JSP文件路径传到servlet出现中文乱码怎么办

jsp
===============================================
<%@ page language="java" import="java.util.*" pageEncoding="utf-8"%>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<script type="text/javascript">


var xmlHttp;
function createXmlHttp(){
if(window.ActiveXObject){
return new ActiveXObject("Microsoft.XMLHTTP");
}
if(window.XMLHttpRequest){
return new XMLHttpRequest();
}
}
function upLoad(id){
var file=document.getElementsByName("file");
var fileName=file[id-1].value;
xmlHttp=createXmlHttp();
xmlHttp.onreadystatechange=handlecallback;
var url="servlet/UpLoad?fileName="+fileName；
xmlHttp.open('post',url,true);
xmlHttp.send(null);
}
</script>

==================================================

servlet
============================================
    //  request.setCharacterEncoding("gb18030");
       
File file = new File(request.getParameter("fileName"));

这里的fileName就出现中文乱码了，请问高手有什么办法解决，我的tomcat，eclipse编码已经全部是utf-8的了。

---

String