java - 如何对非 PK id 使用 @TableGenerator 注解

Question

这是 JPA 实体架构的摘录

    @Entity
    @Table(name="customer")
    public class Customer implements Serializable {

        @Id
        @GeneratedValue(strategy = GenerationType.AUTO)
        @Column(name="customer_id")
        private Long id;

        @ManyToOne
        @JoinColumn(name="company_id",nullable=false)
        private Company company;

    //...

    }

    @Entity
    @Table(name="company")
    public class Company implements Serializable {

        @Id
        @GeneratedValue(strategy = GenerationType.AUTO)
        @Column(name="company_id")
        private Long id;

    //...

    }

    @Entity
    @Table(name="order_header")
    public class OrderHeader implements Serializable {

        @Id
        @GeneratedValue(strategy = GenerationType.AUTO)
        @Column(name="order_id")
        private Long id;


        @ManyToOne
        @JoinColumn(name="customer_id",nullable=false)
        private Customer customer;

        private Long internalCompanyOrderId;

    //...

    }

我需要为每个 Company_id 检索唯一的内部CompanyOrderId 序列。这意味着尽管如此，订单 PK 仍将是“order_id”，我需要每个公司的“内部”order_id。

Answer 1

您的代码示例中没有出现 @TableGenerator。我假设您想使用 @GenerateValue 生成值。

对于 JPA 2.0，根据规范，您不能对不属于主键的字段使用 @GenerateValue:

The GeneratedValue annotation may be applied to a primary key property or field of an entity or mapped superclass in conjunction with the Id annotation. [97]
...
[97] Portable applications should not use the GeneratedValue annotation on other persistent fields or properties.