Spring POST错误与第三实体关系

Posted 2023-02-04

我是Spring的新手，我想通过这种结构存储考试和问题之间的关系：

@Entity
@Data
@EqualsAndHashCode(callSuper = true)
public class Exam extends UriEntity<Integer> 

  @Id
  @GeneratedValue(strategy = GenerationType.IDENTITY)
  private Integer id;

  @NotBlank
  @Length(min = 1, max = 256)
  private String name;

  @OneToMany(mappedBy="exam")
  private List<ExamQuestion> exams_questions;

@Entity
@Data
@EqualsAndHashCode(callSuper = true)
public class Question extends UriEntity<Integer> 

  @Id
  @GeneratedValue(strategy = GenerationType.IDENTITY)
  private Integer id;

  @NotBlank
  @Column(unique = true)
  private String statement;

  @NotBlank
  private String answer;

  @OneToMany(mappedBy="question")
  private List<ExamQuestion> exams_questions;

@Entity
@Data
@EqualsAndHashCode(callSuper = true)
public class ExamQuestion extends UriEntity<Integer> 

  @Id
  @GeneratedValue(strategy = GenerationType.IDENTITY)
  private Integer id;

  @ManyToOne
  @JoinColumn(name = "question_id")
  private Question question;

  @ManyToOne
  @JoinColumn(name = "exam_id")
  private Exam exam;

[当我想用POSTMAN存储新的ExamQuestion对象时

  "exam": "http://localhost:8080/exams/28",
  "question": "http://localhost:8080/questions/17"

我收到错误409，并且消息：

列\“ ID \”不允许为NULL；

有谁可以帮助我？预先感谢。

答案

可能由于@GeneratedValue(strategy = GenerationType.IDENTITY)而发生。