Richfaces Tree and Seam EntityManager Problem

[grdzeli_kaci]

hi all,
i use seam and richfaces together, i have generated tree components from database, everything works fine i see tree components that containing information from database, but when i tried to expand tree component i got an error

Caused by: org.jboss.seam.RequiredException: In attribute requires non-null value: menu.entityManager

why get entitymanger null ??
here is my example:

@Name("menu")
@Scope(ScopeType.SESSION)
public class MenuBean{

 @In
 private EntityManager entityManager;

 private HtmlPanelBar bar = new HtmlPanelBar();
 public MenuBean() {
 }

 public HtmlPanelBar getBar() {
 if (bar!=null && bar.getChildren()!=null) {
 bar.getChildren().clear();
 }

 ArrayList<Menu> arraylist = (ArrayList<Menu>)entityManager.createNamedQuery("Menu.findAll").getResultList();
 for (Menu elem : arraylist) {
 HtmlPanelBarItem item= new HtmlPanelBarItem();
 item.setLabel(elem.getDescriptionId().getDescription());

 Library library = new Library(entityManager);

 HtmlTree tree = new HtmlTree();
 tree.setStyle("width:150px");
 tree.setValue(library.getData());
 tree.setVar("item");
 tree.setNodeFace(library.getType());

 Iterator<MenuGroup> iteratMenuGroups = elem.getMenuGroupCollection().iterator();
 while (iteratMenuGroups.hasNext()) {
 MenuGroup menuGroup = iteratMenuGroups.next();
 HtmlTreeNode treenodeMenuGroup = new HtmlTreeNode();
 treenodeMenuGroup.setType("menugroup");
 HtmlOutputText textMenuGroup = new HtmlOutputText();
 textMenuGroup.setTitle(menuGroup.getDescriptionId().getDescription());
 treenodeMenuGroup.getChildren().add(textMenuGroup);

 tree.getChildren().add(treenodeMenuGroup);
 }
 item.getChildren().add(tree);
 bar.getChildren().add(item);

 /*
 *Iterator<Article> iteratArticles = menuGroup.getArticleCollection().iterator();
 while (iteratArticles.hasNext()) {
 Article article = iteratArticles.next();
 HtmlTreeNode treenodeArticle = new HtmlTreeNode();
 treenodeArticle.setType("article");
 HtmlOutputText textArticle = new HtmlOutputText();
 textArticle.setTitle(article.getDesctiptionId().getDescription());
 treenodeArticle.getChildren().add(textArticle);
 }
 */
 }
 return bar;
 }
 public void setBar(HtmlPanelBar bar) {
 this.bar = bar;
 }
}

is this known issue ??
any idea will be appreciated,

____________________
Regards,
Paata.