Primefaces

Question

我有一个问题，selectedArticleGroup总是 NULL !!!

这是我的课程：

                <p:selectOneMenu id="categorie_article"
                    value="#{articleGroupListController.selectedArticleGroup}"
                    effect="fade" converter="omnifaces.SelectItemsConverter"
                    filter="true" filterMatchMode="startsWith">
                    <f:selectItem itemLabel="Select One" noSelectionOption="true" />
                    <f:selectItems
                        value="#{articleGroupListController.articleListGroup}"
                        var="articleListGroup" itemLabel="#{articleListGroup.name}" itemValue="#{articleListGroup}"  />
                    <f:ajax render="selected_item" />
                </p:selectOneMenu>

豆子：

    @SessionScoped
    @Named
    public class ArticleGroupListController implements Serializable {
    ....
        private ArticleGroup selectedArticleGroup;
......GETTER + SETTER

转换器的实现在omnifaces jar中。

问题是：articleGroupListController.selectedArticleGroup总是为null。 请问有人帮帮我吗？