data:[{   userName:encodeURI(encodeURI('中文字段'))  }]

const jsonData = []
// room/cust_name 属性值有中文
for (var i = 0; i < selectedData.length; i++) {
  jsonData.push({
    room: selectedData[i].roomname,
    cust_name: selectedData[i].cust_name,
    attach_path: selectedData[i].attach_path
  })
}
const saveData = JSON.stringify(jsonData)
window.open('http://127.0.0.1:8080/BackGround/sub/BatchExport.do?json='+encodeURI(encodeURI(saveData)))

String chData= ParamUtil.getString(request, "chData"); 
chData= java.net.URLDecoder.decode(chData,"UTF-8"); 

String json=request.getParameter("json");   //json对象 
json=URLDecoder.decode(json,"UTF-8");