A brief meditation on encapsulation in ColdFusion

DataAccessObject.cfc

<!---
encapsulation is good stuff https://en.wikipedia.org/wiki/Encapsulation_(computer_programming)
--->

<cfcomponent>

  <cfset variables.dsn = '' />

  <cffunction name="init">
    <cfargument name="dsn" type="string" required="true" />
    <cfset variables.dsn = arguments.dsn />
    <cfreturn this />
  </cffunction>

  <cffunction name="sad_stuff">
    <!--- referring to the request scope inside of a cfc breaks encapsulation --->
    <cfquery name="aQuery" datasource="#request.dsn#">
      ...
  </cffunction>

  <cffunction name="good_stuff">
    <!--- getting the datasource name from the object's properties respects encapsulation --->
    <cfquery name="aQuery" datasource="#variables.dsn#">
      ...
  </cffunction>

  <cffunction name="also_good_stuff">
    <!--- getting the datasource name from the arguments scope also respects encapsulation, but is less efficient --->
    <cfargument name="dsn" type="string" required="true" />
    <cfquery name="aQuery" datasource="#arguments.dsn#">
      ...
  </cffunction>

</cfcomponent>