Primefaces 中的自动完成功能

我正在尝试实现自动完成。xhtml 文件中的代码：

<h:form>
    <p:panelGrid cellpadding="5" columns="2">
        <p:outputLabel value="Login:" for="name"/>
        <p:autoComplete id="name" value="#{autoBean.user}" completeMethod="#{uB.completeUser}" var="user"
                        itemLabel="#{user.login}" itemValue="#{user}" converter="userConverter" dropdown="true" forceSelection="true"/>

        <p:commandButton actionListener="#{autoBean.aList}">
            <f:ajax execute="name" render="out"/>
        </p:commandButton>
        <p:outputLabel id="out" value="#{autoBean.user.login}"/>
    </p:panelGrid>
</h:form>

Bean中的代码：

@ManagedBean(name="aB", eager = true)
@SessionScoped
public class AutoBean implements Serializable{
    private User user;
    private Locale locale;
    private List<User> users;

    @PostConstruct
    void init() {
        user = new User();
        DAOImpl dao = new DAOImpl();
        users = dao.getAllUsers();
        locale = new Locale("ru");
    }

    public List<User> completeUser(String query) {

        List<User> filteredUsers = new ArrayList<>();

        for (User user : users) {
            if (user.getLogin().toLowerCase().startsWith(query)) {
                filteredUsers.add(user);
            }
        }

        // Сортировка пользователей в автодополнении
        filteredUsers.sort(new Comparator<User>() {
            public int compare(User s1, User s2) {
                return s1.getLogin().compareToIgnoreCase(s2.getLogin());
            }
        });

    // Getters & Setters
}

类UserConverter：

@FacesConverter("userConverter")
public class UserConverter implements Converter {    

    public Object getAsObject(FacesContext fc, UIComponent uic, String value) {
        if(value != null && value.trim().length() > 0) {
            try {
                AutoBean autoBean = (AutoBean) fc.getExternalContext().getApplicationMap().get("aB"); // NullPointerException
                return autoBean.getUsers().get(Integer.parseInt(value));
            } catch(NumberFormatException e) {
                throw new ConverterException(new FacesMessage(FacesMessage.SEVERITY_ERROR, "Conversion Error", "Not a valid theme."));
            }
        }
        else {
            return null;
        }
    }   

    @Override
    public String getAsString(FacesContext arg0, UIComponent arg1, Object obj) {
        if(obj != null) {
            return String.valueOf(((User) obj).getLogin());
        }
        else {
            return null;
        }
    }
}

我NullPointerException上线

AutoBean autoBean = (AutoBean) fc.getExternalContext().getApplicationMap().get("aB");

在调试器中 - autoBean = null. 我查看了所有文档，但找不到原因。自动完成本身有效，用户列表可见，单击按钮时发生错误。