MyBatis的SUM映射问题及解决

// mapper层
<select id="selectinfobytest" resulttype="map">
    select sum(flag) as flags,taskid from qcdata group by taskid
</select>
// 接口
list<hashmap<string, object>> selectinfobytest();
 
// 调用代码
list<hashmap<string, object>> result = qcdao.selectinfobytest();
int flags=(integer)result.get(0).get("flags"); // 报错
return jsonresult.ok(flags);

    public jsonresult test() {
        list<hashmap<string, object>> result = qcdao.selectinfobytest();  
        // tostring
        int flags=integer.parseint(result.get(0).get("flags").tostring()); 
        // string.valueof
        int flags2=integer.parseint(string.valueof(result.get(0).get("flags")));
        // 空字符串
        int flags3=integer.parseint(result.get(0).get("flags")+"");
        return jsonresult.ok(flags+flags2+flags3);
    }

 <select id="piechart"    resulttype="map">
       select   sum(com.thinkmoney*ord.commnumber)  as totalprice , com.category as  category  from commodity com,orders ord
        where com.commid=ord.commid and ord.orderstatus=1
        group by com.category
 </select>

 private static final long serialversionuid = 1l;
    /**
     * 订单id
     */
	private string id;
    /**
     * 订单编号
     */
	private string ordernumber;
    /**
     * 下单时间
     */
	private date ordertime;
    /**
     * 商品名
     */
	private string commname;
    /**
     * 商品id
     */
    private string commid;
    /**
     * 商品描述
     */
    private string commdesc;
    /**
     * 购买数量
     */
	private integer commnumber;
    /**
     * 商品单价
     */
	private bigdecimal price;
    /**
     * 收货地址
     */
	private string useraddress;
    /**
     * 订单状态 0未支付 1正常 2删除
     */
	private integer orderstatus;
    /**
     * 收货人
     */
	private string username;
    /**
     * 收货人手机号
     */
	private string mobilephone;
    /**
     * 发货状态 0未发货 1已发货 2确认收货
     */
	private integer kdstatus;
    /**
     * 快递编号
     */
	private string kdnumber;
    /**
     * 买家id
     */
	private string buyuserid;
    /**
     * 卖家id
     */
	private string selluserid;
	private  commodity commodity;
	private  bigdecimal  totalprice;

 /**
     * 管理员首页 饼图
     * */
    @getmapping("/echars/piechart")
    public string piechart(httpsession  session,httpservletrequest request){
        list<hashmap<string,object>>  result =ordersservice.piechart();
        list<string>  totalpricelist= new arraylist<string>();
        list<string>  categorylist= new arraylist<string>();
        for( map<string, object> maplist : result ) {
            totalpricelist.add(maplist.get("totalprice").tostring());
            categorylist.add(maplist.get("category").tostring());
        }
        session = request.getsession();
        system.out.println("totalpricelist:"+totalpricelist+",categorylist:"+categorylist);
        session.setattribute("totalpricelist",totalpricelist);
        session.setattribute("categorylist",categorylist);
        return "/admin/echars/piechart";
    }