A Brief Intro to ASP and VBScript
 | Although there are a number of ways to run "programs" on a web server (specifically CGI-based programs written in Java, C, and VB), scripting has become a popular technique. | ||||||||
| Scripting is easy to use for developing relatively complex applications. | ||||||||
| Key elements of scripting:
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| The scripting engine must be able to...
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| Scripting languages come in a variety of syntax...VBScript, JavaScript, Cold Fusion (primarily for database interaction) |
Following provides an overview of server-based scripting...
CGI (Common Gateway Interface)
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The protocol standard that describes/defines how web browsers, web servers, and programs on a server can communicate. | ||||||
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When a web page is requested (i.e., a URL is submitted) information is sent to the browser including:
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The web server can pass this information to programs running on the server (e.g., "CGI programs"). | ||||||
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The programs forward HTML to the web server which is sent back to the browser. |
Things to note about CGI...
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It is NOT a programming language. |
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It IS a standard for how things happen between web servers and applications. |
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Historically, Perl was the first language to popularly implement CGI capabilities in commercial applications. |
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CGI can be implemented with C, Java, Perl, PHP, and other executable and interpreted scripting languages. |
Active Server Pages (ASP)
A Microsoft technology for building CGI-based web server applications, briefly...
| Originally intended for IIS (Internet Information Server) and PWS (Personal Web Server) environments (there is a product for UNIX called ChiliSoft that supports ASP). |
| Built on the Microsoft COM/DCOM technology, ASP is an object technology. |
| Integrates easily with other COM/DCOM technologies such as ADO for databases. |
| Is implemented with VBScript and/or JavaScript (JScript). |
ASP Objects...
| Request - get data from the web browser (form, URL) |
| Response - output data to the browser (via HTTP) |
| Server - manage aspects of the server |
| Session - keep information for transactional processing |
| Application - tracks information about an application (i.e., set of pages on a server) |
All objects take advantage of object-based programming to...
| Manage data "Collections" - input from browsers |
| Properties - states and attributes of the server, application , etc. |
| Methods - to get things done |
The Request object
The Request object is used to get information from the browser via the HTTP request. Collection includes...
| QueryString - get data from a URL request |
| Form - to get data from an HTML form |
| Cookies - get cookie data |
| ServerVariables - set and get HTTP information such as the server name |
The Response object
The Response object is used to send information to the user. Properties for the response object include:
| Buffer - stores data for sending until all processing is complete. |
| ContentType - to set the type of content (i.e: text/HTML, Excel, etc.) |
| Expires - sets the expiration of a web pages (in minutes). |
The following methods are supported by the Response object:
| AddHeader - adds HTML header with a specified value |
| AppendToLog - Appends a string to the end of the Web server log file |
| BinaryWrite - sends binary data (i.e, graphics, spreadsheet data) |
| Clear - clears buffered HTML output. |
| End - stops processing of the script. |
| Flush - sends all of the information in the buffer. |
| Redirect - redirect the user to a different URL |
| Write - to write into the HTML stream. This can be done by using the construct |
The Server object
The Server object supports one property, ScriptTimeout, which allows you to set the value for when the script processing will time out, and the following methods:
| CreateObject - create an instance of a server-based component. This component can be any component that you have installed on your server (such as an ActiveX ). |
| HTMLEncode - encode the specified string in HTML. |
| MapPath - map the current virtual path to a physical directory structure. |
| URLEncode - applies URL encoding to a specified string. |
The Session object
The Session object is used to store information about the current user's Web-server session. Variables stored with this object exist as long as the user's session is active, even if more than one application (script pages) is used. This object supports one method, Abandon, which abandons the current Web-server session and destroys all objects
Two properties:
| SessionID - the identifier for the current session |
| Timeout - specifies time-out value for the session. |
The Application object
The Application object can store information that persists for the entire lifetime of an application, that is, a group of pages with a common root.
Server Scripting - VBScript
| VBScript is a derivative of Visual Basic (same syntax, a subset of total VB environment) |
| Origins, uses, background, versions - review text |
| Data types, operators, evaluations, statements, structure - review text and examples |
| Creating and testing server scripts |
Environment for Running ASP...
| Personal Web Server (Win 95/98/NT WS) or IIS (Win NT/2000) |
| ASP is installed with the server |
| ASP scripts must be run in a virtual directory or location with scripting privileges turned on |
| There are tools for UNIX platforms to run ASP (ChiliSoft) |
Web Sites
| Microsoft ASP Site: http://msdn.microsoft.com/workshop/server/asp/ASPover.asp - tutorials, technology details |
| Charles Caroll's Site - http://activeserverpages.com/ - local developer/expert, site has many examples |
| Eric Smith's site - http://asptechniques.com |
| http://aspfree.com |