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Amélie Cordier, January 2011
This handout is strongly inspired by the MIF13 course of Lionel Medinihttp://www710.univ-lyon1.fr/~lmedini/MIF13/
Discovering the existence of numerous tools to help us designing Web applications◦ No more developments from scratch◦ No more waist of time◦ Real-world application development conditions
Knowing of to organise the various tools◦ Languages / IDE◦ Type of functionalities◦ Compatibility (or not!)
Knowing of to choose a tool (a set of tool) according to the requirements the application
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A Web applications uses external code to perform specific services◦ Security?
◦ Persistence?
◦ ...
Who controls the workflow?◦ In general: your code? Someone else code?
◦ In classical programming? Where is the main?
◦ In MVC? Who handles the controller?
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Main idea: REUSE
Same idea than in classical design◦ Examples: AWT, Swing
Specificities of the Web tools:◦ Numerous
◦ Heterogeneous
◦ More frameworks
Question: what tool shall I choose? How?
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A library is a set of components designed to perform specific functionalities
Libraries for the Web◦ Most of them are dedicated to interface components
◦ AJAX communications
◦ Server-side specific libraries (security)
How to choose a library?◦ Support of the community, liveliness
◦ Adapted to other tools deployed within the application
◦ Should be transparent for the end-user
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Persistence◦ Java: ORMs, JPA
◦ PHP & MySQL: Flat-file SQL
Security◦ Java: WebCastellum
Authentication◦ Java: Jguard, JXplorer (LDAP support)
◦ PHP: PHP OpenID Library
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Tag JSP: JSF
Templates for Web Sites◦ Basic design: often replaced by CSS
◦ Page components
Dynamically managed
Examples: datasets, forms, menus
JavaScript◦ Interface components
◦ Programming components
XSLT transformations
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JavaScript libraries to help coding◦ Swallow structure◦ Only usable for small applications
Server-side tools to generate pages associated to libraries◦ Implies to have a good structure of the application
Examples:◦ Generic: Jquery, SAJAX, DHTMLX, JsHTTPRequest◦ Java: JSP Tags Library◦ PHP: XAJAX, PhpLiveX◦ .Net: ASP.Net AJAX, ...
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Dedicated to a specific programming language
Use a complier to generate JavaScript code◦ Clearer and cleaner code
◦ Client-side code not mastered
Examples:◦ Java: DWR, GWT, IceFaces
◦ Python: Pyjamas
◦ .Net: ASP.Net AJAX
◦ ...
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Description:◦ Components for Web application generation
◦ Components for Asynchronous HTTP communication
◦ Compiler Java to JavaScript
◦ Availability of an extensions library (GWTexT)
Website:◦ http://code.google.com/webtoolkit/
JavaDoc:◦ http://google-web-
toolkit.googlecode.com/svn/javadoc/1.6/index.html
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Remark: a Web Server is a Framework!
A Web framework is an additional abstraction level with regard to the Web server◦ Pattern MVC
◦ AJAX-oriented
◦ Handle additional services: transactions, security, communications with distant objects, ...
◦ Dedicated to a specific purpose: business, communication between users, teaching, data sharing, ...
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Security◦ Authentication, user-rights management, roles management,
access limitation
Connexion with databases◦ Standardized API, ORM, transactions, versions management
URL re-writing◦ Avoid CGI-URL◦ Example : /page.cgi?cat=science&topic=physics =>
/page/science/physics
Templates Web◦ For common page structures◦ Examples: data tables, charts, ...
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AJAX
Automatic settings◦ Using introspection to generate page elements
◦ Example: using an ORM in order to handle automatically object persistence
Web services◦ Generate outputs as web services between the application
layer and the view layer
◦ Often linked to a template engine
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Issues:◦ How to organise all the servlets and JSP of an application?
◦ How to manage the control-flow of the application?
