如何解决java中接收参数乱码的问题

<script>
function download(documentPath){
  var url = "<c:url value=&#39;/product/download.action?documentPath=&#39;/>"+documentPath;
  url = encodeURI(encodeURI(url));
  window.location.href=url;
}
</script>

String documentPath = (String) request.getParameter('documentPath');
documentPath = URLDecoder.decode(documentPath,"utf-8");

URLEncoder.encode(URLEncoder.encode("传递的中文","utf-8"));

URLDecoder.decode(request.getParameter('documentPath'),"utf-8");

String s = new String(filename.getBytes("ISO-8859-1"),"UTF-8");