ASP theory

7/30/2019 ASP theory

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Minder Chen 1998-2002 ASP - 1

Active Server Pages

Minder Chen, [email protected]


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Creating ASP Page

ASP uses the delimiters to enclose script commands.

By default, the primary scripting language is VBScript.

test.asp

This page was last refreshed on .

The VBScript function Now returns the current date and time.

This page was last refreshed on 9/11/98 4:30:00 PM.

This page was last refreshed on

9/11/98 4:30:00 PM.

Interpreted ASP code:

An HTML document.

Rendered

via abrowser


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The Active Server Pages Model

Brows

er

Web Server

(IIS)

Active

Server

Page

ASPInterpreter:

Process

ASP

Scripting

Statements

An ASP script begins to run when a browser requests a .asp file from

your Web server.

Your Web server then calls ASP, which reads through the requested

file from top to bottom, executes any ASP statements, and sends an

HTML page to the browser.

.asp files


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ASP Scripting

The first line in an .asp file specifies the

scripting language for the page. For example,

the following first line in .asp file specifies thatthe script is VBScript:

Without a language tag, script in the file isprocessed as the default language (VBScript by

default.)

Active Server Pages can provide a scripting

environment for a number of other scriptinglanguages, including Jscript and others.


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Hello.asp: Display Information

Hello World Example

The end of

script

section

The start of the

script section

Build-in

Object

Argument

Hello World Example

Hello World!

Returned HTML Document

method


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Hello2.asp

HELLO WORLD

Hello World!

http://localhost/asp/hello.asp

HELLO WORLD

Hello World!

Hello World!

Hello World!

Hello World!

Hello World!

Return HTML Source Code


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Hello3.asp


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Hello4.htm: Sample JavaScript Code

HELLO WORLD

document.write("

Hello world! -- From Client-Side Scripting!")

Hello World! -- From HTML


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Data Types Variables: Simple variables and Array variables

VBScript subsumes all categories of data under one name

called a Variant. At a basic level, Variants contain either string or numeric

data.

String data is used for text, while numeric data contains

only numbers.

Variant data can be further classified into subtypes. For

example, you can have numeric data that represents

currency, or a date or time, and the Variant will interpret

the data accordingly.

You can use the data type conversion function for data

type conversion. For example, CIntfunction to forceconversion of an expression to the Variant of subtype

Integer.


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Data Types

Empty Variant is uninitialized. Value is 0 for numeric variables or a zero-

length string ("") for string variables.

Null Variant intentionally contains no valid data.

Boolean Contains either True or False.

Byte Contains integer in the range 0 to 255. Integer

Contains integer in the range -32,768 to 32,767.

Currency

-922,337,203,685,477.5808 to 922,337,203,685,477.5807. Long

Contains integer in the range -2,147,483,648 to 2,147,483,647.


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Data Types

Single Contains a single-precision, floating-point number in the range -

3.402823E38 to -1.401298E-45 for negative values and1.401298E-45 to 3.402823E38 for positive values.

Double Contains a double-precision, floating-point number in the range

-1.79769313486232E308 to -4.94065645841247E-324 for negativevalues and 4.94065645841247E-324 to 1.79769313486232E308 for

positive values. Date (Time)

Contains a number that represents a date or time betweenJanuary 1, 100 to December 31, 9999.

String Contains a variable-length string that can be up to

approximately two billion characters in length.

Object Contains an object.

Error Contains an error number.


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Declaring Variables VBScript implicitlycreates a variable the first time that it encounters an

unrecognized string of characters that could be a variable name.

The Option Explicit statement informs VBScript to generate an error if itencounters an undeclared variable. The Option Explicit statement shouldbe the first line of code in a script that uses variables.

Dim varname

Dim a

A variable name: Must begin with an alphabetic character.

Cannot contain an embedded period.

Must not exceed 255 characters.

Must be unique.

Is not case-sensitive.

