在我的单元测试中,我收到JpaSystemException:此类的 ids 必须在调用 save() 之前手动分配错误
。我重新措辞了我的实体,使问题更短、更具可读性。
因此学生与表 EnrolledInfo 具有可选的一对一关系。
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)
我当然不必在保存学生实体之前保存已注册信息实体吗?
@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():
}
最佳答案
您的EnrolledInfo将studentId作为其ID,并且没有生成策略,因为它的ID来自关系,因为它是其父ID(学生)。为此,在保存过程中必须了解学生。
所以EnrolledInfo必须知道它的学生,jpa本身不处理双方关系,所以可以手动设置。
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,因此没有理由使用旧映射,但以防万一):
@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;
关于java - Hibernate 一对一单向 - id 未分配,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/29370292/