Saturday, June 29, 2013
INTRODUCTION
These
are components that allow web developers to create server-side scripted
templates that generate dynamic, interactive web server applications. By
embedding special programmatic codes in standard HTML pages, a user can access
data in a database, interact with page objects such as Active-X or Java
components, or create other types of dynamic output. The HTML output by an
Active Server Page is totally browser independent, which means that it can be
read equally well by Microsoft Explorer, Netscape Navigator, or most other
browsers. The code for this scripting can be written in any of several
languages, and is embedded in special tags inside the otherwise normal HTML
code making up a page of content.
The Static
Internet
The
web server did not dynamically generate any part of the sites contents but
simply served requests for static HTML pages loaded from the web server's file
system and sent to the requesting client.
The Dynamic
Internet
Ø CGI Applications
(Common Gateway Interfaces)
It provides a mechanism
by which a web browser can communicate a request for the execution of an
application on the web server. The result of this application is
converted/formatted into a browser readable (HTML) form and sent to the
requesting browser.
Ø ISAPI Applications
(Internet Server Application Programming Interface)
In CGI
applications the web server has to instantiate a new application every time a
request in made. In ISAPI, to relay this
problem having the DLL (Dynamic Link Libraries). Once the ISAPI application DLL is loaded into
memory, it stays in memory. The web
server does not need to load it again.
In addition to ISAPI applications,
ISAPI allows for the development of ISAPI filters. An ISAPI filter is a custom
DLL that is in the same memory space as the web server and is called by the web
server in response to every HTTP request, and it instructs the web server how
to handle the request. A security layer
between the client and the web server it provides page-level security.
Active Server
Pages
Late
in the life of IIS2.0 (Internet Information Server) Microsoft began public beta
testing of a technology whose code name was Denali . This technology is now known as Active Server
Pages.
ASP: A
demonstration
An example of
processing server-side script.
<%@
LANGUAGE="VBSCRIPT" %>
<HTML>
<HEAD>
<TITLE>Sample
ASP</TITLE>
</HEAD>
<BODY>
Good
afternoon. <BR>
Welcome
to the sample. It is now approximately
<%=Time()%>
at the server. Here are a couple of
demonstrations:<BR><BR><BR>
Some
simple text formatting done using HTML:<BR>
<FONT
SIZE = 1>Hello Size 1</FONT><BR>
<FONT
SIZE = 2>Hello Size 2</FONT><BR>
<FONT
SIZE = 3>Hello Size 3</FONT><BR>
<FONT
SIZE = 4>Hello Size 4</FONT><BR>
<FONT
SIZE = 5>Hello Size 5</FONT><BR>
<BR>
The
same text formatting using server-side code:<BR>
<%
For
intCounter = 1 to 5
%>
<FONT
SIZE = <%=intCounter%>>
Hello
Size <%=intCounter%></FONT><BR>
<%
Next
%>
<BR>
</BODY>
</HTML>
The
server accepted the request, ASP.DLL interrupted and executed the server side
script and created HTML. The HTML is
sent to the client, where it appears indistinguishable from straight HTML code.
The ASP Object
Model
ASP
encapsulates the properties and methods of the following. Application, object context, request,
response, server, session objects.
Ø Application
object is an ASP application itself.
Ø Object context
object is a part of the Microsoft Transaction Server and is only interfaced
through ASP.
Ø Request object
represents the way you interact with the clients HTTP request.
Ø Response object
represents your access/control over the HTTP response sent back to the user.
Ø Server object
gives you access to the web server itself.
Ø Session object
holds information that is unique to a specific user's current session on the
web server
ACTIVE SERVER PAGES
Scripting
languages are used to develop interactive web pages. Live script is a script
language developed by the NetScape communications along with the Sun
Microsystems. It consists of limited programming instructions that reside in
the web pages viewed using the NetScape Navigator browser on the client
machine. The main aim of this scripting
language is to solve the dynamic web application problems. The marketing demand on surrounding Java, the
LiveScript was quickly renamed to JavaScript.
