POST / PUT / DELETE方法时，即使使用cascade = CascadeType.A

我正在尝试使用POST Rest API将新对象添加到h2内存数据库中。我收到此错误：嵌套异常是org.hibernate.exception.ConstraintViolationException

在我的费用实体中，我已经放置了@ManyToOne（cascade = CascadeType.ALL），所以在创建费用对象之前不应该创建类别对象，不是吗？

提前致谢。这是我的实体：公共课程费用{

@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
@Column(name = "id", updatable = false, nullable = false)
private Long id;
private String description;
@Column(name = "expense_date")
private Instant expenseDate;
@Column(name = "location")
private String location;
@ManyToOne(cascade={CascadeType.ALL})
@Nullable
@JoinColumn(name = "category_id", referencedColumnName = "id", nullable = false)
private Category category;
@ManyToOne(cascade=CascadeType.ALL)
@JoinColumn(name = "user_id", referencedColumnName = "id", nullable = false)
@Nullable
@JsonIgnore
private User user;}

类别类别公共类别类别{

@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
@Column(name = "id", updatable = false, nullable = false)
private Long id;
@NonNull
private String name;}

用户类别：公共类别用户{

@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
@Column(name = "id", updatable = false, nullable = false)
private Long id;
private String name;
private String email;}