CSC/ECE 517 Fall 2014/ch1a 4 wl

WEB DEVELOPMENT USING LIFT

Lift Web Framework

Components

1. LiftCore: This is the web processor of the framework which handles the following functions.
   1. Request/Response
   2. Rendering Pipeline
   3. Invoking User Functions
2. LiftRules : Lift Configuration
3. LiftSession: Inherent Session State.
4. S: stateful context for request/response lifecycle.
5. SiteMap: contains web pages for the lift application.
6. SHtml: helper functions for XHtml.
7. Views: Views as XML content. Allows composing views from not only html files but other contexts too.
8. LiftResponse: Abstraction of response sent to the client.
9. Comet: allows sending asynchronous content to browser.
10. ORM: A specialized library.
11. HTTP Auth: provides control over authentication model.
12. JS API: JavaScript abstraction layer.

Getting Started

Set Up on Eclipse

1. Download “Scala IDE for Eclipse” : http://scala-ide.org/
2. Install plugin in Eclipse from this update site : http://download.scala-ide.org/sdk/helium/e38/scala211/stable/site
3. Once the plugin is installed restart Eclipse
4. Install sbteclipse by adding the following to projects/plugins.sbt in your Lift Project: addSbtPlugin("com.typesafe.sbteclipse" % "sbteclipse-plugin" % "2.5.0")
5. You can then create Eclipse project files (.project and .classpath) by entering the following into the SBT prompt: eclipse

Basic Web Application Structure

Step 1: Making a SiteMap entry

Every page on the site needs a SiteMap entry.

def sitemap(): SiteMap = SiteMap(
  Menu("Home") / "index",
  Menu("Second Page") / "second"
)

Step 2: Creating the view

Create an HTML file that corresponds to the sitemap entry.

<meta content="text/html; charset=UTF-8" http-equiv="content-type">
    <title>Home</title>
   
   
    <div id="main" class="lift:surround?with=default&at=content">
      <div>
        Hi, I'm a page that contains the time:
        <span class="lift:TimeNow">??? some time</span>.
      </div>

      <div>
        And a button: <button class="lift:ClickMe">Click Me</button>.
      </div>
    </div>

Step 3 : Creating the Snippet

A snippet can be thought of as a controller which has rules for transforming the section of your template.

package code
package snippet

import net.liftweb._
import util._
import Helpers._

object TimeNow {
  def render = "* *" #> now.toString
}

Advantages

1. Built on Scala which is a powerful functional language.
2. Multiple Component support : Divides the controls into snippets which can be used together on a single page thereby not coupling a page with a controller.
3. CSS Binding : allows to navigate the HTML Dom tree.
4. Native Javascript/Ajax Support
5. Out-of-box Security.
6. Lazy Loading & Parallel Page rendering : Lift shows automatic spinners on area still being loaded, components are able to load over multiple thread at the same time.

Disadvantages

1. Lots of state kept in session.
2. Learning Curve as no more MVC.

References

1. http://exploring.liftweb.net/master/index-9.html
2. http://blog.fliptop.com/blog/2013/03/10/why-lift-webframework-is-my-favorite/
3. http://www.quora.com/What-are-the-advantages-and-disadvantages-of-writing-a-web-application-in-Scala-using-Lift