java购物车用servlet做，sql数据库，能实现基本增加、删除、修改商品，结账，然后下订单，求源代码

加入购物车的代码:
//把商品保存到session中
HttpSession session=request.getSession();

List list=(List) session.getAttribute("list");
int gid=Integer.parseInt(request.getParameter("gid"));
int num=Integer.parseInt(request.getParameter("num"));
Goods goods=null;

if(list==null || list.size()<0){
list=new ArrayList();
}else{
for (Goods g : list) {
if(g.getGid()==gid){
goods=g;
g.setSum(g.getSum()+num);
break;
}
}
}

if(goods==null){
goods=goodsDao.queryGoodsByG_id(gid);
goods.setSum(num);
list.add(goods);
}
session.setAttribute("list", list);
request.getRequestDispatcher("/index.jsp").forward(request, response);

增加、删除、修改商品差不多，只是sql语句不同