Chapter 8 Objectives

1
Chapter 8 Objectives

• Evolution of Client/Server Architecture
• Web-Based Client/Server Applications
• Essentials of ASP Programming and Editing
• Selection of ASP Tools

2
Client/Server Architecture

• Two components
• Client client computers and their software
• Server includes both hardware and software

Client machines send requests to server
Server processes request
Server returns results to client
3
One-Tiered Architecture

• Server mainframe or minicomputer
• Dumb terminals
• No internal processing power
• No storage capacity
• All processing, calculation, storage done on
  mainframe
• Disadvantages
• Single centralized processor
• Lacks flexibility and scalability

4
Two-Tiered Architecture

• Server mainframe or minicomputer
• Personal computers
• Processing tasks divided
• Applications run on PCs
• Data stored on mainframes
• Disadvantages
• Complex applications are large
• Client PCs become fat

5
Three-Tiered Architecture

• Server mainframe or minicomputer
• Personal computers
• Application server
• Middleware
• Provides applications
• Acts as transaction monitor
• Stores data
• Advantages
• Thin client

6
Web-Based Architecture
7
Web-Based Client/Server

• Advantages over LANs and WANs
• No geographic boundaries
• Accessible wherever Internet connection available

8
Browser Presentation Layer(p.186)

• Human-to-computer interface
• Possible elements
• Home page with welcome message
• Product pages with buy buttons
• Buy buttons linked to product page
• Order form
• Shipping information

9
Application Server Layer

• Middle layer
• Web server takes requests from client browser
• Forwards requests to the database
• Server collects responses from database
• Passes responses to client browsers
• Building an application server layer
• Install a Web server
• Connect the server to the Internet
• Create a virtual directory for the Web server
• Write a Web client/server database application
  with HTML and DHTML

10
Database Layer

• Stores and retrieves data
• SQL requests received from Web server
• Database app stores data, processes results
• Sends results to server
• Server forwards results to client browsers
• Building a database layer
• Develop database app on the server computer
• Create DSNs for the user and system
• Or Create OLE DB (Object Linking and Embedding
  Database Microsoft standard)

11
Impact of Applications

• School sites
• Registration
• Check schedules, grades, exams
• Business-to-business (B2B)
• Supply chain management
• Business-to-consumer (B2C)
• Online retailing like Amazon.com
• Consumer-to-consumer (C2C)
• Online auctions like eBay

12
Development of Applications

• Browser presentation layer
• HTML
• Application server layer
• ASP, Visual Basic, VBScript, Java, JavaScript,
  Coldfusion, CGI, Perl
• Database layer
• Web-enabled database software
• Access, SQL Server, Oracle
• DSNs or OLE DBs
• Enable database access through application layer

13
ASP ProgrammingStudy pp.198-203

• Secure, server-side scripting
• Viewable with any browser
• Open development environment combines
• Scripting
• Pre-built objects
• ASP delimiters lt . . .gt
• Five primary ASP objects

14
Request Object

• Purpose to get information from the user
• Submits info to Web server
• Basic data collection functions
• Form
• QueryString
• ServerVariables
• Cookies

15
Response Object

• Purpose to send information to the user
• Delivers to client browser
• Basic functions
• Changing cookies
• Controlling properties of objects
• Controlling actions of objects

16
Server Object

• Purpose to control connections to external
  components
• Used in nearly every ASP file
• Supports only one property
• ScriptTimeout
• Determines maximum time an ASP file can take to
  complete an execution

17
Session Object

• Purpose to store information about and change
  settings for the users current Web-server
  session
• Automatically created when new visitor arrives at
  application page
• Enables application to keep track of visitors

18
Application Object

• Purpose to share application-level information
  and control settings for the lifetime of the
  application
• Created at Web server when you create a virtual
  directory for the application

19
ActiveX Data Objects

• Interface with other relational databases
• Use ODBC
• Three objects
• Connection
• Recordset
• Command