Web Application Frameworks - Lecture 05 - Web Information Systems (4011474FNR)

2 December 2005
Web Information Systems
Web Application Frameworks
Prof. Beat Signer
Department of Computer Science
Vrije Universiteit Brussel
http://www.beatsigner.com

October 24, 2014 Beat Signer - Department of Computer Science - bsigner@vub.ac.be 2
Web Application Frameworks
 There exist dozens of web application frameworks!
A web application framework is a software framework that
is designed to support the development of dynamic web-sites,
web applications, web services and web resources.
The framework aims to alleviate the overhead associated
with common activities performed in web development.
For example, many frameworks provide libraries for
database access, templating frameworks and session
management, and they often promote code reuse.
[http://en.wikipedia.org/wiki/Web_application_framework]

Web Application Frameworks ...
 A web application framework offers libraries and
tools to deal with web application issues
 template libraries, session management, database access
libraries etc.
 Some frameworks also offer an abstraction from the
underlying enabling technologies
 e.g. automatic creation of Java Servlets
 Many frameworks follow the Model-View-Controller
(MVC) design pattern
 no mix of application logic and view (e.g. not like in JSP)
 increases modularity and reusability
 Lead to a faster and more robust development process

Model-View-Controller (MVC)
 Model
 data (state) and business logic
 multiple views can be defined for a single model
 when the state of a model changes, its views are notified
 View
 renders the data of the model
 notifies the controller about changes
 Controller
 processes interactions with the view
 transforms view interactions into
operations on the model (state
modification)
Model
Controller
View
notifies
modifies
state
selects view
notifies
gets
state

Apache Struts 2
 Free open source framework for creating enterprise-ready
Java-based web applications
 Action-based MVC Model 2 (Pull MVC) framework
combining Java Servlets and JSP technology
 model
- action (basic building blocks) from which the view can pull information via the
ValueStack
- action represented by POJO (Plain Old Java Object) following the JavaBean
paradigm and optional helper classes
 view
- template-based approach often based on JavaServer Pages (JSP) in
combination with tag libraries (collection of custom tags)
 controller
- based on Java Servlet filter in combination with interceptors

MVC Model 2 (MVC 2) in Struts 2
Model
POJOs
Database
Controller
Servlet
View
e.g. JSP
Browser
1
2
3
4
5
6

Apache Struts 2 Architecture
 Servlet request
 standard filter chain
- interception of requests and
responses
- reusable modular units
- e.g. XSLT transformation
 StrutsPrepareAndExecute
Filter consults controller
(ActionMapper)
 ActionProxy is called if
action has to be executed
 consult Configuration-
Manager
 create ActionInvocation
[http://struts.apache.org/2.1.6/docs/big-picture.html]

Apache Struts 2 Architecture ...
 invoke any interceptors
(controller) before Action
 Action class updates the
model
 ActionInvocation does
a lookup for the Result
 based on Action result code
 mappings in struts.xml
 Result execution (view)
 often based on JSP template
 interceptors in reverse order
 Send response
 again through filter chain
[http://struts.apache.org/2.1.6/docs/big-picture.html]

Apache Struts 2
 ValueStack
 temporary objects, Action objects, ...
 access from JSP via Object Graph Navigational Language (OGNL)
 Multiple view alternatives
 JSP, XSLT, Velocity, ...
 Simplifies web development
 convention over configuration
 intelligent default values reduce the size of configuration files
 fosters modularity and loose coupling (dependency injection)
 standard development process for Struts 2 web applications
 Requires no changes to the servlet container
 regular servlet application

Apache Struts 2 web.xml
<web-app id="WebApp1" version="2.4" xmlns="http://java.sun.com/xml/ns/j2ee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee
http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd">
<filter>
<filter-name>struts</filter-name>
<filter-class>org.apache.struts2.dispatcher.ng.filter.StrutsPrepareAndExecuteFilter
</filter-class>
<init-param>
<param-name>actionPackages</param-name>
<param-value>be.ac.vub.wise</param-value>
</init-param>
</filter>
<filter-mapping>
<filter-name>struts</filter-name>
<url-pattern>/*</url-pattern>
</filter-mapping>
<taglib>
<taglib-uri>/WEB-INF/struts-bean.tld</taglib-uri>
<taglib-location>/WEB-INF/struts-bean.tld</taglib-location>
</taglib>
...
</web-app>

Tag Libraries
 Introduced to encapsulate reusable Java objects in JSP
 provide access to methods on objects
 Apache Struts 2 offers four different libraries
 HTML
- e.g. buttons, form fields, ...
 Template
- tags that are useful for creating dynamic JSP templates
 Bean
- e.g. definitions, parameters, ...
 Logic
- e.g. comparisons, ...

