hierarchical Tree Component filled via HbnContainer and Hibernate does not

Hi,I am having a hierachical tree compnent, whihc gets filled by a HbnController via Hibernate
When I try to expand a tree, by clicking on it, it will not work
Here is my code:

public class TreetestUI extends UI {
    @WebServlet(value = "/*", asyncSupported = true)
    @VaadinServletConfiguration(productionMode = false, ui = TreetestUI.class)
    public static class Servlet extends VaadinServlet {
    }
    private Tree myTree;
    private final static DatabaseUtil dbUtil = new DatabaseUtil();
@Override
    protected void init(VaadinRequest request) {
        final VerticalLayout layout = new VerticalLayout();
        layout.setMargin(true);
        setContent(layout);
        Button button = new Button("Click Me");
        button.addClickListener(new Button.ClickListener() {
            public void buttonClick(ClickEvent event) {
                layout.addComponent(new Label("Thank you for clicking"));
            }
        });
        myTree = new Tree();
        HbnContainer<MenuTree> container = new HbnContainer<MenuTree>(MenuTree.class, DatabaseUtil.getSessionFactory());
        myTree.setContainerDataSource(container);
        myTree.setItemCaptionPropertyId("name");
        layout.addComponent(myTree);
        layout.addComponent(button);
    }
}

Here is my PoJo

[code]
package com.example.treetest;
import java.io.Serializable;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.ManyToOne;
@Entity
public class MenuTree implements Serializable{
/**
*
*/
private static final long serialVersionUID = 290355216786167669L;
public Long getId() {
return id;
}
public void setId(Long id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public MenuTree getParent() {
return parent;
}
public void setParent(MenuTree parent) {
this.parent = parent;
}
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
private Long id;

    private String  name;

    @ManyToOne
    private MenuTree parent;

}
[/code]And attached is the data in the MenuTree Table

Any help is appricated
18012.png

when I add the following code, then I can expand and collapse

      for (Object itemId: menuTree.getItemIds())
      {
          myTree.expandItem(itemId);
      }