An historical viewpoint:◦ 1. JSP everywhere
◦ 2. Servlets for control-flow, JSP for treatments
◦ 3. Model MVC push-based
◦ 4. Model MVC pull-based
Additional reading:◦ http://struts.apache.org/1.x/userGuide/introduction.html
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Definition:◦ A controller uses actions in order to compute contents
◦ Contents are pushed to the view layer
Examples:◦ Java: Struts
◦ Python: Django
◦ Ruby: Ruby on rails
◦ PHP: Symfony, CakePHP
◦ .Net: ASP.Net MVC
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Definition:◦ The view “pull” contents of several controllers, each one being
dedicated to a specific task
◦ Several controllers can contribute to the creation of a single view
◦ Example: use-case controllers
Examples:◦ Java: Struts2, Tapestry, JBoss Seam
◦ Python: Zope
◦ .Net: .NetNuke
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Description:◦ MVC Framework◦ Created in May 2000 by Craig R. McClanahan◦ URL: http://struts.apache.org/◦ Javadoc: http://struts.apache.org/1.x/struts-core/apidocs/
Content:◦ One main controller, plus additional specific controllers◦ A library of specific JSP tags◦ A tool for forms management◦ A mapping between forms and Java objects◦ A validation tool for forms◦ A template engine (Tiles)◦ ...
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Controller◦ ActionServlet (main controller): catch requests and dispatch them to
the actions, on the basis of the URLs (struts-config.xml)
◦ Actions (secondary controllers): manage the communication with the model and send results to the view
Model◦ Any class provided it is known by the actions
◦ JavaBeans: standardisation of the properties accessed by the view
View◦ Most of the time: JSP displaying the results of the treatments made
by the model
◦ Possibilities of extensions: JSF, AJAX, etc.
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A comparison of several web application frameworks
http://en.wikipedia.org/wiki/
Comparison_of_web_application_frameworks
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Collaborative tools (user management)
Document management tools◦ Workflows
◦ Storing and publication of different kinds of contents
◦ Page templates and WYSIWYG editors
◦ A lot of additional modules for specific purposes
Examples:◦ PHP: SPIP, PHP-Nuke, Joomla!
◦ Python: Plone
◦ Java: OpenCMS, AlFresco
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Main idea: combining several contents from various applications in the same web interface.
Often associated to the notion of portal
Examples:◦ University portals (do you have one?)
◦ IGoogle
◦ NetVibes
Technologies:◦ Java: WSRP
◦ PHP: PhpPortlets
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Idea: connecting an application to a well-know application
Examples:◦ Google, FaceBook, YouTube, Ebay
Advantages:◦ A quick way to improve applications
◦ Enable one to attract more users
Additional reading:◦ http://www.programmableweb.com/apis/directory
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Reuse as a design principle◦ Objective: reduce the development to the business logic
Specificity of the Web tools◦ A lot of tools◦ Quick evolution of technologies and trends◦ Several technologies for a single application Hard to master
Hard to implement and to maintain
Libraries and / or framework? ◦ Importance of the analysis phase when designing a new
application◦ What are the needs and requirements?
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Compatibility issues◦ Between tools
◦ With Web Browsers
◦ With the other systems with which you want to connect your application
Warning: try to estimate the integration time when reusing components!
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What is the gain: services / complexity of the tool?
Is the framework designed for your purpose? ◦ Do not use a framework designed for document management
if you want to develop an application for communication between users!
Evolution issues◦ Scalability
◦ Integration of new services
◦ Integration of forthcoming technologies
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Modularity issues◦ Think about the components of your application
◦ Work on a detailed analysis of the project before choosing the technical solutions
◦ Search for existing solution (in order to reuse them) instead of implementing everything
What if the interface of a library does not match your requirements?◦ Should you modify your specifications?
◦ Can you use an adapter pattern?
◦ Is it the good library?
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Why should you use standard solutions?◦ If you want to integrate your application with existing
applications
◦ If you want other applications to connect with your application
◦ In order to foresee the possibility of changing the interface
RIA / RDA
New browsers / Mobile browsers
Web services
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Web 2.0 and 3.0 ◦ Social◦ Collaborative◦ Semantic (including non-textual contents)
Dynamic Web◦ VOD◦ Synchronous communication (RSS, Twitter)◦ Web conferences
Mobility◦ Mobile platforms◦ Geo-localisation (FourSquare, GoogleSites)◦ Mobile phones features (GPS, barcode reading, Googles)◦ ...
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HTML 5◦ Standards well-established◦ Advanced tools for presentation◦ Support for various (and numerous) types of content◦ Strong interactions with contents◦ Better interactions with users
Examples◦ http://www.youtube.com/watch?v=OxoFcyKYwr0◦ http://people.opera.com/howcome/2010/forms/◦ http://www.youtube.com/watch?v=EdDc7sWjCL4
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