As most ColdFusion developers know, you cannot reference ‘application’ scoped variables directly in Application.cfc’s onSessionEnd() method. Instead you need to use the ApplicationScope parameter. Notes from the docs:
You must use the ApplicationScope parameter to access the Application scope. You cannot reference the Application scope directly; for example, use Arguments.ApplicationScope.myVariable, not Application.myVariable. Use a named lock when you reference variables in the Application scope, as shown in the example.
I ran into this today when working on some code a colleague wrote which was firing a method in an application scoped component, the code was as follows:
<cffunction name="onSessionEnd" output="false" returnType="void"> <cfargument name="SessionScope" required="true" /> <cfargument name="AppScope" required="true" /> <cfscript> arguments.AppScope.myCFC(arg=arguments.SessionScope.arg); </cfscript> </cffunction>
Obviously this method is being executed when the users session has expired. The use of arguments.AppScope means I can access the ‘myCFC’ component which is stored in application scope.
Now to the actual problem…inside the cfc was a method which was logging information in the database, but the datasource value was coming from application scope.
<cfquery datasource="#application.dsn#" name="qInsert">
Obviously arguments should be passed to components instead of being accessed directly, but that’s another story :)
I would have thought this would work fine, but no luck. It was a little bit of a pain to debug as you can’t see the results of onSessionEnd() being run.
The fix was simply to pass in the required variables as arguments to the method:
<cffunction name="onSessionEnd" output="false" returnType="void"> <cfargument name="SessionScope" required="true" /> <cfargument name="AppScope" required="true" /> <cfscript> arguments.AppScope.myCFC(arg=arguments.SessionScope.arg,dsn=arguments.Appscope.dsn); </cfscript> </cffunction>
Either way, be careful when doing this particularly if the method is being called from multiple application points and one of those could be onSessionEnd().