java.sql.SQLIntegrityConstraintViolationException：

Question

我在休眠中建立了一对多的关系，但是当我尝试在表中插入一个值时，我得到了我的照片实体中的 FK 不能为空的异常。

我的父实体：

@Table(name = "library")

@Entity

public class Book {

@OneToMany(

        fetch = FetchType.LAZY,

        mappedBy = "book",

        cascade = CascadeType.ALL,

        orphanRemoval = true

)

// setters / getters and other columns 

我的子实体

@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 null

com.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 对象和控制器：

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";}

Answer 1

很可能您还没有设置从 Photo 到 Book 的反向引用，然后您通过 photoes 集合从 Book 级联持久/合并操作。当您将元素添加到集合时，您需要维护关系的双方。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.