如何在 Spring 引导中扩展 class 而不更改 MySQL 架构？

Question

例如，我有用户 class，如下所示：

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

        @NotBlank
        @Size(max = 40)
        @Column(name = "name")
        private String name;

        @NotBlank
        @Size(max = 15)
        @Column(name = "username")
        private String username;

        @NaturalId
        @NotBlank
        @Size(max = 40)
        @Email
        @Column(name = "email")
        private String email;

        @NotBlank
        @Size(max = 100)
        @Column(name = "password")
        private String password;

        @ManyToMany(fetch = FetchType.LAZY)
        @JoinTable(name = "user_roles",
                joinColumns = @JoinColumn(name = "user_id"),
                inverseJoinColumns = @JoinColumn(name = "role_id"))
        private Set<Role> roles = new HashSet<>();

//Constructor
//Getters and Setters

我有客户 class：

@Entity
@Table(name = "cliente")
public class Cliente {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Column(name = "id")
    private Long id;
    @Column(name = "empresa")
    private String empresa;
    @Column(name = "telefono")
    private Integer telefono;

    @OneToOne(cascade = CascadeType.ALL)
    @JoinColumn(unique = true)
    private Licencia licencia;

    @OneToMany(cascade = {
            CascadeType.PERSIST,
            CascadeType.REMOVE
    } ,fetch = FetchType.EAGER)
    @JoinTable(name = "user_cliente",
            joinColumns = @JoinColumn(name = "cliente_id"),
            inverseJoinColumns = @JoinColumn(name = "user_id"))
    private Set<User> users = new HashSet<>();

    public Cliente(String empresa, Integer telefono) {
        this.empresa = empresa;
        this.telefono = telefono;
    }

//Constructor
//Getters and Setters

Now, what I want to do is the Client class to extends the User class, so I can add a Client with name, username, email, etc. But I want two separate tables in MySQL, one for the users and its attributes, and其他只为客户提供客户信息，如电话或公司。 问题是当我在客户端 class 中扩展用户 class 时，MySQL 数据库更新并在用户表中创建电话、公司等字段。 我怎样才能避免这种情况？

Answer 1

使用@MappedSuperclass ：

@MappedSuperclass
public class BaseEntity {
    // here you can add common fields for your entities
}

然后从它扩展：

@Entity
public class User extends BaseEntity {
    // user specific fields goes here
}

和Client ：

@Entity
@Table(name = "cliente")
public class Cliente extends BaseEntity {
    // client specific fields here
}

有关更多信息，请阅读如何使用带有 JPA 和 Hibernate 的 @MappedSuperclass 从基本 class 实体继承属性