With this JavaScript, you could build forms and mortgage calculators and
all sorts of interactive web pages. The draw back for this scripting language
had the scripting host.
VBScript
is developed by the Microsoft for its own. VBScript means Visual Basic,
Scripting Edition. The syntax of the
JavaScript is similar to the Java, but the syntax of the VBScript is same as
Visual Basic.
Client-side
Scripting
How
to include scripting code in the web pages that are viewed by your users. How
the browser recognizes the script is all script is surrounded by matching
<SCRIPT></SCRIPT> tags. The most famous client-side scripting
languages JavaScript, VBScripting, PerlScript.
The
difference between these script languages are shown below:
<SCRIPT
LANGUAGE="JavaScript">
<!--
Function
AlertJS()
{
alert("Hello world.")
}
-->
</SCRIPT>
<SCRIPT
LANGUAGE="VBScript">
<!--
Sub AlertVBS()
MsgBox
"Hello world."
End Sub
-->
</SCRIPT>
<SCRIPT
LANGUAGE="PerlScript">
<!--
Sub AlertPS()
{
$window->alert("Hello
world.");
}
-->
</SCRIPT>
In
the above example <!-- and -- > are the HTML comment symbols.
Server-Side
Scripting
Now
we will learn how to bring the power of scripting to the server and harness it
to dynamically create HTML in reaction to user requests. The server side
scripting pages files having the file extension of .ASP, whenever the browser makes a request
for a file ending with the .ASP file extension, IIS knows to bring ASP.DLL into play to interpreted the result of this
code are placed into the document, which is a simple HTML document before it is
sent to the user.
How
does the ASP.DLL know which code to interpret
the answer to this question is the ASP.DLL interprets all code in a file
that's delimited with <%......%> as being ASP code. We can dynamically
construct not only HTML content but also client-side script code.
Example of this
dynamic form of ASP file is shown here
<HTML>
<HEAD><TITLE>Example </TITLE>
<BODY>
Welcome to dynamic form.
<%
intCmdCount=Request.QueryString("button_count")
if cmdCount<1 then
intCmdCount =1
Endif
if int CmdCOunt>10 then
intCmdCount=10
Endif
For intCounter=1 to intCmdCount
%>
<INPUT
TYPE=button VALUE =Button<%=intCounter%>
onClick="Button<%=int
Counter%>-Click()
<%
Next
%>
<SCRIPT
LANGUAGE="VBScript">
<%
For
intCounter=1 to intCmdCount
%>
Sub
Button<%=intCounter%>-Click()
MsgBox
"You just clicked button <%=intCounter%>
EndSub
<%
Next
%>
</SCRIPT>
</BODY>
</HTML
ASPFunctions
Code
reuse is as important in Active Server Pages as it is in any other form of
application programming. It is possible
with RUNAT attribute of the <SCRIPT> tag.
Extending Active Server Pages
Extending
Active Server Pages applications usually takes the form of instantiating sever
side objects that expose methods and properties that you can access through
your server side code. Once instantiated, a browser capabilities object allows
you to discern details about the user's web browser: what scripting is supports, what platform it is running on,
and so on. This component allows you to dynamically alter your site in response
to the presence or absence of certain browsers. The following table gives the
list of server components discussed in ASP nutshell.
|
Server Component
|
Description
|
|
|
Adds database access to
Active Server Pages Application.
|
|
Browser Capabilities
|
Easily determines the
functionality supported by your user's web browser
|
|
Collaboration Data Objects
for NTS
|
Adds messaging
functionality to web applications. Using the objects that make up CDONTS, you
can create robust, mail enabled group ware applications using ASP. Although
it is a powerful extension to ASP
|
|
Content Linking
|
Maintains a linked list of
static content files. From within these files, the content linking component
allows you to set up easy-to-use navigation from one page to next page.
