如何使用Hibernate连接两个表的字段? [英] How to join fields of two tables using Hibernate?
问题描述
CREATE TABLE country(
code VARCHAR(3)PRIMARY KEY NOT NULL,
name VARCHAR(100)NOT NULL
);
CREATE TABLE用户(
id INT PRIMARY KEY NOT NULL AUTO_INCREMENT,
name VARCHAR(100)NOT NULL,
country_code VARCHAR(3),
FOREIGN KEY(country_code)参考国家(代码)
);
这是我的Java实体。国家POJO:
pre code $ @ $实际
@Table(name =country)
public class Country {
@Id
@Column(name =code)
private String code;
@Column(name =name)
私有字符串名称;
和用户POJO:
@Entity
@Table(name =user)
public class User实现Serializable {
@Id
@GeneratedValue = GenerationType.AUTO)
private Integer id;
@Column(name =name)
私有字符串名称;
@Column(name =country_code)
private String countryCode;
问题是如何加入 Contry.code
到 User.countryCode
在Hibernate中使用注释?当我使用Hibernate创建User对象时,我需要自动将这两个字段(code和countryCode)绑定在一起。
从国家
到用户
实体和相应的<$ c的映射c $ c> @OneToMany $ c> @ManyToOne 从用户
到国家
的映射:
@Entity
@Table(name =country)
public class Country {
@ Id
@Column(name =code)
private String code;
@Column(name =name)
私有字符串名称;
@OneToMany(mappedBy =country)
private Set< User>用户;
$ b $实体
@Table(name =user)
public class User实现Serializable {
@Id
@GeneratedValue(strategy = GenerationType.AUTO)
private Integer id;
@Column(name =name)
私有字符串名称;
@ManyToOne
@JoinColumn(name =country_code)
私人国家国家;
}
I have two tables and related Java mapping.
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 )
);
Here is my Java entities. Country POJO:
@Entity
@Table(name = "country")
public class Country {
@Id
@Column (name = "code")
private String code;
@Column (name = "name")
private String name;
And User 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;
Question is how can I join Contry.code
to User.countryCode
in Hibernate using annotation? When I create User object with Hibernate I need to bind these two fields (code and countryCode) automatically.
You need @OneToMany
mapping from Country
to User
entity and corresponding @ManyToOne
mapping from User
to Country
:
@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;
}
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