Here's a basic example of using the onError
function in application.cfc to log errors to an application-specific log file.
<cfcomponent output="false">
<cfset this.name = "myApp">
<cffunction name="onError">
<cfargument name="exception" required="true">
<cfargument name="eventName" type="string" required="true">
<cfset var myAppName = this.name>
<cfset var details = "">
<!--- You need to specify and check for the exception details you want to include in your log text --->
<cfif IsDefined( "exception.type" )>
<cfset details = "Type: #exception.type#. ">
</cfif>
<cfif IsDefined( "exception.message" )>
<cfset details = details & "Details: #exception.message#">
</cfif>
<cflog type="error" file="#myAppName#" text="#details#">
<!--- Specify how you want the error to be handled once it's been logged --->
<cfdump var="#exception#">
</cffunction>
</cfcomponent>
You need to specify which parts of the exception details you want to include in your log entry, bearing in mind that the keys of the exception struct will vary according to the type of error thrown. It's therefore best to check for their existence before adding them to the log text.
Official onError docs for ColdFusion MX7 (since your question's tagged with that version - which is also why I've used tags rather than cfscript in my example to be on the safe side).