select菜单实现二级联动

<tr>                <th>执行人<b>*</b></th>                <td>                    <select name="jdcld.ZXDW" id="zxrDw" onchange="zxDwChange()" class="select" style="width:230px">                        <option value="">选择部门</option>                    <#if zxrBm??&&zxrBm?size!=0>                        <#list zxrBm as bm>                            <option value="${bm['id']}">${bm['mc']}</option>                        </#list>                    </#if>                    </select>                    <select name="jdcld.ZXRID" id="zxrId" class="select" style="width:230px">                        <option value="">选择民警</option>                    </select>                    <input type="hidden" name="jdcld.ZXRXM"/>                </td></tr>

function zxDwChange() {        var bmid = $("#zxrDw").val();        alert(bmid);        $("#zxrId").empty();        var text = "<option value=''>选择民警</option>";        $.post("${base}/zfjd/zxrList", {"bmid":bmid}, function(data) {            if (data != "") {                var dataArr = eval('(' + data + ')');                for (var i in dataArr) {                    text += "<option value='" + dataArr[i].value + "'>" + dataArr[i].title + "</option>";                }                if (text == "<option value=''>选择民警</option>") {                    $("#zxrId").append("<option value=''>选择民警</option>");                } else                    $("#zxrId").append(text);            } else {                $("#zxrId").append("<option value=''>选择民警</option>");            }        });    }

@Action("zxrList")    public void zxrList() {        try {            if (request.getParameter("bmid").equals("")) {            } else {                Integer bmid = Integer.parseInt(request.getParameter("bmid"));                zxr = policeMenService.getZxr(bmid);                String json = "[";                if (null != zxr && zxr.size() > 0) {                    for (Map map : zxr) {                        json += "{\"value\":\"" + map.get("id") + "\",\"title\":\"" + map.get("xm") + "\"},";                    }                    json = json.substring(0, json.length() - 1);                }                json += "]";                super.renderText(json);            }        } catch (Exception e) {            e.printStackTrace();        }    }