洗掉具有許多關系的物體時，非空屬性參考空值或瞬態值

我有 AppUser 可以有很多 BookCards，它可以有很多書。我需要用他的 BookCards 物體洗掉我的 AppUser，但書本身沒有任何變化。但是當我嘗試通過這種方法做到這一點時

@Transactional
    public void deleteUser(Long id) {
        List<BookCard> bookCards = bookCardService.findAllUserBookCards(id);

        if (!bookCards.isEmpty()) {
            bookCardService.deleteBookCardByUserId(id);
        }

        userRepository.deleteById(id);
    }

我有一個錯誤

org.hibernate.PropertyValueException: not-null property references a null or transient value : kpi.diploma.ovcharenko.entity.card.BookCard.book

這是我的 AppUser、Book 和 BookCard 類

@Getter
@Setter
@Entity
@NoArgsConstructor
@AllArgsConstructor
@Builder(toBuilder = true)
@Table(uniqueConstraints = @UniqueConstraint(columnNames = "email"), name = "library_user")
public class AppUser {
    @Id
    @Column(name = "id")
    @GeneratedValue(strategy = GenerationType.AUTO)
    private Long id;

    // other fields 

    @EqualsAndHashCode.Exclude
    @OnDelete(action = OnDeleteAction.CASCADE)
    @OneToMany(mappedBy = "book", fetch = FetchType.EAGER)
    private Set<BookCard> bookCards = new HashSet<>();

    // getters and setters

@Getter
@Setter
@Entity
@NoArgsConstructor
@AllArgsConstructor
@Builder(toBuilder = true)
@Table(name = "booking_card")
@TypeDef(
        name = "pgsql_enum",
        typeClass = PostgreSQLEnumType.class
)
public class BookCard {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Column(name = "id")
    private Long id;

    @ManyToOne(cascade = CascadeType.ALL, fetch = FetchType.EAGER)
    @OnDelete(action = OnDeleteAction.CASCADE)
    @JoinColumn(name = "user_id", nullable = false)
    private AppUser user;

    @OnDelete(action = OnDeleteAction.NO_ACTION)
    @ManyToOne(cascade = CascadeType.ALL, fetch = FetchType.EAGER, optional = false)
    @JoinColumn(name = "book_id")
    private Book book;

    // getters and setters

@Getter
@Setter
@Entity
@NoArgsConstructor
@AllArgsConstructor
@Builder(toBuilder = true)
@Table(name = "books")
public class Book {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Column(name = "idbooks", insertable = false, updatable = false)
    private Long id;

    // other fields 

    @EqualsAndHashCode.Exclude
    @OnDelete(action = OnDeleteAction.NO_ACTION)
    @OneToMany(mappedBy = "book", fetch = FetchType.EAGER)
    private Set<BookCard> bookCards = new HashSet<>();
    
    // getters and setters

如您所見，我的 Book 類具有 Set bookCards 欄位，只是為了低估我嘗試添加許多注釋，例如@OnDelete(action = OnDeleteAction.CASCADE)，相信它們可以解決我的問題

據我了解，洗掉 AppUser 和他的 BookCard 沒有問題，但是因為 BookCard 與 Book 有關系，所以 hibernate 不明白如何處理 Book。那么我怎樣才能讓我的程式清楚地知道我只需要洗掉 BookCards 物體，但不要碰書本身呢？非常感謝

uj5u.com熱心網友回復：

對于可能面臨類似錯誤的未來讀者。我解決了像這樣更改物體的問題

@Getter
@Setter
@Entity
@NoArgsConstructor
@AllArgsConstructor
@Builder(toBuilder = true)
@Table(uniqueConstraints = @UniqueConstraint(columnNames = "email"), name = "library_user")
public class AppUser {
    @Id
    @Column(name = "id")
    @GeneratedValue(strategy = GenerationType.AUTO)
    private Long id;

    // other fields 

    @EqualsAndHashCode.Exclude
    @OnDelete(action = OnDeleteAction.CASCADE)
    @OneToMany(mappedBy = "user", fetch = FetchType.EAGER, cascade = CascadeType.ALL)
    private Set<BookCard> bookCards = new HashSet<>();

    // getters and setters

@Getter
@Setter
@Entity
@NoArgsConstructor
@AllArgsConstructor
@Builder(toBuilder = true)
@Table(name = "booking_card")
@TypeDef(
        name = "pgsql_enum",
        typeClass = PostgreSQLEnumType.class
)
public class BookCard {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Column(name = "id")
    private Long id;

    @ManyToOne(cascade = CascadeType.REFRESH, fetch = FetchType.EAGER)
    @JoinColumn(name = "user_id", nullable = false)
    private AppUser user;

    @ManyToOne(cascade = CascadeType.REFRESH, fetch = FetchType.EAGER)
    @JoinColumn(name = "book_id")
    private Book book;

    // getters and setters

@Getter
@Setter
@Entity
@NoArgsConstructor
@AllArgsConstructor
@Builder(toBuilder = true)
@Table(name = "books")
public class Book {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Column(name = "idbooks", insertable = false, updatable = false)
    private Long id;

    // other fields 

    @EqualsAndHashCode.Exclude
    @OnDelete(action = OnDeleteAction.CASCADE)
    @OneToMany(mappedBy = "user", fetch = FetchType.EAGER, cascade = CascadeType.ALL)
    private Set<BookCard> bookCards = new HashSet<>();
    
    // getters and setters

這個注解解決了這個問題 org.hibernate.PropertyValueException: not-null property references a null or transient value : kpi.diploma.ovcharenko.entity.card.BookCard.book

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