我有两个具有@ManyToOne关系的实体类，如下所示。

@Entity
public class Student {

  @Id
  private Integer studentId;

  @Column(nullable = false)
  private String studentName;

  @ManyToOne(targetEntity = School.class, fetch = FetchType.LAZY, optional = false)
  @JoinColumn(referencedColumnName = "schoolId", insertable = false, updatable = false)
  private School school;

  //Getters and Setters methods

。

@Entity
public class School {
  @Id
  @GeneratedValue(strategy = GenerationType.AUTO)
  private Integer schoolId;

  @Column(nullable = false)
  private String schoolName;

  //Getters and Setters methods

当我尝试使用CrudRepository默认方法studentRepository.save(student)和JSON有效负载保存学生对象时，它给了我一个错误java.sql.SQLException: Field 'school_id' doesn't have a default value。当我在调试模式下运行时，我可以看到School对象被正确设置。
我的JSON有效负载如下：

[
    {
      "studentId": "2015020",
      "studentName": "ABC",
      "school": {
        "schoolId": 1
      }
    }
]

我是SpringDataJPA的新手，所以这可能是一个非常基本的错误。