我在休眠中建立了一對多的關系，但是當我嘗試在表中插入一個值時，我得到了我的照片實體中的 FK 不能為空的異常。我的父實體：@Table(name = "library")@Entitypublic class Book {@OneToMany( fetch = FetchType.LAZY, mappedBy = "book", cascade = CascadeType.ALL, orphanRemoval = true)// setters / getters and other columns 我的子實體@Entity@Table(name = "photos")public class photos{@Id@GeneratedValue(strategy = GenerationType.AUTO)@Column(name = "idphotos")private int id;@ManyToOne(cascade = CascadeType.ALL,fetch = FetchType.LAZY)@JoinColumn(name = "library_idlibrary")private Book book;// other columns 例外：java.sql.SQLIntegrityConstraintViolationException: Column 'library_idlibrary' cannot be nullcom.mysql.cj.jdbc.exceptions.SQLError.createSQLException(SQLError.java:115)com.mysql.cj.jdbc.exceptions.SQLError.createSQLException(SQLError.java:95)com.mysql.cj.jdbc.exceptions.SQLExceptionsMapping.translateException(SQLExceptionsMapping.java:122)com.mysql.cj.jdbc.ClientPreparedStatement.executeInternal(ClientPreparedStatement.java:960)com.mysql.cj.jdbc.ClientPreparedStatement.executeUpdateInternal(ClientPreparedStatement.java:1116)com.mysql.cj.jdbc.ClientPreparedStatement.executeUpdateInternal(ClientPreparedStatement.java:1066)我有插入值的 DAO 對象和控制器：控制器： @PostMapping( value = "/newBook",consumes = {MediaType.MULTIPART_FORM_DATA_VALUE})public String add(@ModelAttribute("book") @Valid Book book, HttpServletResponse response, HttpServletRequest request,@RequestParam(value = "photo", required = false) List<MultipartFile> photos, @RequestParam(value = "valute",required = false) String valute,BindingResult result) { if (result.hasErrors()) { return "addBook";}
1 回答
忽然笑
TA貢獻1806條經驗 獲得超5個贊
很可能您還沒有設置從 Photo 到 Book 的反向引用，然后您通過 photoes 集合從 Book 級聯持久/合并操作。當您將元素添加到集合時，您需要維護關系的雙方。例如：
Book book = new Book();
Photo photo = new Photo();
book.addPhoto(photo);
photo.setBook(book);
//notice on the line above we set the backreference of the photo to the book.
hibernateSession.persist(book);
// now it is cascading from book to photo and it will set the foreign keys correctly.
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