<form name="fileForm" id="fileForm" action="${pageContext.request.contextPath}/Processes?action=upLoadImg&className=SearchUploadServlet" onsubmit="return check();" method="post" enctype="multipart/form-data" >
<table>
<c:if test="${uploadFileName !=null}">
<tr>
<td>
<img width='200px' title="" height='200px;' src="${pageContext.request.contextPath}/searchupload${uploadFileName }">
<p style="color:red;">${errorMessage }</p>
</td>
</tr>
</c:if>
<tr>
<td>
请选择上传的图片或文件:<input type="file" name="fileName" id="fileName" accept="image/jpeg,image/png,image/gif" onchange="return fnSubmit();"/>
</td>
</tr>
<tr>
<td>大类索引
<select id="maxSelect" style="width:200px" onchange="fnSelect(this.value)" >
<option selected="selected"></option>
<c:forEach var="largeIndexList" items="${largeIndexList}">
<c:if test="${maxSelectId==largeIndexList.indexName}">
<option value="${largeIndexList.indexName}" selected="selected">${largeIndexList.indexNameCn}</option>
</c:if>
<c:if test="${maxSelectId!=largeIndexList.indexName}">
<option value="${largeIndexList.indexName}">${largeIndexList.indexNameCn}</option>
</c:if>
</c:forEach>
</select>
<input type="hidden" id="selectId" name ="selectId">
</td>
<td>
<input type="button" value="搜索" onclick="subMit();"/>
<input type="hidden" id="uploadImg" name ="uploadImg" value="${uploadFileName }">
</td>
</tr>
</table>
</form>
后台servlet如何获得selectId的值