<rich：listshuttle> targetValue始终为空</rich：listshuttle>

Question

我有一个丰富的listShuttle（richfaces 3.3）：

<rich:listShuttle sourceValue="#{olapBackingBean.memberList}" 
                targetValue="#{olapBackingBean.selectedMemberList}" var="items"
                listsHeight="150" sourceListWidth="130" targetListWidth="130"
                sourceCaptionLabel="Members list"
                targetCaptionLabel="Selected Member">
                <rich:column>
                    <h:outputText value="#{items}"></h:outputText>
                </rich:column>
                <a4j:support event="onlistchanged"  />
                <a4j:support event="onorderchanged" />
</rich:listShuttle>

我的目标值列表始终为空，这是我的backingBean：

public void setSelectedMemberList(List<String> selectedMemberList) {
        this.selectedMemberList = selectedMemberList;

}
public List<String> getSelectedMemberList() {
        return selectedMemberList;

}

public void setMemberList(List<String> memberList) {
    this.memberList = memberList;
}
public List<String> getMemberList() {
    return memberList;
}

我的listShuttle位于modalPanel内。