/*
     * 添加到购物车
     * */
    public String addToCart(){
        
        //-------------------------------------
        Map session = ActionContext.getContext().getSession();  
        if(session.get("cart")==null){
            List<Book> cart = new ArrayList<Book>();
            session.put("cart",cart);
        }
        
        Book b = bookService.queryById(bookId, false);
            b.setBookId(bookId);
        // 标记添加的商品是否是同一件商品
        boolean same = false;
        List<Book> cart = (List<Book>) session.get("cart");
        if(cart.size()==0){
            b.setCount(b.getCount() + 1);
            cart.add(b);
        }else{
            for (Book bo : cart) {
                if(bo.getBookId() == this.getBookId()){
                    // 购买相同的商品，更新数量
                    bo.setCount(bo.getCount() + 1);
                    same = true;
                }
            }
            if(!same){
                Book b2 = bookService.queryById(bookId, false);
                b2.setCount(b2.getCount() + 1);
                cart.add(b2);
            }
            session.put("cart", cart);
        }
        return "addToCart_success";
    }