modify getCartItems
modify addToCart
modify cart.html
modify getTotalMoney method
remove useless code
modify changeCount method
modify changeCount
modify getTotalCount method
modify order.html
modify toUpdate product
modify doUpdate product
modify add category method
modify getCategoryById method
format code
modify add to cart
modify productInfo
add deleteCart interface
modify changeCount method
add deleteCartItem method
add test should_delete_all_cartitems