如何创建一张表的多个映射？ (jpa 休眠)

Question

我在 spring 引导中创建应用程序。 我希望一张表有多个实体映射。 一个实体在没有任何连接的情况下检索表，而另一个实体通过连接检索表。

这是表架构：

书： {"id":1, "title":"math1", "author_id":1}

作者： {"id":1, "name": "james"}

谢谢你。

Answer 1

我做到了。

@MappedSuperclass
public abstract class BookBase<T extends BookBase> {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Column(unique = true, nullable = false, updatable = false, name = "id")
    private Integer id;

    @Column(name = "title")
    private String title;

    public Integer getId() {
        return this.id;
    }

    public T setId(Integer id) {
        this.id = id;
        return (T) this;
    }

    public String getTitle() {
        return this.title;
    }

    public T setTitle(String title) {
        this. title = title
        return (T) this;
    }
}

@Entity
@Table
public class Book extends BookBase<Book> {
    @Column(name = "author_id")
    private Integer authorId;

    public Integer getAuthorId() {
        return authorId;
    }

    public void setAuthorId(Integer authorId) {
        this.authorId = authorId;
    }
}

@Entity
@Table
public class BookJoinAuthor extends BookBase<BookJoinAuthor> {
    @OneToOne(cascade = CascadeType.ALL)
    @JoinColumn(name = "author_id")
    private Author author;

    public Author getAuthor() {
        return author;
    }

    public void setAuthorId(Author author) {
        this.author = author;
    }
}

@Entity
@Table
public abstract class Author {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Column(unique = true, nullable = false, updatable = false, name = "id")
    private Integer id;

    @Column(name = "name")
    private String name;

    public Integer getId() {
        return this.id;
    }

    public T setId(Integer id) {
        this.id = id;
        return (T) this;
    }

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

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