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;

问题是我如何在Hibernate中使用注释加入Contry.code到User.countryCode ?当我用Hibernate创建User对象时，我需要自动绑定这两个字段(code和countryCode)。

Answer 1

需要从Country到User实体的@OneToMany映射和相应的从User到Country的@ManyToOne映射:

@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;
}