code: public static void addActionError( ServletRequest request, String propertyName, String messageKey )
      {
          InternalUtils.addActionError( propertyName, new ActionMessage( messageKey, null ), request );
      }
docs: Add a property-related message that will be shown with the Errors and Error tags.
  
  @param request the current ServletRequest.
  @param propertyName the name of the property with which to associate this error.
  @param messageKey the message-resources key for the message.