Apache Struts 2 Hello World Example
<%@ taglib prefix="s" uri="/struts-tags" %>
<html>
<head>
<title>Hello World</title>
</head>
<body>
<h1><s:property value="message"/></h1>
<p>Time: <b><s:property value="currentTime" /></b></p>
</body>
</html>
HelloWorld.jsp

Apache Struts 2 Hello World Example ...
package be.ac.vub.wise;
import com.opensymphony.xwork2.ActionSupport;
import java.util.Date;
public class HelloWorldImpl extends ActionSupport {
public static final String MESSAGE = "Hello World!";
public static final String SUCCESS = "success";
private String message;
public String execute() throws Exception {
setMessage(MESSAGE);
return SUCCESS;
}
public void setMessage(String message){
this.message = message;
}
public String getMessage() {
return message;
}
public String getCurrentTime(){
return new Date().toString();
}
} HelloWorldImpl.java

Apache Struts 2 Hello World Example ...
 Execute the Hello World example by sending request to
 http://localhost:8080/wise/HelloWorld.action
<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE struts PUBLIC "-//Apache Software Foundation//DTD Struts Configuration 2.0//EN"
"http://struts.apache.org/dtds/struts-2.0.dtd">
<struts>
<constant name="struts.enable.DynamicMethodInvocation" value="false"/>
<constant name="struts.devMode" value="true"/>
<package name="be.ac.vub.wise" namespace="/wise" extends="struts-default">
<action name="HelloWorld" class="be.ac.vub.wise.HelloWorldImpl">
<result>/pages/HelloWorld.jsp</result>
</action>
...
</package>
...
</struts>
struts.xml

Spring Framework
 Java application framework
 Various extensions for web applications
 Modules
 model-view-controller
 data access
 inversion of control container
 convention-over-configuration
 remote access framework
 transaction management
 authentication and authorisation
 …

Apache Flex
 Software development kit for cross-platform
Rich Internet Applications (RIAs) based on Adobe Flash
 Main components
 Adobe Flash Player runtime environment
 Flex SDK (free)
- compiler and debugger, the Flex framework and user interface components
 Adobe Flash Builder (commercial)
- Eclipse plug-in with MXML compiler and debugger
 Separation of user interface and data
 user interface described in MXML markup language in
combination with ActionScript
- compiled into flash executable (SWF flash movie)

Apache Flex ...
 Flex framework offers various actions
 e.g. HTTPRequest component
 Flex applications can also be deployed as desktop
applications via Adobe AIR (Adobe Integrated Runtime)
<?xml version="1.0" encoding="UTF-8" ?>
<mx:Application xmlns:mx="http://www.adobe.com/2006/mxml" layout="horizontal">
<mx:Script>
<![CDATA[
import mx.controls.Alert;
private function sayHello():void {
Alert.show("Hello " + user.text);
}
]]>
</mx:Script>
<mx:Label fontSize="12" text="Name: " />
<mx:TextInput id="user" />
<mx:Button label="Go" click="sayHello()" />
</mx:Application>
HelloWorld.mxml

Microsoft Silverlight
 Microsoft's platform for Rich Internet Applications
 competitor to Adobe Flash
 Runtime requires a browser plug-in
 Internet Explorer, Firefox, Safari and Google Chrome
 Silverlight Core Common Language Runtime (CoreCLR)
 A Silverlight application consists of
 CreateSilverlight.js and Silverlight.js
- initialise the browser plug-in
 user interface described in the Extensible Application Markup
Language (XAML)
- XAML files are not compiled  indexable by search engines
 code-behind file containing the program logic

Microsoft Silverlight ...
 Programming based on a subset of the .NET Framework
 Silverlight introduces a set of features including
 LocalConnection API
- asynchronous messaging between multiple applications on the same machine
 out-of-browser experiences
- locally installed application that runs out-of-the-browser (OOB apps)
- cross-platform with Windows/Mac
 microphone and Web cam support
 Two types of Silverlight web requests
 WebClient class
- OpenReadAsync (for streaming), DownloadStringAsync as well as uploads
 WebRequest
- register an asynchronous callback handler (based on HttpWebRequest)

