Question

我是Hibernate的新手。我在DB中有订单和帐户表，

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 )  
)

帐户表：

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 )  
)

我正在尝试做一对多的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：

@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+"'";

它给了我以下的ecxeption：

(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。在此先感谢。

Answer 1

您在这里有一个双向OneToMany关联：一个帐户有很多订单，一个订单有一个帐户。其中一个关联是另一个关联。因此，您必须在一侧定义此关联的映射（通常是多方：这是JPA规定的），并声明该关联是另一方（另一方）的另一方的反转：

@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，在关系的多方面都有级联是错误的。您不希望在订单时删除帐户，是吗？该帐户持有订单，而不是相反。

最后，关于你的查询：它不是SQL查询，它是一个HQL查询。并且你不应该使用连接，但是绑定参数：这更安全（没有注入攻击），更清晰（没有引用，更可读），并且更快：

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

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

1 个答案: