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CHAPTER 3
Extending Active Server Pages |
Chapter 1, Active Server Pages: An Introduction, presented a very brief overview of the Active Server Pages application paradigm. This chapter covers the various extensions for ASP. Some of these are included with IIS 4.0 and ASP 2.0, and some are available via the World Wide Web. Extending Active Server Pages applications usually takes the form of instantiating server-side objects that expose methods and properties that you can access through your server-side code. Microsoft includes many of these Active server components with IIS 4.0. For example, one of the server components included with IIS is the Browser Capabilities component. Once instantiated, a Browser Capabilities object allows you to discern details about the user’s web browser: what scripting it 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. As will be discussed in Chapter 8, Server Object, you use the CreateObject method of the Server object to instantiate a server component. For example, to create a MyInfo object in your Active Server Page, you could use code similar to the following: <% ' Declare local variables. Dim objMyInfo ' Instantiate a MyInfo object. Set objMyInfo = Server.CreateObject("MSWC.MyInfo") ' You can now initialize the values. objMyInfo.PersonalName = "A. Keyton Weissinger" ...[additional code] %> As you see in this example, instantiating these server components is simple. Once instantiated, you can use any of an object’s exposed methods or properties to extend your web application. Although IIS comes with several server components, you also can write your own in any development language that can create COM objects, such as Microsoft Visual Basic, Visual C++, Visual J++, or Inprise’s Delphi. The details of writing server components are beyond the scope of this book, so I would encourage you to read O’Reilly’s forthcoming Developing ASP Components, by Shelley Powers. The server components discussed in this book are described in Table 3-1. Table 3-1: Server Components Discussed in ASP in a Nutshell Server Component Description ADO Adds database access to Active Server Pages applications. Through its COM interface to OLE DB data providers, you are able to access any OLE DB or ODBC compliant data source. 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, mailenabled groupware applications using ASP. Although only introduced in this book, CDONTS is a powerful extension to ASP. Content Linking Maintains a linked list of static content files. From within these static files, the Content Linking component allows you to set up easy-to-use navigation from one page to the next (or previous) 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 Ad Rotator 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 anywhere 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 webmaster’s name, address, company, etc., from within your web applications. 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 on the network. This allows you to determine on the fly whether the current user has permission to see a file. PART II Object Reference This part covers every aspect of the intrinsic objects that make up the IIS object model. This includes every event, method, property, and collection for the Application, ObjectContext, Request, Response, Session, and Server objects. This part also includes a reference for all of the ASP directives and in-depth coverage of the GLOBAL.ASA file. Because support for these objects, as well as for the GLOBAL.ASA file, is built in to Active Server Pages, you can access and take advantage of all of these components from ASP automatically; no additional components or libraries are needed. Part II is organized into the following chapters: Chapter 4, Application Object Chapter 5, ObjectContext Object Chapter 6, Request Object Chapter 7, Response Object Chapter 8, Server Object Chapter 9, Session Object Chapter 10, Preprocessing Directives, Server-Side Includes, and GLOBAL.ASA |