easyui treegrid逐步加载

$("#bomStructureTable").treegrid({
url : "systemcontroller?id=10007",//首次查询路径
queryParams:{"bomid":"${bomid}"},//首次查询参数
columns : [ [{
field : "name",
title : "名称",
width : 300
} ] ],
onBeforeExpand:function(row){
//动态设置展开查询的url
var url = "systemcontroller?id=10007&treeid="+row.treeid;
$("#bomStructureTable").treegrid("options").url = url;
return true;
}
});