如何使用cascade.all双向

Question

我想要做的是当我保存School对象时，我还想在数据库中保存（或更新）学生。如果学生得到更新，那么城市也必须更新。

class Student{

  @JoinColumn(....)
  @ManyToOne(cascade = CascadeType.ALL, optional = false, fetch = FetchType.EAGER)
  private School school;

  @JoinColumn(....)
  @ManyToOne(cascade = CascadeType.ALL, optional = false, fetch = FetchType.EAGER)
  private City city;

}


class School{

  @OneToMany(cascade = CascadeType.ALL, mappedBy = "....", fetch=fetchType.LAZY)
  private List<Student> studentList;

}

Answer 1

class Student{

  @ManyToOne
  private School school;

  @ManyToOne(cascade = CascadeType.MERGE)
  private City city;

}


class School{

  @OneToMany(cascade = {CascadeType.PERSIST,CascadeType.MERGE})
  private List<Student> studentList;

}