我有一个实体与Composote关键对以下表：1-用户2-部门
我使用Spring Data通过JpaRepository的save方法保存实体，现在如果我在同一个transaction中保存后更新实体，更新不会发生，这是通过在同一个@ transaction中使用setter方法更新字段来完成的。
这似乎是我保存的实体（新实体）是不管理.这是因为实体主键不是长/短？

**更新：**如果我使用从保存返回的实体它工作，我认为因为主键不是null，Spring会认为它是合并而不是持久化，因此用于保存的实体与返回的实体不一样。

@Entity
@Table(name = "user")
@Data
@Builder(toBuilder = true)
@NoArgsConstructor
@AllArgsConstructor
@ToString
public class User{

 @Id
  @GeneratedValue(strategy = GenerationType.IDENTITY)
  private Long id;

  private String username;

}

@Entity
@Table(name = "department")
@Data
@Builder
@NoArgsConstructor
@AllArgsConstructor
public class Department {

  @Id
  @GeneratedValue(strategy = GenerationType.IDENTITY)
  private Long id;
  private String name;
}

@Entity
@Table(name = "COURSE")
@Data
@Builder(toBuilder = true)
@NoArgsConstructor
@AllArgsConstructor
public class Course  {

  @EmbeddedId private CourseId courseId;
  
  private String name;
}


@Embeddable
@Data
@Builder(toBuilder = true)
@NoArgsConstructor
@AllArgsConstructor
public class CourseId implements Serializable {

  @ManyToOne
  @JoinColumn(name = "USER_ID")
  private User user;

  @ManyToOne
  @JoinColumn(name = "DEPARTMENT_ID")
  private Department department;
}

public interface CourseRepository  extends JpaRepository<Course, CourseId> {

}

@Transactional
public void createCourse(){
    
    User user=userRepository.findOneByName("user1");
    Department department=departmentRepository.findOneByName("department");
    CourseId courseId=new CourseId(user,department);
    Course course=new Course();
    course.setCourseId(courseId);
    courseRepository.save(course);// here it works
    course.setName("test"); // this doesn't update

}

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