How to export data with displaytag with custom Decorator

I have problem exporting data with the displaytag with the custom decorator.

I am using the displaytag and the custom Decorator. It work fine in the web display.

However, I used the export function excel and csv. the framework does not look up for the customer Decorator.?

Exception: [.LookupUtil] Error looking up property "mins" in object type "Productionorder". Cause: Unknown property 'mins'
	at org.displaytag.util.LookupUtil.getBeanProperty(LookupUtil.java:141)
	at org.displaytag.model.Column.getValue(Column.java:124)

The property "mins" is defined in the custom decorator.

I wonder how to fix it.

为什么不说中国话呢??