The purpose of the NonNullLinkedHashMap is so we keep the ordering of elements and also to avoid nulls getting the metadata. If you just use a normal HashMap you loose the ordering (which maybe important in some places!) If XMLElement.type is the wrong place to define the implementation class then we should define our own annotation. View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=4090930#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...