
   * @param req current request
   * @return flashMap
   */
  private def getFlash(req: HttpServletRequest): FlashMap = {
    req.get(sessionKey).map(_.asInstanceOf[FlashMap]).getOrElse {
      val map = session.get(sessionKey).map {
        _.asInstanceOf[FlashMap]
      }.getOrElse(new FlashMap)

      req.setAttribute(sessionKey, map)
      map
    }

  }


  /**
   * Returns the [[org.scalatra.FlashMap]] instance for the current request.
   */
  def flash = getFlash(request)

  /**
   * Determines whether unused flash entries should be swept.  The default is false.
   */
  protected def sweepUnusedFlashEntries(req: HttpServletRequest) = false
}