code: public MapKeyJoinColumn<ElementCollection<T>> getOrCreateMapKeyJoinColumn()
     {
        List<Node> nodeList = childNode.get("map-key-join-column");
        if (nodeList != null &&  nodeList.size() > 0)
        {
           return new MapKeyJoinColumnImpl<ElementCollection<T>>(this, "map-key-join-column", childNode, nodeList.get(0));
        }
        return createMapKeyJoinColumn();
     }
docs: If not already created, a new <code>map-key-join-column</code> element will be created and returned.
  Otherwise, the first existing <code>map-key-join-column</code> element will be returned.
  @return the instance defined for the element <code>map-key-join-column</code>