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Bài giảng Web technologies and e-Services - Bài 6: Web development models - Trường Đại học Bách khoa Hà Nội

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Web Development Models  
Content  
• Web Application Architecture: client-server  
• Programming Languages on client side  
• Programming Languages on server side  
• 3-tier architecture and MVC model  
Client-Server Model  
Client side  
Server side  
Server Roles  
§ Manage and store data, including:  
§ User data  
§ Application data  
§ Provide processing services for data  
§ Centralize data  
§ Manage user authentication, authorization mechanisms  
via login function  
Client Roles  
§ Provide user interface  
§ Can store some small data (using cookie)  
§ Can process data (check validity of data that are  
entered by users  
§ Thin client: only provides user interface, centralize data processing  
on server side  
§ Thick client: realizes data processing on client side  
§ Can be accessed from everywhere with minimal  
software installation  
Client-Server Advantages  
§Centralized storage and processing.  
§No data redundancy  
§Enhance the ability of sharing data  
§If data are distributed on multi-systems of users, it will cause difficulties in  
sharing the data because each system has its own database architecture  
3-Tier Architecture  
§ Database Tier (Data Access Layer)  
§ Stores and accesses data in low-level  
§ Server Tier (Business Logic Layer)  
§ Manages application connections and process ta  
§ Client Tier (Presentation Layer)  
§ Provides interface and processing  
Presentation  
Layer  
Business  
Logic  
Data  
Access  
Layer  
Layer  
3-Tier Architecture Advantages  
§Centralized Database can be accessed by many servers at the  
same time  
§Allow load balance of user connections on many application servers  
§Data Access Layer is consistently designed with hardware in order  
to serve specific its tasks:  
§Data manipulations: update, insert, remove, etc  
§Need more reliable hard drives  
§Business Logic Layer are designed to provide connection points  
for user connections and run multi-applications  
§Need more computing power of CPU  
Programming Languages  
Client  
Server  
Database  
Html  
Java, Ruby  
Visual Basic  
PHP, Perl  
Python  
SQL  
JavaScript  
Flash  
NoSQL  
Client Programming Language  
JavaScript  
§Event Handling  
§Statements (like C / Java)  
§Operators  
§Variables global (default)  
§Or local (e.g. var x = 1)  
§Types can change  
§Eg. x = 1; x = ‘Hello’  
§Function definition (reuse)  
§Message Alerts  
§Page element access with Document Object Model  
§Views HTML page as a tree of elements  
Hello World Example  
• This provides an annoying popup – try it!  
<html>  
<body>  
<a href="http://www.google.co.uk"  
onMouseOver="(alert(  
'Follow link to search on Google') )">  
Search on Google  
</a>  
</body>  
</html>  
Server Programming Language  
§Java – uses Java servlets, Java Server Pages (JSP) and Java  
Beans.  
§Ruby on Rails – uses ruby programs and Embedded Ruby (ERB).  
§Visual Basic – Uses VB programs and Active Server Pages (ASP).  
§Others:  
§PHP (Personal Home Page – originally)  
§CGI (Common Gateway Interface)  
§Perl (Named after the parable of the pearl)  
§Python (Named for the Monty Python skits)  
§Tcl (Tool Command Language)  
PHP  
• Very c-like  
• Classes, etc., work very much like C/C++  
• Designed to work in the world of HTML  
• Is run-time interpreted by the web server  
Simple PHP Example  
§ PHP is meant to be invoked inline with content Page “escapes” into and out of a regular  
html document  
§ File extension is .php (was .php3 for version 3)  
<html>  
<head><title>Test page</title></head>  
<body>  
The time is now  
<?php echo date();?>  
<hr>  
</body>  
</html>  
JSP Example  
<html>  
<head><title>Hello JSP</title></head>  
<body>  
<p> Hello World:  
<%= new java.util.Date() %>  
</p>  
</body>  
</html>  
Produced  
MVC Development Model  
§ Architectural Pattern from Smalltalk (1979)  
§ Decouples data and presentation  
§ Eases the development  
MVC – The Model  
§ The “Model” contains the data  
§ Has methods to access and possibly update it’s contents.  
§ Often, it implements an interface which defines the allowed model  
interactions.  
§ Implementing an interface enables models to be pulled out and  
replaced without programming changes.  
MVC – The View  
§The View provides a visual representation of the model.  
§There can be multiple views displaying the model at any one time.  
§For example, a companies finances over time could be represented as a  
table and a graph.  
§These are just two different views of the same data.  
§When the model is updated, all Views are informed and given a  
chance to update themselves.  
MVC – The Controller  
§ It interprets mouse movement, clicks, keystrokes, etc  
§ Communicates those activities to the model – eg: delete row,  
insert row, etc  
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