引入AJAX后在fireFox中出现this.element is null

struts2 在引入AJAX后在fireFox中出现this.element is null 的错误提示,很可能的原因是textfield 和hidden 只定义了Name 而没有定义ID,

<s:textfield name="c_bsortCode"  cssClass="input-throbber"/>
                                    <s:hidden name="carInsPolicy.bsortCode">
                                    <span id="indicator_bsortCode" style="display:none;">
                                         <img src="<%=path%>/images/indicator.gif" />
                                    </span>
                                    <ajax:autocomplete
                                         source="c_bsortCode"
                                         target="carInsPolicy.bsortCode"
                                         baseUrl="${pageContext.request.contextPath}/codeAutocomplete.view?tableName=CbusinesssSort&source=c_bsortCode"
                                         className="autocomplete" 
                                         indicator="indicator_bsortCode" 
                                         minimumCharacters="0"/>

加了ID以后该问题则不存在了

<s:textfield name="c_bsortCode" id="c_bsortCode" cssClass="input-throbber"/>
                                    <s:hidden name="carInsPolicy.bsortCode" id="carInsPolicy.bsortCode"/>
                                    <span id="indicator_bsortCode" style="display:none;">
                                         <img src="<%=path%>/images/indicator.gif" />
                                    </span>
                                    <ajax:autocomplete
                                         source="c_bsortCode"
                                         target="carInsPolicy.bsortCode"
                                         baseUrl="${pageContext.request.contextPath}/codeAutocomplete.view?tableName=CbusinesssSort&source=c_bsortCode"
                                         className="autocomplete" 
                                         indicator="indicator_bsortCode" 
                                         minimumCharacters="0"/>

可能是这里的AJAX也是根据document.getElementId("")来取得相应的对象的