休眠一对一单向 - 未分配 ID

Question

在我的单元测试中，我得到 JpaSystemException: ids for this class must be manually assigned before calling save() error。我改写了我的实体，使问题更短、更易读。

因此学生与 table 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..
}

把它放在一起测试（这个错误）

在保存学生之前我真的不需要保存 enrolledInfo 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():
}

Answer 1

您的 EnrolledInfo 将 studentId 作为其 Id，并且没有生成策略导致其 id 来自关系，因为它是其父 id（学生）。为此，必须在保存期间知道学生。

所以EnrolledInfo必须知道它的student，jpa本身不处理关系的两边，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的，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;

休眠一对一单向 - 未分配 ID

Hibernate one to one unidirectional - ids not assigned

java

spring

hibernate

one-to-one