Global values as Tag parameters....How???

[Jonathan]

I am creating a custom Struts tag which needs to search for an object in a HashMap.  I want the 'key" for the object in the HashMap to be some agreed upon, pre-defined, final global value defined in a file available to the whole application.  How do I refer to this value in a Tag attribute?   eg. <html:userTargetedMessages messagesObjectKey="Globals.MESSAGES_OBJECT"/>   where "Globals.MESSAGES_OBJECT" is some static final variable in a file