|
|
Content Rotator
|
Creates a schedule file
containing several pieces of HTML that are alternately placed in your web
site. This component is similar to the AdRotator component but works with
straight HTML content rather than advertisements.
|
|
Counters
|
Maintains a collection of
counters, over the scope of an entire ASP application that can be incremented
or decremented from any where in your web site.
|
|
File Access Components
|
Allows you to access your
local and network file system. It's part of the scripting runtime library
that's installed and registered by default when you install IIS.
|
|
MyInfo
|
Maintains commonly
accessed information, such as the web master's name, address, company, etc.,
from with your web application.
|
|
Page Counter
|
Creates a page counter on
any page on your web site .the page count is saved regularly to a text file.
This allows you to maintain page count information even if the web server is
restarted.
|
|
Permission Checker
|
Checks the permissions on
a given resource on the local machine or the network. This allows you to
determine on the fly whether the current user has permission to see a file.
|
Although
IIS comes with several server components, you also can write your own in any
development language that can create COM objects.
ASP Object Model
You
can share information among all clients of a given ASP application using the
application object this built-in object represents the ASP application itself
and is the same regardless of the number or type of clients accessing the
application and regardless of what part or parts of the application those clients
are requesting.
The
application objects initialization occurs when the first user of your
application requests any file from within the virtual directory that the ASSP
application encompasses. This initialization can be thought of as setting aside
memory for the given ASP application. The web browser instances and initializes
the application object for you. However, you can customize this initialization
by including code in a special optional file called GLOBAL.ASA.
Application
Objects
The GLOBAL.ASA file provides a place
for you to create variables and objects that have application level scope.
|
Application Object Summary
|
|
Properties
None.
Collections
Contents
StaticObjects
Methods
Lock
Unlock
Events
Onstart
Onend
|
Collections References:
Contents
Collection
Syntax:
Application.Contents(key)
The
content collection contains all the application level scoped variables and objects added to the current application
through the use of scripts.
StaticObjects
Syntax: Application.StaticObjects(key)
The Static Objects collection contains
all of the objects added to the application through the use of the
<OBJECT> tag.
Methods References:
Lock
Syntax:
Application.Lock
The
lock method locks the application object prevents any other client from
altering any variables values in the contents collection.
Unlock
Syntax:Application.Unlock
The
unlock method is used to release the application object, so other clients can
alter the contents collection variable values.
Events
References:
OnEnd
Syntax: Application_OnEnd
The
OnEnd event is triggered when the ASP application itself is unloaded from the
web server or when the application is inadvertently stopped for some reason.
OnStart
Syntax: Application_OnStart
The
OnStart event is triggered when the firsr client request is received.
Object Context
Object
An
important addition in Active Server Pages2.0 is the ability to create a
transactional script: one whose constituent code segments all, succeed
completely or fail as a group. ASP application transactions are controlled by
Microsoft Transaction Server (MTS).
|
Object Context Object
Summary
|
|
Properties
None
Collection
None
Methods
SetComplete
SetAbort
Events
OnTransactionCommit
OnTransactionAbort
|
Method References:
SetAbort
Syntax: ObjectContext.SetAbort
Aborts
the transaction as a whole. When it is called the transaction ends
unsuccessfully, regardless of code that has or has not already been processed
in your script.
SetComplete
Syntax:
ObjectComplete.SetComplete
Signals
the successful completion of a transaction. When it is called the code in the
OnTransactionCommit event procedure code is processed it is exists.
Events Reference:
OnTransactionAbort
Syntax:OnTransactionAbort()
The
OnTransactionAbort event procedure is processed immediately if the SetAbort
method of the object context object is called explicitly in scripted code or by
a server component called from the scripted code. If no code calls the SetAbort
method, this event procedure is never processed.
OnTransactionCommit
Syntax: OnTransactionCommit()
The
OnTransactionCommit event procedure is processed immediately if the SetComplete
method of the ObjectContext object is called explicitly if no script is in
scripted code or by a server component called from the scripted code. It also
is called implicitly if no script on the current page called SetAbort method.
