servlet端：

for (int i = 0; i < smart.getFiles().getCount(); i++) {
SmartFile files = smart.getFiles().getFile(i);
//System.out.println(files.getFileName());
if (!files.isMissing()) {
SimpleDateFormat sdf = new SimpleDateFormat(
"yyyyMMddHHmmssSSS");
String name = sdf.format(new java.util.Date());
name = name + "." + files.getFileExt();// 得到文件的扩展名
String filename = this.getServletContext().getRealPath("/")
+ "images\\" + name;
smart.getFiles().getFile(0).saveAs(filename);
}

jsp端：

function onupchg(_v) {
myhtml = "";
for (var i = 0; i < _v; i++) {
myhtml += "<input style='height:25px; margin-bottom:6px;' class='txt1' type='file' name='user_upload_file' />";
}
alert(myhtml);
document.getElementById("uparea").innerHTML = myhtml;
}

<form method="post" action="addgoods.do" enctype="multipart/form-data">

上传图片：
<select size="1"
onchange="onupchg(this.options[this.selectedIndex].value)"
name="upfile" style="margin: 2px; font-size: 12px;">
<option selected="selected" value="1">
1张
</option>
<option value="2">
2张
</option>
<option value="3">
3张
</option>
<option value="4">
4张
</option>
<option value="5">
5张
</option>
</select>

</td>
<td style="text-align: left; padding: 5px; font-size: 12px;"
id="uparea" valign="top">
<input class="txt1" name="user_upload_file" type="file">
</td>

</form>