PropertyEditor error

I have a custom tag in which I am evaluating an attribute as follow:

(Locale)ExpressionEvaluatorManager.evaluate("locale", expr, 
Locale.class, this, pageContext)

But I get an error:

javax.servlet.jsp.JspException: An error occurred while evaluating custom action attribute "locale" with value "en_US": Attempt to convert String "en_US" to type "java.util.Locale", but there is no PropertyEditor for that type (null)
	at org.apache.taglibs.standard.lang.jstl.Evaluator.evaluate(Unknown Source)
	at org.apache.taglibs.standard.lang.jstl.Evaluator.evaluate(Unknown Source)
	at org.apache.taglibs.standard.lang.support.ExpressionEvaluatorManager.evaluate(Unknown Source)


I am using standard.jar (v 1.1).

If I want to convert a String to Locale object, I assume I need to 
define some sort of PropertyEditor??

Any help is appreciated.

Thanks,

Mujahid