Creating dynamic tree in Seam with using recursiveTreeNodesAdaptor

I want to create dynamic tree in seam with using richfaces recursiveTreeNodesAdaptor.My entity classes is here ;

@Entity
public class Category extends Item implements Serializable {

private static final long serialVersionUID = -1154500438874768209L;
private List<Item> children;

public void addChild(Item child) {
    if (children == null)开发者_如何学编程 {
        children = new ArrayList<Item>();
    }

    if (!children.contains(child)) {
        children.add(child);
    }
}

@OneToMany(cascade = CascadeType.ALL)
public List<Item> getChildren() {
    return children;
}

public void setChildren(List<Item> children) {
    this.children = children;
}
}

 @Entity
 public class Product extends Item implements Serializable {  
    private static final long serialVersionUID = 3975153531436996378L;
 }

 @Inheritance(strategy = InheritanceType.JOINED)
 @Entity
 public class Item {
 private String name;
 private Long id;

 @Id
 @GeneratedValue
 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;
 }
}

and i use this class into here;

@Name("provider")
@Scope(ScopeType.APPLICATION)
public class OrganisationProvider implements Serializable {


private static final long serialVersionUID = 1L;

    public Category organization;

public OrganisationProvider() {
    if (organization == null) {
        setOrganization(createOrganization());

    }

}

public Category createOrganization() {
    Category ROOT = new Category();
    Category computerC = new Category();
    Category printerC = new Category();
    Category telephoneC = new Category();

    Product product = new Product();

    ROOT.setName("ROOT");
    computerC.setName("BilgisayarC");
    printerC.setName("YazıcılarC");
    telephoneC.setName("TelephoneC");

    computerC.addChild(printerC);

    ROOT.addChild(computerC);
    ROOT.addChild(product);

    return ROOT;
}

public void setOrganization(Category organization) {
    this.organization = organization;
}

public Category getOrganization() {
    return organization;
}
}

and my .xhtml page is ;

    <ui:define name="body">
    <h:form>
        <rich:panel id="dynamicTreePanel"
            header="Dynamic Tree User Interface">

            <rich:tree>
                <rich:recursiveTreeNodesAdaptor roots="#{provider.organization}"
                    var="rootOrg">
                    <rich:treeNode>
                        <h:outputText value="#{rootOrg.name}" />
                    </rich:treeNode>

                    <rich:recursiveTreeNodesAdaptor roots="#{rootOrg.children}"
                        var="childOrg" nodes="#{childOrg.children}">
                        <rich:treeNode>
                            <h:outputText value="#{childOrg.name}" />
                        </rich:treeNode>
                    </rich:recursiveTreeNodesAdaptor>

                </rich:recursiveTreeNodesAdaptor>
            </rich:tree>
        </rich:panel>
    </h:form>

</ui:define>

When the deploy page and click the root, I take this error;

javax.faces.FacesException: javax.el.PropertyNotFoundException: /dynamicItemTree.xhtml @23,52 nodes="#{childOrg.children}": The class 'a.b.c.d.Product' does not have the property 'children'.

The tree adaptor is reaching a Product item in one level and tries to read its children. This fails because there is no method getchildren on this class.

Either prevent calling getchildren in case its a Product or implement a method in Product that always returns null ( or empty array)