java EJB3，带有多个结果的 JPA 错误是从 Query.getSingleResult() 返回的
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EJB3, JPA error with More than one result was returned from Query.getSingleResult()
提问by MYE
i have new problem with JPA in EJB3 my stacktrace are:
我在 EJB3 中遇到了 JPA 的新问题，我的堆栈跟踪是：
Caused by: javax.persistence.NonUniqueResultException: More than one result was returned from Query.getSingleResult()
at org.eclipse.persistence.internal.jpa.EJBQueryImpl.throwNonUniqueResultException(EJBQueryImpl.java:1207)
at org.eclipse.persistence.internal.jpa.EJBQueryImpl.getSingleResult(EJBQueryImpl.java:722)
at com.DAO.CartDAO.checkUserID(CartDAO.java:47)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
at org.glassfish.ejb.security.application.EJBSecurityManager.runMethod(EJBSecurityManager.java:1056)
at org.glassfish.ejb.security.application.EJBSecurityManager.invoke(EJBSecurityManager.java:1128)
at com.sun.ejb.containers.BaseContainer.invokeBeanMethod(BaseContainer.java:5292)
at com.sun.ejb.EjbInvocation.invokeBeanMethod(EjbInvocation.java:615)
at com.sun.ejb.containers.interceptors.AroundInvokeChainImpl.invokeNext(InterceptorManager.java:797)
at com.sun.ejb.EjbInvocation.proceed(EjbInvocation.java:567)
at com.sun.ejb.containers.interceptors.SystemInterceptorProxy.doAround(SystemInterceptorProxy.java:157)
at com.sun.ejb.containers.interceptors.SystemInterceptorProxy.aroundInvoke(SystemInterceptorProxy.java:139)
at sun.reflect.GeneratedMethodAccessor206.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
at com.sun.ejb.containers.interceptors.AroundInvokeInterceptor.intercept(InterceptorManager.java:858)
at com.sun.ejb.containers.interceptors.AroundInvokeChainImpl.invokeNext(InterceptorManager.java:797)
at com.sun.ejb.co
i create one commandbutton to use for add item to cart, and i write one method to add item to cart in DB, i was check if userid and itemid != null, item quantity will add to 1, it mean when i have userid 1 add itemid 1 into cart, my method will check if it existed, item quantity will add 1 to item quantity in cart table, i can do it with one item, but if i add more item two into cart, it mean i add itemid is 2 into cart table, next i add more quantity of itemid 1 into db it throw exception More than one result. . . i know it can't have two instance at the same time, but i don't know how to solve it? Please help me
我创建了一个用于将商品添加到购物车的命令按钮，并且我编写了一种将商品添加到数据库中的购物车的方法，我正在检查用户 ID 和商品 ID 是否为空，商品数量将添加为 1，这意味着当我有用户 ID 1 时将 itemid 1 添加到购物车中，我的方法将检查它是否存在，商品数量会将购物车表中的商品数量加 1，我可以用一件商品来完成，但是如果我将更多商品 2 添加到购物车中，则意味着我添加的商品是2 到购物车表中，接下来我将更多数量的 itemid 1 添加到 db 中，它会抛出异常多个结果。. . 我知道它不能同时有两个实例，但我不知道如何解决？请帮我
my addTocart method
我的 addTocart 方法
public void addtoCart(Items item){
this.items = item;
if(cartDAO.checkUserID(getMemberLoginController().getUser().getUserid()) != null &&
cartDAO.checkItemid(items.getItemid()) != null){
cart = cartDAO.checkUserID(getMemberLoginController().getUser().getUserid());
int updateQuantity = cart.getCartQuantity() + 1;
cart.setCartQuantity(updateQuantity);
// chuyen so luong sang kieu du lieu big decimal
java.math.BigDecimal bigQuantity = new java.math.BigDecimal(String.valueOf(updateQuantity));
// so tien cua san pham = so luong x don gia
BigDecimal updatePrice = items.getPrice().multiply(bigQuantity);
cart.setPrice(updatePrice);
cart = cartDAO.updateCart(cart);
}else if(cartDAO.checkUserID(getMemberLoginController().getUser().getUserid()) != null &&
cartDAO.checkItemid(items.getItemid()) == null){
cart = cartDAO.checkUserID(getMemberLoginController().getUser().getUserid());
cartPk.setUserid(getMemberLoginController().getUser().getUserid());
cartPk.setItemid(item.getItemid());
cart.setCartPK(cartPk);
cart.setCartQuantity(1);
cart.setPrice(item.getPrice());
cart = cartDAO.addCart(cart);
}else {
cartPk.setItemid(item.getItemid());
cartPk.setUserid(getMemberLoginController().getUser().getUserid());
cart.setCartPK(cartPk);
cart.setCartQuantity(1);
cart.setPrice(item.getPrice());
cart = cartDAO.addCart(cart);
}
}
my select statement
我的选择语句
@NamedQuery(name = "Cart.findByUserid", query = "SELECT c FROM Cart c WHERE c.cartPK.userid = :userid")
my checkuseridMethod
我的 checkuserid 方法
public Cart checkUserID(int id){
Cart cart = null;
try {
Query query = em.createNamedQuery("Cart.findByUserid");
query.setParameter("userid", id);
return (Cart) query.getSingleResult();
} catch (NoResultException e) {
return null;
}
}
回答by Bozho
Well, it seems like your database has more carts for this user (which is a plausible scenario if you store user history)
好吧，您的数据库似乎为该用户提供了更多购物车（如果您存储用户历史记录，这是一个合理的场景）
You can either make sure that there is no more than one record in the database (by deleting older carts when a new one is created, for example), or use Query.setMaxResults(1)and something like ORDER BY dateCreatedin your query.
您可以确保数据库中的记录不超过一条（例如，通过在创建新购物车时删除旧购物车），或者在查询中使用Query.setMaxResults(1)类似ORDER BY dateCreated的内容。
