Web Application Architecture - Web Design and Development - Lecture Slides, Slides of Web Design and Development

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Web Application Architecture

Client Server Model

Client Applications (Software)

• Provides user interface
• Stores some settings
• Can do some data processing
• Little to no application data

storage

• Same view of data no matter where you login

Client-Server Advantages

• Centralized Data Storage
• No data redundancy (no duplication of data)
• Reduces data dependencies
  • If data is stored on each user’s system and each system is different than data depends on how the user system is designed
  • Data can not be shared easily if such dependencies exist

Classic Example:

Early Banking Systems

The Obvious Future:

• Change the LAN to a wide area network

covering all the branches.

• Get rid of the individual servers at each

branch

• Have clients connect to central server where

ALL the banking data is stored.

Classic Example:

Early Banking Systems

The Obvious Problems:

• Large banks could have thousands of tellers

connecting to the central server.

• Combining data from all branches requires

severs with lots of storage capacity.

• Branch data could be stored in different

formats.

• Lack of Standardization.

3-Tiered System

• Database Tier (Database Server)
  • Data storage and low level data manipulation
• Server Tier (Application Server)
  • Manage client connections and data processing
• Client Tier (Client Software installed locally)
  • User interface and some data processing

Advantage of 3-Tier Systems

• Central Database Server accessed by multiple Application Servers
• In turn, each Application Server could independently manage thousands of users
• Database Server is specially designed to do its job
  • Database Operations: Update, Insert, Remove, etc.
  • Lots of disk storage and memory needed
• Application Servers can be added to support more users or DIFFERENT APPLICATIONS - Server Operations: Complex application-dependent computations - Lots of processor power needed

WWW – Ultimate Client-Server System

• Already Standardized
• Built on the Widest Area Network you could

imagine, i.e., The Internet

• Standardized Clients that are free to use
  • IE, Firefox, Safari, etc.
• Lots of Servers already in place
  • Apache, Windows Server (IIS), etc.
• Database Servers
  • Umm, this was initially missing

First Web Applications

• 1993 – Rob McCool proposed a framework called
  • CGI (Common Gateway Interface)
• Data passed from a web browser to the server
  • GET - passed via URL variables
  • POST - passed via HTML forms
• Web server daemon (httpd) could then make remote system calls
• Example
  • Web server could run a C++ program and write the output to public HTML folder
  • Web server would send response back with location of the output.

First Web Applications

Problem:

• To develop web applications you need to

know

• Exactly how your server is configured
• HTML forms
• GET and POST conventions
• C++ database libraries
• SQL language
• Getting all these things to work together is a

pain in the ***.

First Major Improvement

• 1995 – JJ Allaire developed “a hack” that allowed a

web servers to communicate with other systems, namely a database system.

• Key:
  • Instead of using “a middle-man” C++, Perl, Java, etc.
  • Developer could directly add code to the their web pages
  • Using a special Markup Language, this code could be embedded in any web page.
  • Worked seamlessly with HTML forms
  • Server process code directly

ColdFusion Example

Customize Site

light color
dark color

#getTokensMinusArg('inputs',droplist)#

ColdFusion

• The term Cold Fusion refers to a nuclear reaction that can occur at room temperature
• In the 1980’s it was believed that Cold Fusion was a physical possibility.
• If Cold Fusion could be achieved then almost unlimited power could be generated by a reaction you could perform in your own kitchen.
• JJ Allaire aptly named his product ColdFusion because he believed it would be as great as real “Cold Fusion.”
• He was right, but…