PrimeFaces p：commandButton不可拖动

Question

这是我的XHTML片段：

<h:form><p:separator/><p:panel header="Attachments" toggleable="true" disabled="false" readonly="false" rendered="true">
    <c:forEach id="availableAttachments" items="#{userCRBean.user.attachments}" var="attachment" varStatus="status">
        <p:commandButton ajax="false" disabled="false" id="attachmentButton" readonly="false" rendered="true" value="#{attachment.fileName}">
            <p:fileDownload value="#{userCRBean.handleFileDownload(attachment)}"/>
        </p:commandButton>
    </c:forEach>
    <p:draggable revert="true" for="attachmentButton" disabled="false" readonly="false" rendered="true"/>
    <p:droppable activeStyleClass="ui-state-highlight" tolerance="touch" for="fileUpload" disabled="false" readonly="false" rendered="true">
        <p:ajax listener="#{userCRBean.handleFileDelete(attachment)}" update="" disabled="false" readonly="false" rendered="true"/>
    </p:droppable>
    <p:fileUpload dragDropSupport="true" fileUploadListener="#{userCRBean.handleFileUpload}" id="fileUpload" mode="advanced" sizeLimit="1000000" update="@form"/>
</p:panel></h:form>

我想让c：forEach生成的p：commandButtons可拖动，但它们根本不会移动。任何想法，我在这里做错了什么？

PrimeFaces 5.2