Request Object
The
properties, collection, methods and events of the ASP Request object is shown
below:
|
Request Object
Summary
|
|
Properties
TotalBytes
Collections
ClientCertificate
Cookies
Form
QueryString
ServerVAriables
Methods
BinaryRead
Events
None
|
Properties References:
TotalBytes
Syntax:
var=Request.TotalBytes
The
TotalBytes property is a read-only value that specifies the total number of
bytes posted to the web server by the client in the HTTP request body.
Collections References:
ClientCertificate
Syntax: Request.ClientCertificate
The
ClientCertificate collection of the request object access to the certification
fields of the client's digital certificate. ClientCertificates are sent to the
web server when a client's browser supports the Secure Socket Layer.
Cookies
Syntax: Request.Cookies
A Cookie is a small bit of information
that is stored for a set period of time on the client machine, and is stored as
a named value and keyed by the ASP application path.
Form
Syntax: Request.Form
Form
contains name-value pairs sent from a form using the POST form posting method.
Each for element becomes one entry in the form collection.
QueryString
Syntax: Request.QueryString(variable)[(index)|
.Count]
QueryString contains name-value pairs
sent using the form's GET posting method or appended to the end of the URL used
to reference the ASP page. Each name value pair becomes one entry in the
QueryStringCollection.
ServerVariables
Syntax: var=Request.ServerVariables(key)
The
ServerVariables collection contains several predefined environment variables in
the context of the client's specific HTTP request of the web server.
Methods References:
BinaryRead
Syntax:
MySafeArray=Request.BinaryRead(ByteCount)
Here
MySafeArray is used to store the information ByteCount is the number of bytes read using the
BinaryRead method.
Response object
A
response is output to a client from the server, and response object is used to
send this information.
|
Response Object Summary
|
|
Properties
Buffer
CacheControl
Charset
ContentType
Expires
ExpairsAbsolute
IsClientConnected
PICS
Status
Collections
Cookies
Methods
AddHeader
AppendToLog
BinaryWrite
Clear
End
Flush
Redirect
Write
Events
None
|
Properties References:
Buffer
Syntax:
Response.Buffer[=flag]
A
flag to determine whether Response output is buffered until the server script
is finished processing or until a forced buffer output.
CacheControl
Syntax: Response.CacheControl[=Cache
Control Header]
A
flag to determine whether proxy servers can cache ASP generated output.
CharSet
Syntax: Response.CharSet(Charsetname)
It is an HTTP response character set
ContentType
Syntax: Response.ContentType[=strCharsetName]
The HTTP ContentType; text/HTML by default.
Expires
Syntax:
Response.Expires[=number]
It gives minutes before the Asp page content is
expired.
ExpiresAbsolute
Syntax: Reponse.ExpiresAbsolute[=[Date][Time]]
A specific date and time when the cached page
contents are expired.
IsClientConnected
Syntax: Response.IsClientConnected
Whether the client is connected after the last
response.
PICS
Syntax: Response.PICS(PICSLabel)
PICS
is a rating system used voluntarily by site’s to rate the adult nature of
content within the site.
Collections References:
Cookies
Syntax:
Response.Cookies.Item(key)=strCookieValue.
Methods
References:
Add Header
Syntax:
Response.AddHeader Name, Value
Adds
an HTML header to the response.
AppendToLog
Syntax:
Response.AppendToLog string
Appends a String of up to 80
characters, not including any commas, to the log file for the response.
BinaryWrite
Syntax:
Response.BinaryWrite data
Writes data to
out put with out any character conversion.
Clear
Syntax:
Response.Clear
Clears
the current buffered contents.
End
Syntax:
Response.End
Ends server
script processing and forces out put of buffered contents .
Flush
Syntax:
Response.Flush
Forces
out put of buffered contents and ends keep-alive requests for the page.
