java - 如何使用 Hibernate 连接两个表的字段？

Question

我有两个表和相关的 Java 映射。

CREATE TABLE country (
    code VARCHAR(3) PRIMARY KEY NOT NULL,
    name VARCHAR(100) NOT NULL
);


CREATE TABLE user (
    id INT PRIMARY KEY NOT NULL AUTO_INCREMENT,
    name VARCHAR(100) NOT NULL,
    country_code VARCHAR(3),
    FOREIGN KEY ( country_code ) REFERENCES country ( code )
);

这是我的 Java 实体。国家 POJO:

@Entity
@Table(name = "country")
public class Country {

    @Id
    @Column (name = "code")
    private String code;

    @Column (name = "name")
    private String name;

和用户 POJO:

@Entity
@Table(name = "user")
public class User implements Serializable {

    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    private Integer id;

    @Column(name = "name")
    private String name;

    @Column(name = "country_code")
    private String countryCode;

问题是如何在 Hibernate 中使用注解将 Contry.code 加入到 User.countryCode 中？当我使用 Hibernate 创建用户对象时，我需要自动绑定(bind)这两个字段(代码和国家/地区代码)。

Answer 1

您需要从 Country 到 User 实体的 @OneToMany 映射以及从 对应的 @ManyToOne 映射用户到国家:

@Entity
@Table(name = "country")
public class Country {

    @Id
    @Column (name = "code")
    private String code;

    @Column (name = "name")
    private String name;

    @OneToMany(mappedBy = "country")
    private Set<User> users;
}

@Entity
@Table(name = "user")
public class User implements Serializable {

    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    private Integer id;

    @Column(name = "name")
    private String name;

    @ManyToOne
    @JoinColumn(name = "country_code")
    private Country country;
}