新手求教：ajax获得json数组，但取值显示undefined

Question

Javascript代码
function as(){
var xmlhttp;
    if (window.XMLHttpRequest)
  {// code for IE7+, Firefox, Chrome, Opera, Safari
  xmlhttp=new XMLHttpRequest();
  }
else
  {// code for IE6, IE5
  xmlhttp=new ActiveXObject("Microsoft.XMLHTTP");
  }
xmlhttp.open("post","NewFile.jsp",true);
xmlhttp.setRequestHeader("Content-Type","application/x-www-form-urlencoded");
xmlhttp.send("Parameters=8000482699");
xmlhttp.onreadystatechange=function()
  {
  if (xmlhttp.readyState==4 && xmlhttp.status==200)
    {
  var json= xmlhttp.responseText;
  document.getElementById("test_div").innerHTML=json;
  document.getElementById("test_div1").innerHTML=json.length;
  document.getElementById("test_div2").innerHTML=json[1].chargeItemName; 
    }
  }
}Jsp页面代码
List chargeJSONList=new ArrayList();
while(rs.next()){

String CItemName=rs.getString("ITEM_NAME");
String CSpecs=rs.getString("SPECS");
int CItemNum=rs.getInt("QTY");
String CItemUnit=rs.getString("PRICE_UNIT");
String CItemExec=rs.getString("EXEC_DPCD");
int CItemUnitprice=rs.getInt("UNIT_PRICE");
int CTotal=CItemNum*CItemUnitprice;
String CText=rs.getString("TEXT");

Charges charge=new Charges(); charge.setChargeItemName(CItemName);
charge.setChargeSpecs(CSpecs);
charge.setChargeItemNum(CItemNum);
charge.setChargeItemUnit(CItemUnit);
charge.setChargeItemExec(CItemExec);
charge.setChargeItemUnitprice(CItemUnitprice);
charge.setChargeTotal(CTotal);
charge.setChargeText(CText);

chargeJSONList.add(charge);

}
System.out.println(chargeJSONList);
JSONArray jsonarray = JSONArray.fromObject(chargeJSONList);
out.println(jsonarray);
System.out.println(jsonarray);

Answer 1

你这只是获取到json格式的字符串，并没有转换成js对象

Answer 2

var json= JSON.parse(xmlhttp.responseText);

Answer 3

 var dataJson = eval(data);

Answer 4

  var json=eval('('+ xmlhttp.responseText+')');
  document.getElementById("test_div").innerHTML=json;
  document.getElementById("test_div1").innerHTML=json.length;
  document.getElementById("test_div2").innerHTML=json[1].chargeItemName;