JPA：在一個表中的主鍵列和另一個表中的非主列之間創建約束？

Question

我使用JPA，並試圖找出如何在一個表中，而在另一個非主鍵列創建一個主鍵列之間的唯一約束。我有兩個表：

Customer (
    id character varying(32) NOT NULL, 
    customer_name character varying(50) 
) 

和

Account (
    id character varying(32) NOT NULL, 
    account_name character varying(50) 
) 

有一個單向的，一到許多與約束Account.account_name是每個客戶獨特的客戶和客戶之間的關係。代碼看起來像這樣：

@Entity 
public class Customer { 
    @Id 
    @Column(length=32) 
    private String id; 

    @Column(unique=true, length=50) 
    private String customer_name; 

    @OneToMany 
    private List<Account> accounts; 
    ... 
} 

和

@Entity 
public class Account { 
    @Id 
    @Column(length=32) 
    private String id; 

    @Column(length=50) 
    private String account_name; 
    ... 
} 

連接表默認創建：

CUSTOMER_ACCOUNTS (
    customer_id character varying(32), 
    accounts_id character varying(32) 
) 

如何創建唯一約束，以確保Account.account_name是每個客戶獨特？

Answer 1

添加JoinColumn註解Customer類::

@Entity 
public class Customer { 
    @Id 
    @Column(length=32) 
    private String id; 

    @Column(unique=true, length=50) 
    private String customer_name; 

    @OneToMany(mappedBy="customer") 
    @JoinColumn(name="CUSTOMER_ID", referencedColumnName="ID") 
    private List<Account> accounts; 
    ... 
} 

引用的列名指向Customer表的主鍵，而名稱指向Account表的外鍵字段。 此外，還應CUSTOMER_ID字段和複合唯一約束添加到該帳戶實體：

@Entity 
@Table(
    uniqueConstraints= 
     @UniqueConstraint(columnNames={"CUSTOMER_ID", "ACCOUNT_NAME"}) 
) 
public class Account { 
    @Id 
    @Column(length=32) 
    private String id; 

    @Column(length=50) 
    private String account_name; 

    @Column(name="CUSTOMER_ID") 
    private String customer_id; 
    ... 
}