在另一个实体中多次使用同一个实体

Question

我正在使用 JPA 和 Hibernate 实现一个 Spring Boot 服务器，其中有 2 个实体：Channel 和 Translation。

Channel 实体有两个字段（nameTranslations 和 descriptionTranslations 应包含法语和英语两种语言的频道名称和描述），其类型为 Translation，如下所述：

班级Channel

@Entity
@Table(name = "CHANNEL")
public class Channel {
  
    @Id
    @Column(name = "ID")
    private String id;

    @OneToOne(mappedBy = "channel", cascade = CascadeType.ALL)
    private Translation nameTranslations;

    @OneToOne(mappedBy = "channel", cascade = CascadeType.ALL)
    private Translation descriptionTranslations;

}

和

班级Translation

@Entity()
@Table(name = "TRANSLATION")
public class Translation {

    @Id
    @Column(name = "ID")
    private String id;
    
    @Column(length = 1024)
    private String en;
    
    @Column(length = 1024)
    private String fr;

}

我的问题是：如何实现前面描述的逻辑，以便 Channel 类中有 2 个 Translation 字段？到目前为止，我已经使用@OneToOne 注释进行了尝试，但它不起作用。

Answer 1

我不确定您要实现哪种映射，但这会起作用：

@Entity
@Table(name = "CHANNEL")
public class Channel {
  
    @Id
    @Column(name = "ID")
    private String id;

    @OneToOne(cascade = CascadeType.ALL)
    private Translation nameTranslations;

    @OneToOne(cascade = CascadeType.ALL)
    private Translation descriptionTranslations;
}

或者，如果您想要其他实体表上的列：

@Entity
@Table(name = "CHANNEL")
public class Channel {
  
    @Id
    @Column(name = "ID")
    private String id;

    @OneToOne(mapped="name", cascade = CascadeType.ALL)
    private Translation nameTranslations;

    @OneToOne(mapped="description", cascade = CascadeType.ALL)
    private Translation descriptionTranslations;
}

@Entity
@Table(name = "TRANSLATION")
public class Translation {

    @Id
    @Column(name = "ID")
    private String id;
    
    @Column(length = 1024)
    private String en;
    
    @Column(length = 1024)
    private String fr;

    @OneToOne
    private Channel name;

    @OneToOne
    private Channel description;
}

请参阅Hibernate ORM documentation for one-to-one associations。