struts2中,jsp页面设置theme="ajax"

<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<%@ taglib prefix="s" uri="/struts-tags" %>
<%@ taglib prefix="sx" uri="/struts-dojo-tags" %>

<head>
    <title>tree.jsp</title> 
    <sx:head />

</head>

<body>
    <h3>
        tree和treenode标签使用范例
    </h3>
    <p>

        <sx:tree id="root" label="HTML">
            <sx:treenode label="<b>html1</b>" id="html1">
                <sx:treenode label="subhtml1" id="subhtml1"></sx:treenode>
                <sx:treenode label="subhtml2" id="subhtml2"></sx:treenode>
            </sx:treenode>
            <sx:treenode label="<b>html2</b>" id="html2" />
        </sx:tree>

    </p>
</body>

早期的sturts2中有s:tree,s:treenode等标签,新的struts2移到dojo里面了,但是sx:tree和sx:treenode都没有theme这个属性了,在这个jsp里面怎么设置theme="ajax"啊,sx:head也没有theme这个属性。