对象名称“ACCOUNT_orders”无效？带有注释问题的 Spring-MVC Hibernate

Question

我是 Hibernate 的新手。我在 DB 中有 Order 和 Account 表，

CREATE TABLE [dbo].[ORDERS](
    [PRICE] [decimal](12, 2) NULL,
    [ORDERID] [int] IDENTITY(0,1) NOT NULL,
    [ACCOUNT_ACCOUNTID] [int] NULL,
 CONSTRAINT [PK_ORDER] PRIMARY KEY CLUSTERED 
(
    [ORDERID] ASC
)WITH (  STATISTICS_NORECOMPUTE  = OFF, IGNORE_DUP_KEY = OFF )  
)  

账户表：

CREATE TABLE [dbo].[ACCOUNT](
    [BALANCE] [decimal](12, 2) NULL,
    [ACCOUNTID] [int] IDENTITY(0,1) NOT NULL,
    [PROFILE_USERID] [varchar](250) NULL,
 CONSTRAINT [PK_ACCOUNT] PRIMARY KEY CLUSTERED 
(
    [ACCOUNTID] ASC
)WITH (  STATISTICS_NORECOMPUTE  = OFF, IGNORE_DUP_KEY = OFF )  
)

我正在尝试进行一对多映射，一个帐户有很多订单。我有以下课程：

@Table(name="ACCOUNT")
public class Account implements Serializable, IEntity{

    private static final long serialVersionUID = 1L;
    private int accountID;
    private double balance;
    private List<Order> orders; 

    @Id
    @GeneratedValue
    public int getAccountID() {
        return accountID;
    }
public void setAccountID(int accountID) {
    this.accountID = accountID;
}

public double getBalance() {
    return balance;
}
public void setBalance(double balance) {
    this.balance = balance;
}

@OneToMany(cascade = CascadeType.ALL,fetch = FetchType.EAGER)
@JoinColumn(name = "ACCOUNT_ACCOUNTID",nullable=false,insertable=true,updatable=true)
public List<Order> getOrders()
{
    return orders;
}  
public void setOrders(List<Order> orders)
    {
        this.orders = orders;
    }       
}

订单类别：

@Table(name="ORDERS")
public class Order implements Serializable, IEntity
{
    private int orderID;
    private double price;
    @Column(name="ACCOUNT_ACCOUNTID")
    private Account account; 

    @Id
    @GeneratedValue
    public int getOrderID() {
    return orderID;
}
public void setOrderID(int orderID) {
    this.orderID = orderID;
}
public double getPrice() {
    return price;
}
public void setPrice(double price) {
    this.price = price;
}

@ManyToOne(cascade = CascadeType.ALL ,fetch = FetchType.EAGER)
public Account getAccount() {
        return account;
    }
    public void setAccount(Account account) {
        this.account = account;
    }  
}

但是当我尝试使用以下 HQL 访问 HibernateTemplate 的 List 方法时：

SQL_QUERY =" from Account as a where a.balance='"+bal+"'";

它给了我以下异常：

(JDBCExceptionReporter.java:72) - Invalid object name 'ACCOUNT_orders'.

java.lang.NullPointerException
    at com.microsoft.trade.service.TradeServiceImplementor.loginVerify(TradeServiceImplementor.java:59)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)

请帮帮我。提前致谢。

Answer 1

这里有一个双向的 OneToMany 关联：一个账户有很多订单，一个订单有一个账户。其中一个关联与另一个相反。因此，您必须在一侧（通常是多侧：这是 JPA 规定的）定义此关联的映射，并声明该关联与另一侧（一侧）的另一个相反：

@Entity
public class Account implements Serializable, IEntity{
    // ...
    private List<Order> orders; 

    // mappedBy is used to indicate that this association is the inverse of the association
    // mapped by the account property of the Order entity
    @OneToMany(cascade = CascadeType.ALL, fetch = FetchType.EAGER, mappedBy="account")
    public List<Order> getOrders() {
        return orders;
    }       
}

@Entity
public class Order implements Serializable, IEntity {
    // ...
    // a relationship to another entity is never mapped by @Column. You can't have annotations 
    // on the field and the getter. Choose one or the other, and be consistent for all 
    // the properties of the entity
    private Account account; 

    @ManyToOne(fetch = FetchType.EAGER)
    @JoinColumn(name = "ACCOUNT_ACCOUNTID")
    public Account getAccount() {
        return account;
    }  
}

请注意，大多数情况下，在关系的多方面都存在级联是错误的。您不希望在下订单时删除帐户，对吗？账户持有订单，而不是相反。

最后，关于您的查询：这不是 SQL 查询，而是 HQL 查询。而且你不应该使用连接，而是绑定参数：这样更安全（没有注入攻击）、更清晰（不需要引用、更易读）、更快：

String hql = "from Account a where a.balance = :theBalance";
Query query = session.createQuery();
query.setParameter("theBalance", new BigDecimal("12.5");