如何根据Jquery实现两级联动

<script language="javascript" type="text/javascript" >

$(function (){

      $.ajax({

            url:<select:link page="/tobaccoinfo.do?method=getBrandList" />,

            type: "get" ,

            dataType: "json" ,

            success: function (result){

                   var str="<option value=''>全部</option>" ;

                   for (var i=0;i<result.length;i++){

                        str+= "<option value="+result[i].id+">"+result[i].name+ "</option>" ;

                  }

                  $( "#brandid" ).html(str);

            }

      });

      $( "#brandid" ).change( function(){

             var brandid=$("#brandid" ).val();

            $.ajax({

                  url:<select:link page="/tobaccoinfo.do?method=getTobaccoName" />,

                  type: 'get' ,

                  data:{

                         'brandid' :brandid

                  },

                  dataType: 'json' ,

                  success: function (result){

                         var str="<option value=''>全部</option>" ;

                         for (var i=0;i<result.length;i++){

                              str+= "<option value="+result[i].id_+ ">"+result[i].name_+ "</option>" ;

                        }

                        $( "#tobaccoId" ).empty().html(str);

                  }

            });

      });

});

</script>

<body>卷烟品牌:<select:select property="brandid" addspacerow="false" style="width:100px" ></select:select>
卷烟名称:<select:select property="tobaccoId" addspacerow="false" style="width:120px" ></select:select></body>