OpenLaszlo
 Open source RIA platform
 Two main components
 LZX programming language
- XML and JavaScript
- similar to MXML and XAML
 OpenLaszlo Server
 The Open Laszlo Server compiles LZX applications into
different possible runtime components
 Java Servlets
 binary SWF files
 DHTML (HTML, DOM, JavaScript and CSS)

Ruby on Rails (RoR)
 Open source web application framework
 Combination of
 dynamic, reflective, object-oriented programming language Ruby
- combination of Perl-inspired syntax with "Smalltalk features"
 web application framework Rails
 Based on MVC architectural pattern
 structure of a webpage separated from its functionality via the
unobtrusive JavaScript technique
 The scaffolding feature offered by Rails can
automatically generate some of the models and views
that are required for a website
 developer has to run an external command to generate the code

Ruby on Rails (RoR) ...
 Ruby on Rails Philosophy
 Don't Repeat Yourself (DRY)
- information should not be stored redundantly (e.g. do not store information in
configuration files if the data can be automatically derived by the system)
 Convention over Configuration (CoC)
- programmer only has to specify unconventional application settings
- naming conventions to automatically map classes to database tables (e.g. by
default a 'Sale' model class is mapped to the 'sales' database table)

Video: Ruby on Rails
http://media.rubyonrails.org/video/rails_blog_2.mov

Yii Framework
 PHP framework for the development of Web 2.0
applications that offers a rich set of features
 AJAX-enabled widgets
 web service integration
 authentication and authorisation
 flexible presentation via skins and themes
 Data Access Objects (DAO) interface to transparently access
different database management systems
 integration with the jQuery JavaScript library
 layered caching
 ...

Zend
 Open source PHP framework offering various features
 MVC architectural pattern
 loosely coupled components
 object orientation
 flexible caching
 Simple Cloud API
 features to deal with emails (POP3, IMAP4, …)
 …

CakePHP
 Open source PHP web application framework
 rapid prototyping via scaffolding
 authentication
 localisation
 session management
 caching
 validation
 …

Node.js
 Server-side JavaScript
 handling post/get requests, database, sessions, …
 Write your entire app in one language
 Built-in web server (no need for Apache, Tomcat, etc.)
 High modularity
 plug-ins can be added for desired server-side functionality
 Other more powerful frameworks such as Express.js
build on top of Node.js

Django
 Open source Python web application framework
 don't repeat yourself (DRY)
 object-relational mapper
- mapping between model (Python classes) and a relational database
 integrated lightweight web server
 localisation
 caching
 ...

Web Content Management Systems
 Content management systems that focus on web content
 Main functionality
 data storage and publishing, user management (including access
rights), versioning, workflows
 Offline (create static webpages), online (create
webpages on the fly) and hybrid systems
 Often some kind of server-side caching
 Suited for non-technical users since the underlying
technology is normally completely hidden
 Web CMS Examples
 Joomla, Drupal, ...

Exercise 5
 Web Application Frameworks
 implementation of a Struts 2 application

References
 Struts 2 Quick Guide
 http://www.tutorialspoint.com/struts_2/struts_quick_g
uide.htm
 Apache Struts 2
 http://struts.apache.org/2.x/
 Ian Roughley, Struts 2
 http://refcardz.dzone.com/refcardz/struts2
 Spring Framework
 http://www.springsource.org
 Apache Flex
 http://flex.org

References ...
 Microsoft Silverlight
 http://www.microsoft.com/silverlight/
 http://silverlight.net/learn/videos/silverlight-videos/
net-ria-services-intro/
 Open Laszlo
 http://www.openlaszlo.org
 Ruby on Rails Video: Creating a Weblog in 15 Minutes
 http://www.youtube.com/watch?v=tUH1hewXnC0
 Yii Framework
 http://www.yiiframework.com
 Zend Framework
 http://framework.zend.com

References ...
 CakePHP
 http://cakephp.org
 Node.js
 http://nodejs.org
 Django
 https://www.djangoproject.com
 Comparision of Web Application Frameworks
 http://en.wikipedia.org/wiki/Comparison_of_web_
application_frameworks

2 December 2005
Next Lecture
Web 2.0 Basics

Web Application Frameworks - Lecture 05 - Web Information Systems (4011474FNR)

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