在写时一定要加上:form 标签外加上<s:head theme=""/> 才可以;
eg:
<s:head theme=""/>
<s:form name="messageForm" method="post" theme="simple"
id="messageForm">
<div class="title">
数据比对差异报告
</div>
<div class="search" id="search">
<table class="table">
<tr>
<td width="4%" rowspan="3"><img src="${path}/page/wrm/image/search.gif" width="40" height="39"></td>
<td nowrap="nowrap">消息大类</td>
<td><s:select name="message.type" list="msgList" listKey="number" listValue="name" headerKey="" headerValue="--全部--" emptyOption="false" theme="simple" cssClass="select"/></td>
<td nowrap="nowrap">消息中类</td>
<td><s:select name="message.type" list="msgList" listKey="number" listValue="name" headerKey="" headerValue="--全部--" emptyOption="false" theme="simple" cssClass="select"/></td>
<td nowrap="nowrap">消息小类</td>
<td><s:select name="message.type" list="msgList" listKey="number" listValue="name" headerKey="" headerValue="--全部--" emptyOption="false" theme="simple" cssClass="select"/></td>
<td rowspan="3" align="center">
<input type='button' onclick="doQuery();" class="button" value="查 询" />
</td>
</tr>
<tr>
<td nowrap="nowrap">标题</td>
<td nowrap="nowrap">
<s:textfield name="message.title" cssClass="text" onchange="getTrimString(this)" />
</td>
<td nowrap="nowrap">所属区域</td>
<td nowrap="nowrap">
<s:textfield name="message.region" cssClass="text" onchange="getTrimString(this)" />
</td>
<td nowrap="nowrap">状态</td>
<td>
<select name="message.dealFlag" id="message.dealFlag" class="select">
<option value="">--全部--</option>
<option value="1">已处理</option>
<option value="0">未处理</option>
</select>
</td>
</tr>
<tr>
<td nowrap="nowrap">开始日期</td>
<td><s:datetimepicker name="startTime" theme="simple" displayFormat="yyyy-MM-dd" /></td>
<td nowrap="nowrap">结束日期</td>
<td><s:datetimepicker name="endTime" theme="simple" displayFormat="yyyy-MM-dd" /></td>
<td>
</td>
<td>
</td>
</tr>
</table>
</div>.............................<form>