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Application-level varibale?

Posted on 2002-05-19

1 solution

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Last Modified: 2012-05-04

I have controller.asp which parses a XML file. All http requests come to the controller.asp with a request type. (i.e All the forms' action attribute is equal to controller.asp in all pages with a hidden parameter for the request type). The controller.asp parses the XML file and based on the reqeuest type, gets a ASP Name from the XML file and transfers request to that ASP. This is the scenario.

In controller.asp, I am using the Microsoft XML DOM component to enable parsing. (Code Below). Since the XML DOM is created in the controller.asp, for every request, the DOM object is created, xml file loaded, parsed and destroyed, which is surely a performance overhead!

I am wondering if I can carry out the first two activities - (i.e Creating the XML DOM object and loading the XML file) once in the start of the application and just use this object in the controller.asp, then I am reducing the object creating and loading XML file overhead for the every request. right? Please let me know your opinions.

If right, I need some help with implementing it.

One way, is in the Application_OnStart eventhandler in global.asa file. I can create a application-level varibable set to the XML DOM object and load the XML file in the application-level variable. I can just use this application-level variable in the controller.asp to parse ! How is this implementation pattern? I have always heard and read that COM objects must not be put in Session. Considering this, can I put the XML DOM object (which is COM object) as a application level variable?

Seeking opinions!

******************************************************
<%

Dim requestType
Dim xmlDoc
dim NNPObj
dim docElement
dim nodeObj
dim docObj
dim childNode
dim rootNode
dim cNodes

requestType=request.form("requestType")

set xmlDoc=server.createobject("Microsoft.XMLDOM")
xmlDoc.async=false

dim bool

bool=xmlDoc.load(server.mappath("MyInfo.xml"))

set docElement=xmlDoc.documentElement
set cNodes= docElement.childNodes

for each nodeObj in cNodes
set NNPObj =nodeObj.attributes

if NNPObj.getNamedItem("id").nodeValue=requestType then
response.write "Request Type: "+ requestType +" <hr>"
response.write " Model Type: "+ NNPObj.getNamedItem("modelType").nodeValue +" "

if NNPObj.getNamedItem("modelType").nodeValue="asp" then

response.write " Processing ASP : "+ NNPObj.getNamedItem("ASPName").nodeValue +" <hr>"

elseif NNPObj.getNamedItem("modelType").nodeValue="com" then

response.write "Component Name: "+ NNPObj.getNamedItem("componentName").nodeValue +" "
response.write "Method Name :"+ NNPObj.getNamedItem("methodName").nodeValue +" "
response.write "Presentation Asp: "+ NNPObj.getNamedItem("presentationAsp").nodeValue +" <hr>"

end if
end if
Next

%>
*****************************************************
XMl File:

<controller>
<action id="getEmployee"
modelType="asp"
ASPName="getEmployee.asp"
/>
<action id="addEmployee"
modelType="asp"
ASPName="addEmployee.asp"
/>
<action id="generateOppurunity"
modelType="com"
componentName="SANGenSoft.Oppurunity"
methodName="generateOppurunity()"
presentationAsp="confirmOppurunity.asp"
/>
<action id="showOppurunity"
modelType="com"
componentName="SANGenSoft.Oppurunity"
methodName="showOppurunity()"
presentationAsp="showOppurunity.asp"
/>

</controller>
***************************************************

Comment

Question by:rajivraj

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11 Comments

LVL 23

Accepted Solution

by:b1xml2

b1xml2 earned 450 total points

ID: 70195112002-05-19

This is what you should do.

global.asa
===========
<object
id="oPersist"
progid="Microsoft.FreeThreadedXMLDom"
runat="server"
scope="application"></object>
<script language="VBScript" runat="server">

Sub Application_OnStart()
oPersist.async = False
oPersist.load Server.MapPath("MyInfo.xml")
End Sub

</script>

page.asp
========
<%

Dim oXML
'Setting it to the Application Scoped Variable
Set oXML = Application.StaticObjects("oPersist")

%>

LVL 23

Expert Comment

by:b1xml2

ID: 70195302002-05-19

Notes
=====
1. The way you are using XML and the DOM is not going to allow for an optimised performance-oriented outcome. In short, it is a clear abuse of the XML Process.

