If you're defining this property in a DynaActionForm, specify initial="{}" when you define it in the struts-config.xml file. If you're writing your own ActionForm, overrride the reset(...) method and specify
somewhere in that method. Once you've done this, you can simply use the standard "required" validation for this property.
The reason you need to initialize it as an empty
String array is that if no checkbox is checked, nothing will get set to the server, and the validation framework doesn't recognize it.
[ November 25, 2007: Message edited by: Merrill Higginson ]