其中一个解决方案是在 ToDo 实体及相关 ToDoTask 实体类型。

@Entity
@Inheritance(strategy = InheritanceType.TABLE_PER_CLASS)
@DiscriminatorColumn(name = "TYPE")
public class Task {
  @Id
  @GeneratedValue
  private Integer id;
  @ManyToOne
  private TaskList taskList;
  @Column(name = "TYPE", insertable = false, updatable = false, nullable = false)
  private String type;
}

@Entity
@DiscriminatorValue("TYPE1")
public class SubTaskType1 extends Task {}

@Entity
@DiscriminatorValue("TYPE2")
public class SubTaskType2 extends Task {}

@Entity
public class ToDoList {
  @Id
  @GeneratedValue
  private Integer id;
  @OneToMany(mappedBy = "taskList")
  private List<Task> tasks;
}

你的代码应该变成：

ToDoList todos = todoRepository.findById( todoId );
for ( Task task : todos.getTasks() ) {
  // access task.getType() to get the discriminator type 
  // or
  // use instanceof to handle subclass casting
}