Trying TreeModel for GrailsZK plugin

Menu.groovy

class MenuModel extends AbstractTreeModel<Menu> implements TreeSelectableModel {

  public MenuModel(Menu root) {
		super(root)
	}
	
	@Override
	public Menu getChild(Menu menu, int index) {
		return menu.getAt(index);
	}

	@Override
	public int getChildCount(Menu menu) {
		return menu.getChildCount();
	}

	@Override
	public boolean isLeaf(Menu menu) {
		return menu.isLeaf();
	}

}

class MenuComposer extends zk.grails.Composer {

  private MenuModel menu
	
    def afterCompose = { window ->
    }
	
	public MenuModel getMenuModel() {
		println "menu requested..."
		Menu menuRoot = new Menu()
		menuRoot.descr = 'Cadastros'
		
		Menu tabelasBasicas = new Menu()
		tabelasBasicas.descr = 'Tabelas Básicas'
		
		Menu empresasPessoas = new Menu()
		empresasPessoas.descr = 'Empresas e Pessoas'
		
		Menu as0013 = new Menu()
		as0013.descr = 'Consulta Agenda e Cadastro'
		as0013.codPrograma = 'AS0013'
		
		empresasPessoas.addChild(as0013)
		tabelasBasicas.addChild(empresasPessoas)
		menuRoot.addChild(tabelasBasicas)
		
		menu = new MenuModel(menuRoot)
		return menu
	}
	
}

<?xml version="1.0" encoding="UTF-8"?>
<?variable-resolver class="org.zkoss.zkplus.spring.DelegatingVariableResolver"?>

<zk xmlns="http://www.zkoss.org/2005/zul"
    xmlns:h="http://www.w3.org/1999/xhtml"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://www.zkoss.org/2005/zul http://www.zkoss.org/2005/zul/zul.xsd">

    <window id="menuWindow" apply="br.com.insoft4.zk.MenuComposer">

        <tree id="menuTree" width="100%" model="#{menuWindow$composer.menuModel}">
                  	
        </tree>

    </window>

</zk>