JavaServer Faces中的Ajax

I’m trying to use ajax in jsf. So, I have inputtextarea and datatable:

<h:form>
    <h:inputTextarea id="mailstextarea" style="width:100%" value="#{newMembersBean.newMembersStr}">
        <f:ajax event="keyup" render="newmembertable" execute="mailstextarea" />
    </h:inputTextarea>

    <h:dataTable id="newmembertable" styleClass="tableWidth" value="#{newMembersBean.newMembers}" var="member">
        <h:column>
            <f:facet name="header">#{msgs.name}</f:facet>
            #{member.name}
        </h:column>
        <h:column>
            <f:facet name="header">#{msgs.surename}</f:facet>
            #{member.sureName}
        </h:column>
        <h:column>
            <f:facet name="header">#{msgs.email}</f:facet>
            #{member.email}
        </h:column>
        <h:column>
            <f:facet name="header">#{msgs.phone}</f:facet>
            #{member.phone}
        </h:column>
    </h:dataTable>
    <h:commandButton type="submit" value="#{msgs.add}"/>
</h:form>

I want to change newMembersBean.newMembers List (and datatable newmembertable) on every value change in textarea… In my bean I’m trying to do somethink like this (now only for testing, I want to show all users, if user have typed more then 3 characters):

@Named
@ConversationScoped
public class NewMembersBean implements Serializable {
    private List<UsersEntity> newMembers = new ArrayList<UsersEntity>();
    private String newMembersStr = "";
    ......
    public List<UsersEntity> getNewMembers() {
        UsersDao ud = new UsersDao();
        if(newMembersStr.length() > 3)
        {
            newMembers = ud.getAllUsers();
        }
        return newMembers;
    }
   .....
}

But when I’m typing text in textare nothing happens. Please help. Thanks.