⏰ 🐟 ☺️ Односторонние и двусторонние отношения в Hibernate 🔃 💬 ✊

, Hibernate JPA. :

OneToOne -
OneToMany -
ManyToOne -
ManyToMany -

, , , . , - Hibernate ;) (unidirectional) (bidirectional), , .

: . , , .

, . . , . Hibernate , .

. .

@Entity
@Table(name = "contacts")
public class Contact {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;

    @Column
    private String type;

    @Column
    private String data;

    @ManyToOne
    private User user;
    
    //   , ,   ..
}

@Entity
@Table(name = "users")
public class User {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;

    @Column
    private String username;

    //   , ,   ..
}

, Hibernate , . user_id contacts.

create table contacts (
    id bigint not null auto_increment,
    data varchar(255),
    type varchar(255),
    user_id bigint,
    primary key (id)
) engine=InnoDB;
    
create table users (
    id bigint not null auto_increment,
    username varchar(128) not null,
    primary key (id)
) engine=InnoDB

Contact . , , . . user Contact User. .

@Entity
@Table(name = "contacts")
public class Contact {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;

    @Column
    private String type;

    @Column
    private String data;
    
    //   , ,   ..
}

@Entity
@Table(name = "users")
public class User {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;

    @Column
    private String username;

    @OneToMany
    private List<Contact> contacts;

    //   , ,   ..
}

, , Hibernate , .

create table contacts (
    id bigint not null auto_increment,
    data varchar(255),
    type varchar(255),
    primary key (id)
) engine=InnoDB;

create table users (
    id bigint not null auto_increment,
    username varchar(128) not null,
    primary key (id)
) engine=InnoDB;

create table users_contacts (
    User_id bigint not null,
    contacts_id bigint not null
) engine=InnoDB;

Hibernate (join table) users_contacts, contacts, . , , Hibernate . , - .

JoinColumn contacts.

    @OneToMany
    @JoinColumn(name = "user_id")
    private List<Contact> contacts;

user_id contacts, .

- (owning side) (inverse side). .. . , , . . .

@Entity
@Table(name = "users")
public class User {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;

    @Column
    private String username;

    @ManyToMany
    private List<Role> roles;

    //   , ,   ..
}

@Entity
@Table(name = "roles")
public class Role {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;

    @Column
    private String name;

    @ManyToMany
    private List<User> users;

    //   , ,   ..
}

. Hibernate , .

create table roles_users (
    Role_id bigint not null,
    users_id bigint not null
) engine=InnoDB;

create table users_roles (
    User_id bigint not null,
    roles_id bigint not null
) engine=InnoDB;

, . . Hibernate , , , . mappedBy. , , .

. . users Role .

    //   mappedBy -      - 
    @ManyToMany(mappedBy = "roles")
    private List<User> users;

Hibernate users_roles.

. , - (many), mappedBy @OneToMany

. ( Contact).

@Entity
@Table(name = "contacts")
public class Contact {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;

    @Column
    private String type;

    @Column
    private String data;

    @ManyToOne
    private User user;
    
    //   , ,   ..
}

@Entity
@Table(name = "users")
public class User {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;

    @Column
    private String username;

    @OneToMany(mappedBy = "user")
    private List<Contact> contacts;

    //   , ,   ..
}

Hibernate .

! , , ! , !

, !

Односторонние и двусторонние отношения в Hibernate

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