public class XPDSerializer extends XStreamSerializer{
public static void main(String args[]) throws Exception{
ArrayList list = new ArrayList();
ActivityTypeDescriptor descr = new ActivityTypeDescriptor();
descr.setActivityTypeClass("org.uengine.kernel");
descr.setGroup("name");
list.add(descr);
list.add(descr);
XPDSerializer xpdSer = new XPDSerializer();
xpdSer.serialize(list, System.out, null);