Hibernate JPA 雙向一對多/多對一設定 Bidirectional One To Many / Many To One

一個作者(Author)有多本書(Book)，JPA 雙向一對多/多對一實體關聯設定如下。

Author.java

@Entity
@Table(name="Author")
public class Author {
    
    @Id
    @Column(name="AuthorId")
    private Integer authorId;
    
    @Column(name="AuthorName")
    private String authorName;
    
    @OneToMany(mappedBy="author")
    private Set&t;Book> bookSet;

    // getter and setter ommitted...
}

Book.java

@Entity
@Table(name="Book")
public class Book {
    
    @Id
    @Column(name="BookId")
    private Integer bookId;
    
    @Column(name="BookName")
    private String bookName;
    
    @ManyToOne
    @JoinColumn(name="AuthorId") // 外鍵欄位名稱
    private Author author; // 外鍵屬性

    // getter and setter ommitted...
}

@JoinColumn要放在外鍵所在的實體(owning side)的外鍵屬性。Book持有Author的外鍵，所以@JoinColumn放在Book.author

@OneToMany放在non owning side的實體，並設定mappedBy，其值為關係實體外鍵屬性的名稱。

參考：

• Hibernate JPA 雙向關係 Bidirectional Relationships 的意思
• Spring Data JPA @OneToMany LazyInitializationException could not initialize proxy - no Session
• JPA JoinColumn vs mappedBy
• What is the difference between Unidirectional and Bidirectional JPA and Hibernate associations?
• Hibernate/JPA ManyToOne vs OneToMany
• JPA: Determining the Owning Side of a Relationship
• In a bidirectional JPA OneToMany/ManyToOne association, what is meant by “the inverse side of the association”?
• JPA - Bidirectional OneToMany/ManyToOne Example