如何在 Spring 引导中加入 SQL 表？

Question

如何将 class 作者的 author_firstName 和 author_lastName 绑定到 class 本书？我使用 h2 数据库，author_id 和 book_id 是主键，我使用 postman

public class Book {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Column(name = "book_id")
    private int id;
    @Column(name = "book_title")
    private String title;
    @Column(name = "book_genre")
    private String genre;
    @Column(name = "author")
    private String author;

}

@Entity
@Table(name="Author")
@Data
@AllArgsConstructor
@NoArgsConstructor
public class Author {
    @Id
    @GeneratedValue(strategy=GenerationType.IDENTITY)
    @Column(name="author_id")
    private int authorId;
    
    @Column(name="author_firstName")
    private String firstName;
    
    @Column(name="author_lastName")
    private String lastName;
    @Column(name="author_birth")
    private Date birth;

}

Answer 1

不是将字符串参数用于 author，您应该将其转换为 @ManyToOne 关系：

@Entity
@Table(name="Author")
@Data
@AllArgsConstructor
@NoArgsConstructor
public class Author {
    @Id
    @GeneratedValue(strategy=GenerationType.IDENTITY)
    @Column(name="author_id")
    private int authorId;
    
    @Column(name="author_firstName")
    private String firstName;
    
    @Column(name="author_lastName")
    private String lastName;
    @Column(name="author_birth")
    private Date birth;

    @OneToMany(mappedBy = "author")
    private List<Book> books;

}

@Entity
public class Book {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Column(name = "book_id")
    private int id;
    @Column(name = "book_title")
    private String title;
    @Column(name = "book_genre")
    private String genre;

    @ManyToOne
    @JoinColumn(name = "author_id")
    private Author author;

}

使用此模型，您将能够从任何入口点、作者的书籍（特定作者撰写的书籍）或拥有书籍的作者（作者撰写的书籍集合）获取数据。

您可以使用 findAll Spring 数据 JPA 实现的默认实现（如果您使用 EAGER 提取类型，将自动连接两个表），或者构建您自己的 JPQL：

FROM Author a FETCH JOIN a.books b WHERE a.id = b.author.

这将有助于代码的易读性并提高数据库数据的规范化。

如何在 Spring 引导中加入 SQL 表？

How to join SQL tables in Spring Boot?

java

spring

h2