jsp表单提交问题。。

Question

Hhadvertisement-add.jsp:
 <input id="advId" name="advId" type="hidden"  value="${obj}" >
        <table style="width: 600px;" cellpadding="0" cellspacing="1" class="formtable">
                <tr>
                    <td align="right">
                        <label class="Validform_label">
                            题目:
                        </label>
                    </td>
Hhadvertisement-update.jsp:
<t:formvalid formid="formobj" dialog="true" usePlugin="password" layout="table" action="hhAdvertisementController.do?doUpdate" tiptype="1"  callback="@Override uploadFile">
    
            <input id="id" name="id" type="text" value="${hhAdvertisementPage.id }"> 
            <input id="advId" name="advId"  type="hidden"  type="hidden"  value="${hhAdvertisementPage.id }" >
    
        <table style="width: 600px;" cellpadding="0" cellspacing="1" class="formtable">
        <tr>
                        <td align="right">
                            <label class="Validform_label">
                                题目:
                            </label>
                        </td>

这是添加和编辑jsp页面， 添加<input id="advId" name="advId" type="hidden" value="${obj}" >
和编辑
<input id="id" name="id" type="text" value="${hhAdvertisementPage.id }">

            <input id="advId" name="advId"  type="hidden"  type="hidden"  value="${hhAdvertisementPage.id }" >

隐藏提交的ID有啥用啊 id 和 advid