What will follow is the correct way of using XML to squeeze the most out of performance.

LVL 23

Expert Comment

by:b1xml2

ID: 70195382002-05-19

MSXML Parser That Should Be Used:
==================================
MSXML Version 3.0 SP 2 (Recommended MSXML Version 4.0)

controller.xsl
===============
<?xml version="1.0" encoding="iso-8859-1"?>
<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform" version="1.0">
<xsl:output method="html" indent="yes" encoding="iso-8859-1" />
<xsl:param name="requestType" />
<xsl:template match="/">
<xsl:apply-templates select="controller/action[@id [. = $requestType]]" />
</xsl:template>
<xsl:template match="action">
Request Type: <xsl:value-of select="@id" /> <hr />
<xsl:choose>
<xsl:when test="@modelType[ . = 'asp']">
<xsl:call-template name="asp" />
</xsl:when>
<xsl:when test="@modelType[ . = 'com']">
<xsl:call-template name="com" />
</xsl:when>
</xsl:choose>
</xsl:template>
<xsl:template name="asp">
Processing ASP: <xsl:value-of select="@ASPName" /> <hr />
</xsl:template>
<xsl:template name="com">
Component Name: <xsl:value-of select="@componentName" /> 
Method Name: <xsl:value-of select="@methodName" /> 
Presentation Asp: <xsl:value-of select="@presentationAsp" /> <hr />
</xsl:template>
</xsl:stylesheet>

global.asa
==========
<object id="oTemplate"
progid="Msxml2.XSLTemplate.3.0"
runat="server"
scope="application"></object>
<object id="oPersist"
progid="Msxml2.FreeThreadedDOMDocument.3.0"
runat="server"
scope="application"></object>
<script language="VBScript" runat="server">
Sub Application_OnStart()
Dim oXSLT
Set oXSLT = Server.CreateObject("Msxml2.FreeThreadedDOMDocument.3.0")
oXSLT.async = False
oXSLT.load Server.MapPath("controller.xsl")
Set oTemplate.stylesheet = oXSLT
Set oXSLT = Nothing
oPersist.async = False
oPersist.load Server.MapPath("controller.xml")
End Sub

</script>

page.asp
========
<%@language="VBScript"%>
<%
On Error Resume Next
Dim oTemplate, oProc, oPersist
Set oTemplate = Application.StaticObjects("oTemplate")
'get the IXSLProcessor whose rental model
'is suited for the application scope
Set oProc = oTemplate.createProcessor()
Set oPersist = Application.StaticObject("oPersist")
With oProc
.input = oPersist
.addParameter "requestType",Request("requestType")
.transform()

Response.Write(.output)
End With
Set oProc = Nothing
Set oPersist = Nothing
Set oTemplate = Nothing

%>

LVL 23

Expert Comment

by:b1xml2

ID: 70195442002-05-19

What's going on
===============
1. We can store the stylesheet in application scope directly using the Msxml2.FreeThreadedDOMDocument.3.0 progid but it is too heavy in resource management plus it is not designed for fast performance. How? If you have includes, it will not be loaded until at transform time, thus having a strong impact on transforms

2. Microsoft thus, created the IXSLTemplate and IXSLProcessor which is targetted especially in cases such as yours.

3. The problem with your code is that you will have to loop multiple times to do your work in your ASP Code. The XSLT Document takes care of that. More importantly, because of the rental model, it is lightweight. To create the IXSLProcessor, the following must be true.
The stylesheet used must be FreeThreaded. The IXSLTemplate's stylesheet property must be set to that of the FreeThreaded XSLT Document.

