springMvc Jsp下拉框(select)级联

jsp页面信息:

<form action="corp_cost/save.do" name="Form" id="Form" method="post">

<tr>
<td style="width:70px;text-align: right;padding-top: 13px;">资费类型:</td>

                <td>
<label style="float:left;padding-left: 10px;"><input name="form-field-radio" id="form-field-radio1" type="radio" value="1" checked="checked"><span class="lbl">包时长</span></label>
<label style="float:left;padding-left: 10px;"><input name="form-field-radio" id="form-field-radio2" type="radio" value="2"><span class="lbl">套餐</span></label>
<label style="float:left;padding-left: 10px;"><input name="form-field-radio" id="form-field-radio3" type="radio" value="3"><span class="lbl">计时</span></label>
</td>
</tr>
<tr>
<td style="width:70px;text-align: right;padding-top: 13px;">资费名称:</td>

                <td>
<select class="costId_chzn_o_1"
name="costId" id="cost_all" data-placeholder="请选择资费"
style="vertical-align:top;width: 180px;"
>
<option value=""></option>
<option value="">全部</option>
</select>
</td>
</tr>
<tr>
<td style="text-align: center;" colspan="10">
<a class="btn btn-mini btn-primary" onclick="save();">保存</a>
<a class="btn btn-mini btn-danger" onclick="top.Dialog.close();">取消</a>
</td>
</tr>
</table>
</div>

</form>

<script type="text/javascript">

$(function() {
//页面初始化时级联默认信息
getCosts();

//单选按钮触发时级联信息
$('input:radio[name="form-field-radio"]').change(function(){
getCosts();
});

});

function getCosts(){
var costType = $('input:radio[name="form-field-radio"]:checked').val();
$.ajax({
type: "POST",
url: '<%=basePath%>corp_cost/getCosts.do',
data: {cost_type: costType},
dataType:'json',
beforeSend: function(){
   //级联信息时首先清空下拉框信息
$(".costId_chzn_o_1").html('请选择');
},
success: function(data){
var str = '<option value="">请选择</option>';
for(var o in data){
str += "<option>"+data[o].name+ "</option>";
}
$(".costId_chzn_o_1").append(str);
}
});
}

</script>

controller类代码

@ResponseBody
@RequestMapping(value="/getCosts" , produces = {"application/json;charset=UTF-8"})
public String getCosts() throws Exception{
List<Map> costs = costService.listAll(pd);  //这里返回list对象,map中包含key=name
return JSONObject.toJSONString(costs);

}