@Entity
@Table(name="authors")
public class Author {
    private Integer id;
    private String name;
    private Set<Book> books;

    public Author() {
    }

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    public Integer getId() {
        return id;
    }
    public void setId(Integer id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }

    @JsonManagedReference
    @Fetch(FetchMode.SELECT)
    @OneToMany(fetch = FetchType.EAGER,mappedBy = "author", cascade = CascadeType.ALL)
    public Set<Book> getBooks() {
        return books;
    }
    public void setBooks(Set<Book> books) {
        this.books = books;
    }
}

@Entity
@Table(name="books")
public class Book {
    private Integer id;
    private String book_name;
    private Author author;

    public Book() {
    }

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    public Integer getId() {
        return id;
    }
    public void setId(Integer id) {
        this.id = id;
    }

    public String getBook_name() {
        return book_name;
    }
    public void setBook_name(String book_name) {
        this.book_name = book_name;
    }

    @JsonBackReference
    @ManyToOne
    @JoinColumn(name = "author_id")
    public Author getAuthor() {
        return author;
    }
    public void setAuthor(Author author) {
        this.author = author;
    }
}