数据库表
用户表（User）
| id | username | password |
客户表（Customer），客户表id引用用户表id
| id | phone |
员工表（Employee），员工表id引用用户表id
| id |
飞机表（Plane），飞机表包含客机和战斗机，客机有厕所，战斗机有武器
| id | type | speed | wc_position | weapon_position |
实体映射
//子类共享属性id，version
@MappedSuperclass
public abstract class IdentifiedEntity implements Serializable {
@Id
@GeneratedValue
@Getter private Long id;
@Version
@Getter private int version;
private void setId(Long id) { this.id = id; }
private void setVersion(int version) { this.version = version; }
}
// User的id是在父类IdentifiedEntity中定义的
@Entity
public class User extends IdentifiedEntity {
@Getter @Setter private String username;
@Getter @Setter private String password;
}
// Customer，Employee是User的子类
// 它们的id既是主键也是外键
// 它们的主键都作为外键引用User表的主键
@Entity
@PrimaryKeyJoinColumn(name = "id")
public class Customer extends User {
@Getter @Setter private String phone;
}
@Entity
@PrimaryKeyJoinColumn(name = "id")
public class Employee extends User {
@Getter @Setter private String qq;
}
// Plane是A370和J10的父类
@Entity
@Inheritance(strategy=InheritanceType.SINGLE_TABLE)
@DiscriminatorColumn(name="type", discriminatorType=DiscriminatorType.STRING)
public class Plane extends IdentifiedEntity{
private String speed;
}
@Entity
@DiscriminatorValue("370")
public class A370 extends Plane{
private String wc_position;
}
@Entity
@DiscriminatorValue("738")
public class j10 extends Plane{
private String weapon_position;
}
时间： 2024-11-10 07:24:14