Constants: Const CorpName = "Volcano Coffee Company"

Const HousePayment = 1500


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Exercise: Variable.asp

Variables

Have to be the

first line

Declare a variablewith a data type

is not allowed:

Dim x as Integer


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Response Object: Write Method

Hello World

Hello World

Message


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Math OperationsMath Operations

7 + 3 = 10

7 - 3 = 4

7 * 3 = 21

7 / 3 = 2.33333333333333


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Decision Making and Branching To vary the flow of a script, you use conditional statements (also known as

controlstructures) to makes decisions during program execution.

The conditional statements include test expressions that are evaluated as

the program runs and, based upon their results, control the program flow. The two control structures that you will learn include

IfThenElse

Select Case.

C


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Control Flow

True Block

False Block

M ki D i i U i S l C


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Making Decision Using Select Case A Select Case structure works with a single test expression that is evaluated

once at the top of the structure.

The result of the expression is then compared with the values for each Casein the structure. If there is a match, the block of statements associated withthat Case is executed.

Use the Case Else statement to handle any condition that did not match aspecified case.

E l


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Example

Dim Color, MyVar

Sub ChangeBackground (Color)

MyVar = lcase (Color)Select Case MyVar

Case "red" bgColor = "red"

Case "green" bgColor = "green"

Case "blue" bgColor = "blue"

Case Else bgColor = "white"

End Select

End Sub

L


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Loops

Loops

1

2

3

4

5

10

8

6

42

0

L St t t


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Loops Statements

VBScript includes the following looping

constructions:

Do...Loop: repeats statements while or until a test

condition is met.

For...Next: repeats statements a specified number of

times.

For Each element In group Next: repeats statements for

each occurrence of a specific item in a specified group.

L D Whil L


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Loop: Do While Loop

Counter = 1

Counter = 2

Check condition at the

beginning of the loop

D L Whil


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Do Loop While

Dim Counter

Counter = 1

Do

Response.Write "Counter = " & Counter & "
"

Counter = Counter + 1

Loop While Counter < 3

Check condition at

the end of the loop

D U til


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Do Until

To check the test condition at the beginningof the

loop, change the following statement:

Do While Counter=3 Loop

To check the condition at the endof the loop,

change the following statement:

Do Loop While Counter=3

F I t D t P i


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Form Input Data Processing

form4.htm

Form Input

Name:

answer04.aspForm Input Processing

E i F I t D t P i


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Exercise: Form Input Data Processing

Form htm


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Form.htmOrder

Sample Order Form

Please fill out this form, then click Submit:

First Name:

Last Name:

Title: Mr.

Ms.

http://127.0.0.1/vbscriptlab/form.htm

Response asp


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Response.asp

Response.asp File

Order Received

Response2 asp


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Response2.asp

Response.asp File

Order Received

Mr.

Ms.

Change the action attribute

of form.htm to response2.asp

and save it as form2.htm

Exercise: Calculator


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Exercise: Calculator

Operator can be: +, -, *, /

Check divide-by-zero error

A*B=600

Cal.htm

Cal htm


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Cal.htmCalculator

First Number:

Operator is:

+

-

*

/

Second Number:

Cal asp


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Cal.aspCalculator


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Continued...Select Case Request.Form("op")

Case "+"

C=A+B

Response.write "A+B=" & C

Case "-"C=A-B

Response.write "A-B=" & C

Case "*"

C=A*B

Response.write "A*B=" & C

Case "/"If B0 Then

Temp=A/B

C=Round(Temp,2) ' Round it to 2 decimal places

Response.Write "A/B=" & C

Else

Response.write "The second number cannot be zero." & "
"

Response.write "Use BACK navigation button to change it!" & "
"End If

Case Else

Response.Write "You need to choose an operator"

End Select

%>

Exercise: sub1 asp


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Exercise: sub1.asp

Subroutine

Subroutine

sub2.asp

Scope of a Variable


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Scope of a Variable

If a variable is declared outside of a procedure,

it is visible throughout the program.

If a variable is declared inside a procedure, it is

only visible inside that procedure.

The range of a variables visibility is called its

scope.

Functions


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Functions

Function fName(arg1, arg2, ...)

...

fName = expression

...

