home | career | drupal | java | mac | mysql | perl | scala | uml | unix  

Lift Framework example source code file (LazyLoad.scala)

This example Lift Framework source code file (LazyLoad.scala) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Java - Lift Framework tags/keywords

asyncrendercomet, asyncrendercomet, box, cometcreationinfo, comment, empty, full, full, jscmd, nodeseq, nodeseq, ready, ready, render

The Lift Framework LazyLoad.scala source code

 * Copyright 2007-2011 WorldWide Conferencing, LLC
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *     http://www.apache.org/licenses/LICENSE-2.0
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * See the License for the specific language governing permissions and
 * limitations under the License.

package net.liftweb
package builtin
package snippet

import xml._
import http._
import common._
import actor._
import util._
import http.js._
import JsCmds._
import JE._
import S._
import Helpers._

object LazyLoad extends DispatchSnippet {
  private object myFuncName extends TransientRequestVar(Helpers.nextFuncName)
  private object myActor extends TransientRequestVar[Box[CometActor]](Empty)

  def dispatch: DispatchIt = {
    case _ => render _

  def render(xhtml: NodeSeq): NodeSeq = {
    (for {
      session <- S.session ?~ ("FIXME: Invalid session")
    } yield {
      // if we haven't created the actor yet, register on this
      // thread to create the AsyncRenderComet actor
      if (myActor.isEmpty) {
          (ccinfo: CometCreationInfo) =>
            ccinfo match {
              case CometCreationInfo(theType @ "AsyncRenderComet",
                                     session) => {
                val ret = new AsyncRenderComet()
                                   name, defaultXml, attributes)
                ret ! PerformSetupComet2(if (ret.sendInitialReq_?) 
       S.request.map(_.snapshot) else Empty)
                // and save it in the request var
              case _ => Empty

      val id = Helpers.nextFuncName

      val func: () => JsCmd = 
        session.buildDeferredFunction(() => Replace(id, xhtml))

      <div id={id}>
        S.attr("template") match {
          case Full(template) => <lift:embed what={template}/>
          case _ => <img src="/images/ajax-loader.gif" alt="Loading"/>
      </div>++ (myActor.is match {
        case Full(actor) => actor ! Ready(func); NodeSeq.Empty
        case _ => session.setupComet("AsyncRenderComet", Full(myFuncName.is), Ready(func))
    }) match {
      case Full(x) => x
      case Empty => Comment("FIX"+ "ME: session or request are invalid")
      case Failure(msg, _, _) => Comment(msg)



private case class Ready(js: () => JsCmd)
private case class Render(js: JsCmd)

 * The Comet Actor for sending down the computed page fragments
class AsyncRenderComet extends CometActor {

  override def lifespan: Box[TimeSpan] = Full(90 seconds)

  def render = NodeSeq.Empty

  // make this method visible so that we can initialize the actor
  override def initCometActor(theSession: LiftSession,
                               theType: Box[String],
                               name: Box[String],
                               defaultXml: NodeSeq,
                               attributes: Map[String, String]) {
    super.initCometActor(theSession, theType, name, defaultXml,

  override def lowPriority : PartialFunction[Any, Unit] = {
    // farm the request off to another thread
    case Ready(js) => 
      Schedule.schedule(() => this ! Render(js()), 0 seconds)

    // render it
    case Render(js) => 

Other Lift Framework examples (source code examples)

Here is a short list of links related to this Lift Framework LazyLoad.scala source code file:

my book on functional programming


new blog posts


Copyright 1998-2019 Alvin Alexander, alvinalexander.com
All Rights Reserved.

A percentage of advertising revenue from
pages under the /java/jwarehouse URI on this website is
paid back to open source projects.