XML ISAPI Filter
The purpose of this ISAPI filter is to be able to serve up Extensible Stylesheet Language (XSL) styled documents for browser clients that do not natively support XSL formatting (including versions of Internet Explorer prior to Internet Explorer 5.0). The filter also provides caching of the XSL style sheets in memory for improved performance on the server.
The filter is an MFC ISAPI Wizard-based application that also serves as a good sample application for those wanting to build their own custom XML ISAPI filters.
Installation
- Copy the
xmlisapi.zip file to your machine. - Extract the xmlisapi.dll. You can put it in the %SystemRoot%\SYSTEM32\INETSRV directory if you want - but it doesn't have to go there.
- From the Internet Service Manager console open the properties dialog for the Default Web Site
- Select the Home Directory tab
- Click the Configuration... button
- Add a new Application Mapping with the the xmlisapi.dll as the executable, the extension ".xml" and with the method exclusions PUT,POST,DELETE.
- Deselect the Script engine check box.
- Change the Permissions on the Home Directory from Script to Execute so the ISAPI filter is allowed to execute over on XML document in your website.
- The next GET request for a .xml document on your website will go through the ISAPI filter.
Usage
The XML ISAPI filter checks the client browser type. If it finds anything other than MSIE 5.x it will perform the XSL transform on the server.
If the ISAPI filter decides to do server side processing it loads the first 4096 bytes of the XML file and sniffs for the first <?xml:stylesheet or <?xml-stylesheet tag. (Note: If this PI does not specify text/xsl then it will not do server side processing - in other words, server-side CSS is not supported).
The ISAPI filter looks for either the href attribute of a new extended attribute in called server-href. If this is present it uses the stylesheet pointed to by that attribute for the server-side XSL processing. This allows you to have custom stylesheets for those clients that do not support client side XSL. For example:
<?xml-stylesheet type="text/xsl" href="advanced.xsl" server-href="ie4.xsl"?>
Source Code
The ISAPI filter was generated by the MFC ISAPI Wizard and so the following files marked with an asterix(*) are boiler plate files straight from that wizard:|
Filename |
Purpose |
|
Resource.h(*) |
Define constances used in resource files |
|
StdAfx.cpp(*) |
Standard include files. |
|
StdAfx.h(*) |
Standard include files - used to build precompiled headers. |
|
xmlisapi.cpp |
The real meat of the program. |
|
xmlisapi.def(*) |
Defines DLL entry points required by ISAPI filters. |
|
xmlisapi.dsp(*) |
The Visual C++ 6.0 project file for building the DLL |
|
xmlisapi.h |
Declares the classes that make up this application (CXslCache, CXmlHttpStream, and CXmlIsapiExtension. |
|
xmlisapi.rc(*) |
Resources - mostly just version information |
|
xmlisapi.rc2(*) |
More resource - this is basically empty boiler plate. |