Redirect
Syntax:
Response.Redirect URL
Redirects the connection to a different URL.
Write
Syntax:
Response.Write variant
Writes
information directly to the HTTP response body.
Server
Object
The server object
is used to create instances of server component objects, which can the be used
with in another component or with in an
ASP page.
|
Server Object
Summary
|
|
Properties
ScriptTimeout
Collections
None
Methods
CreateObject
HTMLEncode
Mappath
URLEncode
Events
None
|
Properties References:
ScriptTimeout
Syntax: Server.ScriptTimeout [=NumSeconds]
The default time out value is 90 seconds.
Methods References:
CreateObject
Syntax:
SetObjMyObject=Server.CreateObject(ProgID)
Instances an
object on a server.
HTMLEncode
Syntax:
Server.HTMLEncode(string)
Takes a string as a parameter and
returns the same string with HTML encoding.
MapPath
Syntax: Server.MapPath(Path)
Maps
a virtual or relative path to a path relative to the directory of the ASP file
being accessed.
URLEncode
Syntax: Server.URLEncode(string)
Takes a string as a parameter and
returns the same string with URL encoding.
Session
Object
The session
object manages object instances and variables at
the session
level.
|
Session Object
Summer
|
|
Properties
CodePage
LCID
Timeout
Collections
Contents
StaticObjects
Methods
Abandon
Events
Session-OnEnd
Session-OnStart
|
Properties References:
CodePage
Syntax: Session.CodePage(=CodePage)
Sets code page to be used for the ASP file.
LCID
Syntax:
Session.LCID(=LCID)
LCID represents
local identifier. This identifier is a standard local identifier used to
display local-specific content.
SessionID
Syntax: Session.SessionID
It uniquely identifies the current user's session.
TimeOut
Syntax: Session.TimeOut(=nMinutes)
The specific time period that determines when the
session ends.
Collections References:
Contents
Collection
Syntax: Session.Contents(key)
Contents all of the variables and
objects added with session-level scope through script.
Static Objects
Syntax: Session.StaticObjects(key)
Contains
all of the objects with session level scope that are added to the application
through the use of the <OBJECT> tag.
Methods References:
Abandon
Syntax: Session.Abandon
Releases a memory used by the web
server to maintain information about a given session.
CONCLUSION
MicroSoft
created ASP in answer to the need for a scalable and efficient web server
application technology, that is also relatively safe. ASP is fairly simple to
use, and all of the applications can actually be created with server side
script using languages like JavaScript/JScript or VBScript. If some
functionality is needed that can’t be provided by scripting, ASP components can
be used. ASP pages are created with a default extension of .ASP. When IIS gets a
request for a page with an .ASP extension, the web browser access and compiles
the script then script contained within the page and loads the compiled code
into memory. The script then performs some processing, which usually generates
HTML that is then written out to the ASP page.
Thanks for sharing useful information. I learned something new from your bog. Its very interesting and informative. keep updating. If you are looking for any Data science related information, please visit our website Data science training institute in btm layout
ReplyDeleteSuch a wonderful post..
ReplyDeleteThanks for sharing with us,
We are again come on your website,
Thanks and good day,
If you need any logo then,
Please visit our site,
buylogo
Thanks for the post. It was very interesting and meaningful. I really appreciate it! Keep updating stuffs like this.
ReplyDeleteBig Data Hadoop Training In Chennai | Big Data Hadoop Training In anna nagar | Big Data Hadoop Training In omr | Big Data Hadoop Training In porur | Big Data Hadoop Training In tambaram | Big Data Hadoop Training In velachery
Hey everyone.
ReplyDeleteWe are giving you the big best offer to buy logo design for your business with 80% off I expect You will be happy with us.Logo Designers
when I visit this helpful content I realized that this is really useful for me thanks for sharing with us...!
ReplyDeletewe design websites & logos with a guarantee also with a discount are you guys interested in?
Logo Designers