使用servlet填充另一个更改的下拉列表

我是java struts的新手，我正在struts 1.3中开发Web应用程序，我有两个下拉菜单，一个是用于位置，另一个是用于Floor，我要求更改数据库中其他下拉菜单填充的一个下拉菜单值谷歌搜索了很多代码，但是当我在第一个下拉菜单中进行更改时，第二个下拉菜单并未填充，尽管我在Netbeans的调试模式下看到该值从数据库返回.我在servlet doGet方法中执行数据库活动

i am new in java struts i am developing web application in struts 1.3 i have two dropdowns one is for location and another is for Floor,i have a requirement that on change on one dropdown values of other dropdown fills from database for i googled a lot and i got code but when i change on my first dropdown second dropdown does not populate though i saw in debugging mode in Netbeans that that values return from database .i do my database activity in servlet doGet method

 <script>
 function createRequestObject()
 {

 var req;

 if(window.XMLHttpRequest)
 {
 //For Firefox, Safari, Opera
 req = new XMLHttpRequest();
 }
 else if(window.ActiveXObject)
 {
 //For IE 5+
 req = new ActiveXObject("Microsoft.XMLHTTP");
 }
 else
 {
 //Error for an old browser
 alert('Your browser is not IE 5 or higher, or Firefox or Safari or Opera');
 }

 return req;
 }

 //Make the XMLHttpRequest Object
 var http = createRequestObject();

 function sendRequest(method, url)
 {

 if(method == 'get' || method == 'GET')
 {

 http.open(method,url);
 http.onreadystatechange = handleResponse;
 http.send(null);
 }
 }

 function handleResponse()
 {

 if(http.readyState == 4 && http.status == 200)
 {

 var response = http.responseText;
 if(response)
 {

 document.getElementById("dwnfloor").innerHTML = response;
 }
 }
 }

 function getFloorDropdown(SelectedValue)
 {
 alert(SelectedValue);
 sendRequest('GET','http://localhost:8084/AssetManagement/DropDown?locid='  +SelectedValue );
 }

 </script>

 <tr>
 <td >
 <span style="color:#FF0000">*</span>Location</td>
 <td> <html:select name="RoomForm" property="name"
 onchange="getFloorDropdown(this.value)">
 <htmlption value="0">Select Location</htmlption>
 <htmlptionsCollection name="RoomForm"
 property="list" value="id" label="name" />
 </html:select>
 <td>
 </tr>
 <tr>
 <td >
  <span style="color:#FF0000">*</span>Floor
 </td>
<td id="dwnfloor">

<select name="dwnfloor">
<option value="0">Select Floor</option>
</select>
</td>
</tr>

Servlet代码

protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

    processRequest(request, response);
    String country=request.getParameter("locid");
    String buffer="<select name=\"dwnfloor\"><option value=\"0\">Select</option>";
    Connection connection = null;
    PreparedStatement p_statement = null;
    Statement statement = null;
    ResultSet result = null;

    try {
        DAOOperation dao= new DAOOperation();
        String sqlst = "select id,name from floor_mst where id=?";
        try {
            connection = DBConnection.getConnection();
            p_statement = connection.prepareStatement(sqlst);
            p_statement.setString(1, country);
            result = p_statement.executeQuery();

            while(result.next()) {
                buffer=buffer+"<option value=\""+result.getString("ID")+"     \">"+result.getString("name")+"</option>";
            }

            buffer=buffer+"</select>";
            response.getWriter().println(buffer);
            System.out.println(buffer);
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            try {
                connection.close();
            } catch (Exception e) {
            }
        }// end finally
    } catch(Exception e) {
        System.out.println(e);
    }
}

和web.xml中的servlet映射

web.xml

<servlet-mapping>
<servlet-name>DropDown</servlet-name>
<url-pattern>/DropDown</url-pattern>
</servlet-mapping>