如果用户再次添加，如何检查购物车中的现有商品并将其更新为1？

i have trouble with JPQL statement, i created NameQuery followed:

我有JPQL语句的问题，我创建了NameQuery跟随：

 @NamedQuery(name = "Cart.findExistCart", query = "SELECT c FROM Cart c WHERE  c.cartPK.userid = :userid AND c.cartPK.itemid = :itemid "),

in stateless bean i create one method to active this query followed:

在无状态bean中，我创建了一个方法来激活此查询：

 public Cart getUserItemCart(int userid,int itemid){

         Query query = em.createNamedQuery("Cart.findExistCart");
        // query.setParameter("userid", userid);
         query.setParameter("itemid", itemid);
         query.setParameter("userid", userid);

         return (Cart) query.getSingleResult();

     }

after that in JSF Managed Bean i create one method test if user id and item id are exist in DB it will print user id and itemid to server:

之后在JSF Managed Bean中我创建了一个方法测试，如果用户ID和项目ID存在于DB中，它会将用户ID和itemid打印到服务器：

public void addtoCart(Items item){
        this.items = item;
        int userid = getMemberLoginController().getUser().getUserid().intValue();
        int itemid = getItems().getItemid().intValue();
        if (cartDAO.getUserItemCart(userid, itemid) != null ){


              // cart = cartDAO.getUserItemCart(userid, itemid);
               cartPk.setUserid(userid);
               cartPk.setItemid(itemid);
               cart.setCartPK(cartPk);
               cart = cartDAO.getUserItemCart(userid, itemid);

               System.out.println(cart.getCartQuantity());


    }

but when client add item A into db and then add item B into db, and once again add item A into DB , it don't print item id of item id, it print item id of item B. Why? if i create select statement findByItemid, it work well if i do upon requirement it mean when click add A then click add B , and add A again it print id 1-2-1, but if i use select statement find Cart by ItemId and UserId it not work, it will print itemid is 1-2-2 What's happen with it?

但是当客户端将项目A添加到数据库中然后将项目B添加到数据库中，并再次将项目A添加到数据库中时，它不会打印项目ID的项目ID，它会打印项目B的项目ID。为什么？如果我创建select语句findByItemid，它可以很好地工作，如果我按照要求它的意思是当点击添加A然后单击添加B，并再次添加A它打印ID 1-2-1，但如果我使用选择语句查找按ItemId和UserId它不起作用，它会打印itemid是1-2-2它发生了什么？

1 个解决方案

#1

you can delete 2 line

你可以删除2行

       cartPk.setUserid(userid);
       cartPk.setItemid(itemid);

i think when you assign cart = cartDAO.getUserItemCart(userid, itemid);

我想当你分配cart = cartDAO.getUserItemCart（userid，itemid）;

the userid and itemid are have value.

userid和itemid有值。

#1