线程“main” org.hibernate.AnnotationException 中的异常：

Question

嗨，我刚刚创建了一个应用程序，该应用程序通过一对一映射保存表中的数据当我试图在表中保存数据时，我都会收到以下错误。`Exception in thread "main" org.hibernate.AnnotationException: @OneToOne or @ManyToOne on com.mapping.onetoone.Instructor.theInstructorDetail references an unknown entity: com.mapping.onetoone.InstructorDetail`这是我的代码与@Entity和一对一注释讲师.java@Id@GeneratedValue(strategy=GenerationType.IDENTITY)@Column(name="id")private int id;@Column(name="first_name")private String firstName;@Column(name="last_name")private String lastName;@Column(name="email")private String email;@OneToOne(cascade=CascadeType.ALL   )@JoinColumn(name="instructor_detail_id")private InstructorDetail theInstructorDetail;public Instructor(){}public Instructor(String firstName, String lastName, String email) {    super();    this.firstName = firstName;    this.lastName = lastName;    this.email = email;}public int getId() {    return id;}public void setId(int id) {    this.id = id;}public String getFirstName() {    return firstName;}public void setFirstName(String firstName) {    this.firstName = firstName;}public String getLastName() {    return lastName;}public void setLastName(String lastName) {    this.lastName = lastName;}public String getEmail() {    return email;}public void setEmail(String email) {    this.email = email;}public InstructorDetail getTheInstructorDetail() {    return theInstructorDetail;}public void setTheInstructorDetail(InstructorDetail theInstructorDetail) {    this.theInstructorDetail = theInstructorDetail;}@Overridepublic String toString() {    return "Instructor [id=" + id + ", firstName=" + firstName + ", lastName=" + lastName + ", email=" + email            + ", theInstructorDetail=" + theInstructorDetail + "]";}

Answer 1

一对一单向协会

您的代码设置指向“讲师详细信息”为父级，“教师”为子级关联。为此，您应该在保留/保存教师实体之前保留/保存 InstructorDetail。OneToOne Unidirectional Association

session.beginTransaction();

session.save(theInstructorDetail);

session.save(ins);

session.getTransaction().commit();

一对一双向协会

如果您不想在 DB 中关联 FK，请在 java 休眠中创建双向关联：

讲师.java

@OneToOne

 @JoinColumn(name = "instructor_detail_id")

 private InstructorDetail theInstructorDetail;

讲师详情.java

 @OneToOne(mappedBy="instructor_detail")

 private Instructor theInstructor;

持久逻辑

Instructor ins=new Instructor("elon", "musk", "[e-mail]");

InstructorDetail theInstructorDetail=new InstructorDetail("vella Panti Adda", "Acting");

ins.setTheInstructorDetail(theInstructorDetail);

theInstructorDetail.setTheInstructor(ins);

session.beginTransaction();

session.save(theInstructorDetail);

session.getTransaction().commit(); 

推荐结构

如果您可以对数据库进行更改，我建议您执行以下操作之一：

备选案文A）：更好

作为主表和辅助表，在逻辑上更有意义。也就是说，从表中删除列并在InsucateDetail表中添加列。然后，只需翻转java类中的休眠注释配置（与上述相反）。InstructorInstructorDetailinstructor_detail_idInstructorinstructor_id

选项 B）：最佳

由于它是一对一关系，因此若要减少内存上的索引占用空间，请对两个表使用相同的 PK。然后，您可以使用注释而不必使用。Instructor_Id@MapsIdBi-directional association

讲师详情.java

 @OneToOne

 @MapsId

 private Instructor theInstructor;

Answer 2

你已经试过了。

public Instructor(String firstName, String lastName, String email) {

    super();

    this.firstName = firstName;

    this.lastName = lastName;

    this.email = email;

    this.theInstructorDetail= new InstructorDetail();

}

我认为你应该开始所有的属性。