End Function

Create a variable with the same name as the Function.

Assign the return valueto that variable.

Arguments, including constants, variables, and

expressions, are passed to the Function procedure,

which can then use the arguments.

Function arguments are placed inside parentheses. If no

arguments are passed, empty parentheses are required.

Functions: temp2 asp


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Functions: temp2.asp

Temperature


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Object, Property and Method You can create an instance of an object by using the

Server.CreateObject statement.

An object can contain callable program code called methods and data

called properties.

Dot notation

objectName.propertyName

objectname.methodName

objectname.methodName(arg1, arg2, )

QueryString Collection


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QueryString Collection

The QueryString collection retrieves form values

passed to your Web server using HTTP GET methodor retrieves variable-value pairs set as text followed aquestion mark in the request URL.

Example:

Process Input Data from the QueryString


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Process Input Data from the QueryString

If the user typed Jeff, Smith, and 30, then the following URLrequest would be sent to the server:

http://scripts/profile.asp?firstname=Jeff&lastname=Smith&age=30&userstatus=new

profile.asp:

Hello, .

You are years old. Hello, Jeff Smith. You are 30 years old. This is your

first visit to this Web site!

Multiple Values of a Variable


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Multiple Values of a Variable The QueryString collection has an optional parameter

Counterthat you can to count the number of times that aspecific variable appears.

A request of a form containing a list box with multiple items:

http://scripts/list.asp?food=apples&food=olives&food=bread

Command to count multiple values:

Request.QueryString("food").Count To display the multiple values types, List.asp could contain the

following script:

The preceding script would display:applesolives

bread

Use ADO


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Use ADO

The Database Access component uses Active Data

Objects (ADO) to provide easy access to

information stored in a database that complies withthe Open Database Connectivity (ODBC) standard.

You will learn how to extract data using the SQL

SELECT statement and create an HTML table todisplay the results.

Identify the Database


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Identify the Database

Before using a database with the Database Access component, you must

identify the database in the ODBC application in Control Panel. In this

example, you will use a Microsoft Access database that is provided with

the ASP sample Web site.

At the computer running your Web server, open Control Panel.

Double-click the ODBC icon, and then click System DSN.

There are two types of data sources: User, which is available only to you,

and System, which is available to anyone using the computer. Datasources for use with the Web server need to be of the System type.

Click Add, choose the Microsoft Access Driver, and then click Finish.

In the Data Source Name box, type ASP Tutorial DB, and then click

Select. Select the c:\Webshare\asp\AdvWorks.mdb file and click OK.

Click OK to close the dialog boxes.

Set Up ODBC Data Source


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Set Up ODBC Data Source

Deptlist.asp


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Deptlist.aspDepartment ListingDepartment List

:

Using Table


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Using Table

OLE DB Connection String


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OLE DB Connection String

Microsoft Access

Provider=Microsoft.Jet.OLEDB.4.0;Data

Source=phys ical path to database f i le

Microsoft SQL Server

Provider=SQLOLEDB.1;Data Source=path to

server Oracle

Provider=MSDAORA.1;Data Source=path toserver

Microsoft Indexing Service

Provider=MSIDXS.1;Data Source=path to indexfi le

Insert


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Insert

Update and Delete


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Update and Delete

ASP and Session Management


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ASP and Session Management

Hypertext Transfer Protocol (HTTP) is a stateless protocol. Each

browser request to a Web server is independent, and the server

retains no memory of a browser's past requests.

The Session object, one of the intrinsic objects supported by ASP,provides a developer with a complete Web session management

solution.

The Session object supports a dynamic associative array that a

script can use to store information.

For each ASP page requested by a user, the Session object will

preserve the information stored for the user's session. This

session information is stored in memory on the server. The user is

provided with a unique session ID that ASP uses to match user

requests with the information specific to that user's session.

A session is terminated

when you close the browser.

Err.asp


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Err.aspThe Err Object

Err.Description =Division by zero

Err.Number=11

Err.Source=Microsoft VBScript runtime error

Err.HelpFile=

Err.HelpContext =0

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