Calling scripts within scripts

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Overview

When writing an ASP script, it is sometimes useful to temporarily transfer execution to another script, and then continue the original script with the result of the called script.

This is what the AspRetrieve component does. You can think of it like calling a procedure.

The AspRetrieve component acts similar to the new function Server.Execute in IIS 5.0. In addition, you can pass parameters, either by GET or by POST.

The functionality of the AspRetrieve component in brief:

• call any URL from within an ASP script
• pass parameters to the URL either in the URL itself (i.e. by GET) or by POST
• retrieve the results form the called URL as a string

Because I only needed limited functionality, only textual results are correctly returned from the called URL. i.e. you can call a HTML page, or an ASP script, but you cannot call a GIF or JPEG image, since the latter two return binary data.

If you would like to extend the functionality, I would love to have this new version.

Details

The AspRetrieve component consists of two parts:

• A MFC/ATL component that uses the Wininet functions to call an URL
• Some ASP functions that aid in accessing the MFC component

In addition I included some examples

Installation

• Compile the MFC/ATL part of the component, using Visual C++ (I used the german version of Visual C++ 6, SP3)
• Copy the component to whatever directory you want it, ensuring the account under which IIS runs (IUSR_XXX) has the correct permissions to access the component
• Register the compiled component using regsvr32 (which is in your windows' system directory). Just type regsvr32 aspretrieve.dll at the command prompt
• Copy the ASP function file retrieve.inc to whatever directory you want
• Include retrieve.inc in your projects and begin using it

Usage

When everything is installed correctly, just include the retrieve.inc file in your ASP scripts and call the two functions Retrieve(url) and RetrievePost(url,params). You can either use relative URLs or absolute URLs for calling.

A practical use of the component is at those places, where you would need a lot of Response.Write statements to produce HTML output. Those functions can now be separated into extra ASP files, feeded with parameters and called via the AspRetrieve component.

Example

Imagine you have a function that creates a table by code. 

Without the AspRetrieve component, you would write something like this to implement the function:

sub makeTable( byval cols, byval rows )
	dim c,r

	Response.Write "<table border=""0"" width=""100%"">"

	' create rows.
	for r=1 to rows
		Response.Write "<tr>"

		' create cols.
		for c=1 to cols
			Response.Write "<td width=""100%""></td>"
		next

		Response.Write "</tr>"
	next

	Response.Write "</table>"
end sub

You call the function like this:

<% makeTable 10, 20 %>

When using the AspRetrieve, you implement the function in a separate ASP script like this:

<table border="1" width="100%">
	<%
	' create rows.
	dim c,r
	for r=1 to Request("rows")
	%>

		<tr>

			<%
			' create cols.
			for c=1 to Request("cols")
			%>
				<td width="100%"></td>
			<%
			next
			%>

		</tr>
	<%
	next
	%>
</table>

You could then write a wrapper to simplify calling:

sub makeTable( byval cols, byval rows )
	Response.Write Retrieve( "maketable.asp?cols="&cols&"&rows="&rows )
end sub

And finally you would call the wrapper in your code

<% makeTable 10, 20 %>

Conclusion

The advantages of using AspRetrieve are that you can divide a complex application into individual modules. You can create a library of ASP scripts that you can call as needed. 

In addition by cutting down the number of times you need to use Response.Write, you simplify your code. Having code in separate files, you can even use a graphical layout tool to modify your files, which is impossible if you construct your page with Response.Write.

Another benefit is that you no longer need to include all files "at compile-time" using the <!--#include--> directive, but can "include" these files dynamically at runtime using the Retrieve function! (a feature that e.g. JSP has by default).

Please feel free to ask any questions you have by e-mail: keim@zeta-software.de.