spring mvc 2个select框取值

function test(){
var pro=$("#activity_project").val();
$.ajax({
type: "POST",
url: "${pageContext.request.contextPath}/video/selectchild",
data: { //发送给数据库的数据
idKey:pro
},
dataType: 'json',
success: function(data) {
$("#activity_taskid").empty();
$.each(data.tasks, function(index,item){
//alert(item.specification);
//$("#activity_taskid").empty();
$("#activity_taskid").append("<option>"+item.specification+"</option>");
});
}

});

}

<tr><td>频道:</td><td><sf:select id="activity_project" path="category" onchange="test()" style="width:150px">

<sf:option value="0">--请选择--</sf:option>
<sf:options items="${categoryList}"/>
</sf:select></td></tr>
<tr><td>栏目:</td>
<td>
<sf:select id="activity_taskid" path="colunm" style="width:150px">
<sf:option value="0" id="selectchild">--请选择--</sf:option>
</sf:select></td></tr>

List<Category> categoryListchild=null;
categoryListchild=videoService.getlist(hql);
Map josnMap = new HashMap();
List list=new ArrayList();
if(categoryListchild.size()>0){
for(int i=0;i<categoryListchild.size();i++){
String name=categoryListchild.get(i).getName();
Map taskMap=new HashMap();
taskMap.put("specification",name);
list.add(taskMap);
}
}
josnMap.put("tasks",list);
return JSONObject.fromObject(josnMap);