4. After getting the the IXSLProcessor, you can then set the input property to that of the Cached XML Document. This way will completely eliminate any I/O processes as every is taking place from memory.

5. By using the XML/XSLT Combination, the ASP code is leaner and meaner.

LVL 23

Expert Comment

by:b1xml2

ID: 70195632002-05-19

If you do not wish to change your code and want to use the older MSXML Parser, then you just change the global.asa and change the asp code to the following:
<%
Dim szRequestType
Dim oXML
Dim oNode
szRequestType = Request.Form("requestType")
Set oXML = Application.StaticObjects("oPersist")
Set oNode = oXML.selectSingleNode("/controller/action[@id[. = '" & szRequestType & "']]")
If Not oNode Is Nothing Then
Response.Write "Request Type: " & szRequestType & " <hr>"
Response.Write "Model Type: " & oNode.getAttribute("modelType") & " "
Select Case oNode.getAttribute("modelType")
Case "asp"
Response.Write "Processing ASP: " & oNode.getAttribute("ASPName") & " <hr>"
Case "com"
Response.Write "Component Name: " & oNode.getAttribute("componentName") & " "
Response.Write "Method Name: " & oNode.getAttribute("methodName") & " "
Response.Write "Presentation Asp: " & oNode.getAttribute("presentationAsp") & " <hr>"
End Select
Set oNode = Nothing
End If
Set oXML = Nothing
%>

LVL 23

Expert Comment

by:b1xml2

ID: 70195642002-05-19

by the way the amendment with regard to the controller.xsl, adding the model type display =)

<?xml version="1.0" encoding="iso-8859-1"?>
<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform" version="1.0">
<xsl:output method="html" indent="yes" encoding="iso-8859-1" />
<xsl:param name="requestType" />
<xsl:template match="/">
<xsl:apply-templates select="controller/action[@id [. = $requestType]]" />
</xsl:template>
<xsl:template match="action">
Request Type: <xsl:value-of select="@id" /> <hr />
Modal Type :<xsl:value-of select="@modelType" /> 
<xsl:choose>
<xsl:when test="@modelType[ . = 'asp']">
<xsl:call-template name="asp" />
</xsl:when>
<xsl:when test="@modelType[ . = 'com']">
<xsl:call-template name="com" />
</xsl:when>
</xsl:choose>
</xsl:template>
<xsl:template name="asp">
Processing ASP: <xsl:value-of select="@ASPName" /> <hr />
</xsl:template>
<xsl:template name="com">
Component Name: <xsl:value-of select="@componentName" /> 
Method Name: <xsl:value-of select="@methodName" /> 
Presentation Asp: <xsl:value-of select="@presentationAsp" /> <hr />
</xsl:template>
</xsl:stylesheet>

LVL 23

Expert Comment

by:b1xml2

ID: 70195692002-05-19

to download MSXML3 SP2, go to http://msdn.microsoft.com/xml and click on the right link MSXML3 SP2

if you wish to use MSXML4 SP1, click on the right link and read the install instructions. In the case of MSXML4, the version id should be changed from .3.0 to .4.0 in all cases presented here.

LVL 22

Expert Comment

by:CJ_S

ID: 70199122002-05-19

agrees with b1xml2. It IS the recommended way. although I personally hate the overload of the application. Especially if all xml output is save din the application scope, but that's just me :-/

CJ

LVL 23

Expert Comment

by:b1xml2

ID: 70221192002-05-20

rajivraj, feedback pls...

LVL 15

Expert Comment

by:gladxml

ID: 88364272003-07-01

No comment has been added lately and it seems that this question have been abandoned. So it's time to clean up this TA.

I will leave a recommendation in the Cleanup topic area that this question or invite a Moderator to close this question if there's no reply from you after seven days.

In the absence of responses, I will recommend the following:

To accept the comment and points awarded to b1xml2

** PLEASE DO NOT ACCEPT THIS COMMENT AS AN ANSWER **

Just trying to help for the cleanup...
gladxml

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