These methods serialize the access to application-level variables so that only one client at a time can read or modify the values. The following example shows how to use the Lock and Unlock methods to increment a user-counter variable whenever a user accesses the application.
By adding debug code to your application at design time, when you run into application object problems, you can make ASP list all the objects you have created with an application scope. The following code illustrates creating debug code for both the Contents and StaticObjects collections. You can see the code output in Figure on the following page. As you can see, objects and variables both can have an application scope.
It holds the variables for individual users across the web pages in your application. When you place a variable in the Session object, that variable is valid only for the current user and cannot be shared across users in the same way that an Application variable can. You can also create session variables in the same way you create Application variables, by using the syntax Session "VariableName".
The LCID property stores a standard international abbreviation that uniquely identifies a system-defined locale. The SessionID property returns to you the unique session identifier for the current user. You should remember, however, that this ID is unique only during the lifetime of the ASP application. If you restart your web server and therefore restart your web applications, the web server might generate the same IDs it already generated for the users before the web application was restarted. For this reason, you should avoid storing these IDs and attempting to use them to uniquely identify a user of your application.
The fourth property of the Session object is the Timeout property.
This property enables you to change the timeout period associated with a particular ASP session. Remember that by default, the timeout is set to 20 minutes.
If you know that your application will be used for less than 20 minutes, you might want to decrease the duration of the timeout so that sessions end more quickly and resources are returned to the web server at a faster rate. The only method of the Session object is the Abandon method. If the user attempts to reconnect to the web application, a new session starts on the server. Request Object The Request object allows you to access the information that was passed from the web browser to your web application.
The Request object is crucial in ASP applications since it enables you to access user input for your server-side scripts. For example, suppose a user fills out an HTML form that you created.
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Once the user clicks the Submit button on the form, the Request object contains the form information that was passed to the server. To understand when to use these collections, you first need to know about the different ways information can be passed from the web browser to the web server. Normally in your web applications, you use HTML forms to gather input from the user so that you can use it in your calculations or store it in a data source. The getinfo. Once the file determines which method was used, it displays the correct information for that particular type of form.
Figure shows a sample of the GET method. Figure When a user types an e-mail address and submits the form, the GET method is used to pass the information to the Request object. For a complete list of server variables, please see the IIS documentation. When using the QueryString collection, follow this format to retrieve the information: Request.
Instead, consider using the POST method. Instead, you need to use the Forms collection of the Request object. In the preceding example, the line Request. Form "firstname" retrieves the information the user typed into the First Name text box on the form. You can use this same syntax in your applications to retrieve information from an HTML form. Response Object The Response object is used to control the content that is returned to the client. For example, when you calculate a value on the server, you need a way to tell the ASP engine that you want to send the information back to the client.
You do this by using the Write method of the Response object. The Write method of the Response object will be the most commonly used method in your ASP applications. Even though you have not seen any explicit Response. Write statements in the examples, they are there. The shorthand version makes it easier for you to put these statements in your code quickly.
The Response object has a number of other collections, properties, and methods that you can use, such as the Expires property, which tells the web browser how long to cache a particular page before it expires. This is useful if you want to hold back the output of your ASP code until the script completes its processing. The best example for using buffering is to capture errors in your code.
For example, by turning buffering on using the command Response. If one has, you can clear the buffer without sending it by using the Response.
Clear method, and then you can replace the output with new output such as Response. Write "An error has occurred. Please contact the administrator. End method, which sends the new buffer to the client and stops processing any further scripts in the ASP. Server Object The Server object provides you with utility methods and properties to modify the information on your web server. The CreateObject method allows you to create an object on the web server by passing in the ProgID for the object.
Session" ASP creates an object and passes that object to you in the oSession variable. By default, when you do this on an ASP page, the object has page-level scope.
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This means that when ASP is done processing the current page, the object is destroyed. The one issue to watch out for with the CreateObject method and some objects is potential performance loss. You can instantiate almost every object on your web server as an ASP object, but some objects are specifically designed to run in a server-based, multiuser environment such as CDO.
When you instantiate an object that was not designed for an ASP environment, the application performance might suffer if many people hit the page containing that object at the same time. The ScriptTimeout property of the Server object allows you to specify how long a script should run before it is terminated. By default, an ASP script can run for 90 seconds before it is terminated, but this might not be enough time to retrieve data from a data source.
By using the following syntax for this property, you can increase or decrease the amount of time the script will run before termination: Server. You can also write your own components using any COM-based development tool. If you want to learn more about these components, you should refer to the documentation that ships with IIS version 4.
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This ASP application allows you to access your mailbox, calendar, and contacts as well as directory information using any standard web client. IIS 4.
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You can download the Window NT 4. You can install Outlook Web Access on the same server as your Exchange Server or on a separate server. The architecture for your web servers and Exchange Servers can vary depending on the topology of your network environment and requirements of your applications. For example, if few users will be accessing Outlook Web Access but you have a number of Exchange Servers and you do not want to set up multiple Outlook Web Access servers for each Exchange Server, you can set up just one Outlook Web Access server to talk to multiple Exchange Servers.
The opposite is true as well. Think of it as a web farm of Outlook Web Access servers. This will work as long as you make sure that when a user starts a session with an Outlook Web Access server in a web farm, that user stays with the same Outlook Web Access server until her session expires or she logs out. If the Exchange Server welcome screen does not start automatically, launch it by double-clicking on Launch.
Click on Server Setup And Components. Click on Microsoft Exchange Server 5. The setup program will prompt you for the name of an Exchange Server that Outlook Web Access should connect to. Type a name of a server that contains an entire replica of the Exchange Server directory. This sets up Outlook Web Access so that it automatically redirects itself to the Exchange Server where the mailbox of the user resides. It also allows you to set up one Outlook Web Access web server that talks to multiple Exchange Servers. This service pack includes a number of enhancements for the Outlook Web Access client, such as the ability to access Outlook contacts from the Web.
After running the update, you need to set the proper permissions in the User Manager For Domains.
From the displayed page, you can log in as an Exchange user or log in with anonymous access. Anonymous access is discussed in more detail in Chapter Figure shows how Outlook Web Access looks when you log on as an Exchange user.