在JPA中，实体的继承策略定义了如何将继承关系映射到数据库中的表结构。常见的继承策略包括Single Table（单表继承）、Joined（连接表继承）和Table Per Class（每个类对应一个表）。
1. Single Table（单表继承）
所有子类共享一个数据库表，使用一个类型字段来区分不同的子类。
@Entity
@Inheritance(strategy = InheritanceType.SINGLE_TABLE)
@DiscriminatorColumn(name = "employee_type", discriminatorType = DiscriminatorType.STRING)
public class Employee {
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
private Long id;
private String name;
}
@Entity
@DiscriminatorValue("manager")
public class Manager extends Employee {
private String department;
}
@Entity
@DiscriminatorValue("developer")
public class Developer extends Employee {
private String programmingLanguage;
}
2. Joined（连接表继承）
每个类对应一个数据库表，子类表通过外键与父类表关联。
@Entity
@Inheritance(strategy = InheritanceType.JOINED)
public class Employee {
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
private Long id;
private String name;
}
@Entity
public class Manager extends Employee {
private String department;
}
@Entity
public class Developer extends Employee {
private String programmingLanguage;
}
3. Table Per Class（每个类对应一个表）
每个类都有自己的数据库表，包含父类和子类的所有属性。
@Entity
@Inheritance(strategy = InheritanceType.TABLE_PER_CLASS)
public class Employee {
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
private Long id;
private String name;
}
@Entity
public class Manager extends Employee {
private String department;
}
@Entity
public class Developer extends Employee {
private String programmingLanguage;
}
原文链接: https://blog.csdn.net/2401_82884096/article/details/137016244