Why is a ColdFusion SESSION variable "undefined" after being referenced a few lines before?
coldfusion, coldfusion-8, session
Solution
It's most likely a thread safety issue with something else in your code clearing out session scope or assigning NULL to `SESSION.User`.
I suggest that because you don't seem to have a local declaration for `i` in your loop, so that code is not thread safe - and so you may have similar errors elsewhere in your code.
Problem
Running ColdFusion 8.01 Standard on Windows2003/IIS6 Application.cfc: ``` <cfcomponent output="false"> <cfscript> THIS.SessionManagement = "Yes"; THIS.SessionTimeout = CreateTimeSpan(0, 3, 0, 0); THIS.ApplicationTimeout = CreateTimeSpan(0, 8, 0, 0); </cfscript> <cffunction name="onRequestStart" returnType="Boolean" output="false"> <cfargument name="targetPage" type="string" required="true"> <cfscript> if (!StructKeyExists(SESSION, "User")) SESSION.User = CreateObject("component", "cfc.User"); </cfscript> </cffunction> </cfcomponent> ``` Template file Pseudo-Code Sample: ``` LOCAL.qItems = CreateObject( "component", "cfc.Items" ).setUser(SESSION.User).getItems(); for (i=1; i<=LOCAL.qItems.RECORDCOUNT; i++) { LOCAL.Item = CreateObject( "component", "cfc.Item" ).setUser( SESSION.User ).setId(LOCAL.qItems["Sku"][i]); } ``` SESSION.User is set (if not already defined) in `onRequestStart()` of `Application.cfc`. The above code runs in a template file. The second reference to `SESSION.User` has thrown an exception with the message `Element USER is undefined in SESSION`. Why would SESSION.User be defined (doesn't throw an exception) a few lines before, and then throw this exception a few lines later (within milliseconds)? This happens maybe once a day in different templates throughout my application. How can I prevent this?