OnError in application.cfc

The error logged is variable is undefined. But I know, we have set the cfparam and default value as "". Not sure, if that was causing the problem, so I changed that to "0".

The error message suggests that the cfparam isn't in Coldfusion's memory when the error occurs. Trace the steps back, from where the error occurs to the cfparam tag.

I thought, onError will stop the application to run further, if any error found.

It will, if the error occurrs in one of Application.cfc's methods. Otherwise, it will work as Adam has described.

You should consider using the cferror tag, in place of onError. It might fit your requirements better. If you decide to do so, you should locate it in Application.cfc as in the following example:

<cfcomponent displayname="MyApp application file">
    <cfscript>
        this.name = "myApp";
        this.applicationTimeout = "#createTimespan(1,0,0,0)#";
        this.loginStorage = "session";
        this.sessionManagement = "true";
        this.sessionTimeout = "#createTimeSpan(0,0,20,0)#";
   </cfscript>
   <cferror exception="any" type="exception" template="relative_path_to_error_page.cfm">
<cffunction name="onApplicationStart" returntype="boolean">
    <cfreturn true>
</cffunction>

<cffunction name="onSessionStart">
</cffunction>
<!--- other events, etc., etc., excluding onError --->
</cfcomponent>

onError() does only what you tell it to do.  It does not automatically cause the app to halt... what if that's not how you want your errors to be handled?  The whole idea of the handler is that the default behaviour (output the exception details and stop processing) can be overriden with other - custom-written - behaviour.  So the handler makes no assumptions about what it should be doing.

If you want the thing to stop, either <cfabort> or rethrow the exception (depending on circumstance).

--

Adam