JS传值出现中文参数乱码的解决方法

function PopupFK(cNum,type){
  var url = "contract!Paying.action";
  url = url + "?contract.contractNum="+cNum+"&payingType="+type;
// if(isEmpty($(_this).attr("payId"))){
// url = url + "&s_paymentId="+paymentId;
// url = url + "&s_paymentDtlId="+paymentDtlId;
// }else{
// url = url + "&s_payId="+$(_this).attr("payId");
// }
  url = url+"&random="+Math.random();
  //在这里。用encodeURI进行两次转码。后台Action接收的时候。在进行一次。就不会出现乱码问题
  url = encodeURI(url);
  url = encodeURI(url);
　　var ret = window.showModalDialog(
  url,
  "",
  "dialogWidth=950px;dialogHeight=600px;center=yes;border=thick;status=no;help=no;scrollbars=no"
  );
}

String cNum = contract.getContractNum();
String Num;
try {
  Num = URLDecoder.decode(cNum,"utf8");
  System.out.println(Num);
  c = csl.queryOneByNum(Num);
} catch (UnsupportedEncodingException e) {
  throw new RuntimeException("合同数据错误，请联系管理员");
}