利用jsp购物车计算总价

怎么计算小计总价，

 /*购物车类*/
public class MyCart extends HashMap{
    private String myCartName;

    public MyCart(){
        this("myCart");
    }

    public MyCart(String name){
        this.myCartName = name;
    }

    public String getName(){
        return this.myCartName;
    }
}

对购物车的操作：

 //这是购物车的操作类,为了保证一个客户端只能new一个购物车,MyCartBO只能new一次
public class MyCartBO {
    private MyCart myCart = new MyCart("我的购物车");
    private Connection ct;
    private Statement sm;
    private ResultSet rs;

    //根据商品id号删除记录
    public void delGoodsById(int goodsId){
        this.myCart.remove(goodsId);
    }

    //跟据商品id返回数量
    public int getGoodsNumById(int goodsId){
        int numbers = (int)this.myCart.get(goodsId);

        return numbers;
    }

    //添加商品
    public void addGoods(int goodsId){
        if(this.myCart.get(goodsId) == null){
            myCart.put(goodsId, 1); 
        }else{
            this.upGoodsNum(goodsId, (int)myCart.get(goodsId) + 1);
        }

    }

    //修改商品数量
    public void upGoodsNum(int goodsId, int newNum){
        myCart.put(goodsId, newNum);
    }

    //删除所有的商品
    public void delAllGoods(){
        myCart.clear();
    }

    //返回购物车的商品信息
    public ArrayList getGoodsOrder(){
        ArrayList al = new ArrayList();

        try{
            if(this.myCart.size() == 0){
                return al;
            }

            String sql = "select * from goods where goodsId in(";

            //从购物车中获得所有的GoodsId号
            Iterator it = myCart.keySet().iterator();

            while(it.hasNext()){
                int key = (int)it.next();
                if(it.hasNext()){
                    sql += key;
                    sql += ",";
                }else{
                    sql += key;
                    sql += ")";
                }
            }

            ct = new ConnDB().getConn();
            sm = ct.createStatement();
            rs = sm.executeQuery(sql);

            while(rs.next()){
                GoodsBean gb = new GoodsBean();
                gb.setGoodsId(rs.getInt(1));
                gb.setGoodsName(rs.getString(2));
                gb.setGoodsIntro(rs.getString(3));
                gb.setGoodsPrice(rs.getFloat(4));
                gb.setGoodsNum(rs.getInt(5));
                gb.setPublicsher(rs.getString(6));
                gb.setPhoto(rs.getString(7));
                gb.setType(rs.getString(8));

                al.add(gb);
            }

        }catch(Exception ex){
            ex.printStackTrace();
        }finally{
            this.close();
        }

        return al;
    }

    /*
    //返回购物车的商品信息,这个算法废弃,原因是查询数据库次数太多,需要优化
    //缺点之处在于:每得到个goodsId就取数据库查询一次，然后封装到GoodsBean
    public ArrayList getGoodsOrder(){
        ArrayList al = new ArrayList();

        try{
            //遍历HashMap中的所有key,获取购物车中的所有key
            Iterator it = this.myCart.keySet().iterator();
            while(it.hasNext()){
                int key = (int)it.next();
                //获得一个key查询一次
                String sql = "select * from goods where goodsId=" + key + "";

                ct = new ConnDB().getConn();
                sm = ct.createStatement();
                rs = sm.executeQuery(sql);
                if(rs.next()){
                    GoodsBean gb = new GoodsBean();
                    gb.setGoodsId(rs.getInt(1));
                    gb.setGoodsName(rs.getString(2));
                    gb.setGoodsIntro(rs.getString(3));
                    gb.setGoodsPrice(rs.getFloat(4));
                    gb.setGoodsNum(rs.getInt(5));
                    gb.setPublicsher(rs.getString(6));
                    gb.setPhoto(rs.getString(7));
                    gb.setType(rs.getString(8));

                    al.add(gb);
                }
            }

        }catch(Exception ex){
            ex.printStackTrace();
        }finally{
            this.close();
        }

        return al;
    }
    */

    //关闭数据库资源
    private void close(){
        try{
            if(rs != null){
                rs.close();
            }
            if(sm != null){
                sm.close();
                sm = null;
            }
            if(ct != null){
                ct.close();
                ct = null;
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }

    public float getTotalPrice(){
        float totalPrice = 0.0f;

        //从购物车中获取所有的GoodsBean
        ArrayList al = this.getGoodsOrder();
        for(int i = 0; i < al.size(); i++){
            GoodsBean gb = (GoodsBean)al.get(i);
            int goodsId = gb.getGoodsId();

            //totalPrice = 商品个数 x 商品价格
            int num =(int)this.myCart.get(goodsId);
            float goodsPrice = gb.getGoodsPrice();

            totalPrice += num*goodsPrice;
        }

        //对总价四舍五入,留小数点两位
        totalPrice = ((int)(totalPrice*100)) / 100.0f;

        return totalPrice;
    }
}

计算购物车总价格是在前台，可以通过js进行计算的。

参考

 http://www.cnblogs.com/come-on/archive/2016/02/04/5182409.html