ajax查詢資料庫，伺服器傳回json字串，js解析json

ajax查詢資料庫，伺服器傳回json字串，js解析json

伺服器端獲得要查詢的東西，查詢資料庫，將查詢的資訊，以json字串的形式返回給瀏覽器

public void doGet(HttpServletRequest request, HttpServletResponse response)            throws ServletException, IOException {        String departmentID=request.getParameter(departmentID);        DataBaseHandle dataBaseHandle=new DataBaseHandle(commonUser, common, jdbc:mysql://127.0.0.1:3306/firstwebsite);        String SQL=select * from speciality where departmentID='+departmentID+';        String json={'specialities':[;        response.setContentType(text/html; charset=utf-8);        response.setCharacterEncoding(UTF-8);        try {            ResultSet rs=dataBaseHandle.exeuteSQL(SQL);            while(rs.next())            {                json=json+{'+specialityID':'+rs.getString(1)+',+'SPname':'+rs.getString(2)+'},;                System.out.println(rs.getString(1)+rs.getString(2));            }            json=json.substring(0,json.length()-1);            json=json+]};            PrintWriter pwriter=response.getWriter();            pwriter.print(json);            rs.close();            dataBaseHandle.closeResourse();        } catch (SQLException e) {            // TODO Auto-generated catch block            e.printStackTrace();        }    }

js解析json，獲得返回的內容

   function updateSpeciality(str)        {            var xmlhttp;            if (str==)            {                alert(請選擇非空的值!);                return;            }            if (window.XMLHttpRequest)            {// code for IE7+, Firefox, Chrome, Opera, Safari                xmlhttp=new XMLHttpRequest();            }            else            {// code for IE6, IE5                xmlhttp=new ActiveXObject(Microsoft.XMLHTTP);            }            xmlhttp.onreadystatechange=function()            {                if (xmlhttp.readyState==4 && xmlhttp.status==200)                {                    var dataObj=eval((+xmlhttp.responseText+));//轉換為json對象                    for(var o in dataObj.specialities)                    {                        alert(dataObj.specialities[o].specialityID);                        alert(dataObj.specialities[o].SPname);                    }                }            }            xmlhttp.open(GET,/First/servlet/GetMessage?departmentID=+str,true);            xmlhttp.send();        }