关于validation.xml的问题？

Question

validation.xml：
<form-validation>
    <formset>
        <constant>
            <constant-name>qqList</constant-name>
            <constant-value>/d{5,9}&/w{1,16}</constant-value>
        </constant>
        <form name="UpdateForm">
            <field
                property="qqList"
                depends="required,mask">
                <msg name="required" key="qqList.required"/>
                <msg name="mask" key="enter.qq.error"/>
                <var>
                    <var-name>mask</var-name>
                    <var-value>${qqList}</var-value>
                </var>
            </field>                                                                  
        </form>
    </formset>
</form-validation>
当这样写时报错：
HTTP Status 404 - Servlet action is not available
当把/d{5,9}&/w{1,16}中的&去掉后 就正确了，这是为什么呢？我要验证的是 5-9位数字然后是&然后是1-16位的字符 这应该怎么写呢？