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休眠一对一单向-未分配ID

one-to-one hibernate spring java

1

Robbo_UK · 技术社区 · 11 年前

在我的单元测试中 JpaSystemException: ids for this class must be manually assigned before calling save() error 。我已重新编写了我的实体,使问题更简短、更易读。

因此,学生与EnrolledInfo表有一个可选的一对一关系。

学生实体

@Entity
@Table(name = "Student")
public class Student  {

    @Id
    @Column(name = "studentId")
    @GeneratedValue(strategy = GenerationType.AUTO)
    private Long studentId;

    @OneToOne(fetch = FetchType.LAZY, mappedBy = "student", cascade = CascadeType.ALL)
    private EnrolledInfo enrolledInfo;

    private String firstName;

    private String lastName;

    // setters&getters etc..    
}

EnrolledInfo实体

@Entity
@Table(name = "EnrolledInfo")
public class EnrolledInfo implements Serializable {

    @Id
    private Long studentId;

    @OneToOne(fetch = FetchType.Eager)
    @PrimaryKeyJoinColumn
    @JsonBackReference
    private Student student;

    @Column(name = "enrolledDate")
    private Date enrolledDate;

    @Column(name = "paidTuition")
    private Boolean paidTuition;

    // setters&getters etc..
}

将其放在一起进行测试(此错误)

在保存学生信息之前,我肯定不必保存已注册的信息实体吗?

@Test
public void student_test() {

  Student student = new Student();
  EnrolledInfo enrolledInfo = new EnrolledInfo(); 
  enrolledInfo.setPaidTuition(true);

  student.setEnrolledInfo(enrolledInfo);        
  studentDao.save(student);
  // errors on // JpaSystemException: ids for this class must be manually assigned before calling save():
}

1 回复 | 直到 11 年前

1

Zielu 11 年前

您的EnrolledInfo将studentId作为其Id,没有生成策略,因为它的Id来自关系,因为它是其父Id(学生)。要使其工作,必须在保存期间了解该学生。

因此,EnrolledInfo必须了解其学生,jpa本身不处理关系的双方,因此可以手动设置。

  Student student = new Student();
  EnrolledInfo enrolledInfo = new EnrolledInfo(); 
  enrolledInfo.setPaidTuition(true);
  enrolledInfo.setStudent(student);

  student.setEnrolledInfo(enrolledInfo);        
  studentDao.save(student);

现在在JPA2中,正确的注释应该是:

@Entity
@Table(name = "EnrolledInfo")
public class EnrolledInfo implements Serializable {

    @Id
    private Long studentId;

    @OneToOne(fetch = FetchType.Eager)
    @Id
    @JsonBackReference
    private Student student;

在带有@PrimaryKeyJoinColumn的JPA1中,您需要提供完整的映射(您现在应该使用JPA2,所以没有理由使用旧的映射,只是以防万一):

@Entity
@Table(name = "EnrolledInfo")
public class EnrolledInfo implements Serializable {

    @Id
    @Column(name="STUDENT_ID")
    private Long studentId;

    @OneToOne(fetch = FetchType.Eager)
    @PrimaryKeyJoinColumn(name="STUDENT_ID", referencedColumnName="STUDENT_ID")
    @JsonBackReference
    private Student student;