保存单向一对一子实体时分离的固定父实体

Question

我正在使用 Spring boot 为我的第一个应用程序编写一些测试。我利用@MapsId在用户和教师之间创建了一个单一关系，以便用户和教师的 pks 相同。现在我认为由于关系仅在教师部分指定，因此在调用保存操作时不会保存用户。尽管不知何故，当使用耦合用户(保留在数据库中(保存教师(新实体(时，我得到了一个分离的实体异常。实体的相关部分如下所示：

@Entity
public class Teacher {
@Id
private Long id;
@OneToOne(fetch = FetchType.LAZY)
@MapsId
private User user;
}

并且用户实体没有对教师类的引用：

@Entity
public class User {
// some fields getters and setters
}

在我的测试中，我首先创建一个用户：

@Test doSomeUserOperations() {
User user = new User()
// set some user info
userRepository.save(user)
// next i want to couple a teacher entity via a method in the teacher service
Teacher teacher = teacherService.getAndCreateTeacherForUser(user.getId());
}

老师服务如下所示：

@Service
public class TeacherService {
@Autowired TeacherRepository teacherRepo; (both extending JpaRepo)
@Autowired UserRepository userRepo;
public Teacher getAndCreateTeacherForUser(Long userId) {
Teacher newTeacher = new Teacher();
newTeacher.setUser(userRepo.findById(userId).get());
return teacherRepo.save(newTeacher);
}
}

现在在返回行上，我得到以下异常跟踪：

org.springframework.dao.InvalidDataAccessApiUsageException: detached entity passed to persist: com.dorresteijn.wordteacher.model.User; nested exception is org.hibernate.PersistentObjectException: detached entity passed to persist: com.dorresteijn.wordteacher.model.User
at org.springframework.orm.jpa.vendor.HibernateJpaDialect.convertHibernateAccessException(HibernateJpaDialect.java:280)
at org.springframework.orm.jpa.vendor.HibernateJpaDialect.translateExceptionIfPossible(HibernateJpaDialect.java:225)
at org.springframework.orm.jpa.AbstractEntityManagerFactoryBean.translateExceptionIfPossible(AbstractEntityManagerFactoryBean.java:527)
at org.springframework.dao.support.ChainedPersistenceExceptionTranslator.translateExceptionIfPossible(ChainedPersistenceExceptionTranslator.java:61)
at org.springframework.dao.support.DataAccessUtils.translateIfNecessary(DataAccessUtils.java:242)
at org.springframework.dao.support.PersistenceExceptionTranslationInterceptor.invoke(PersistenceExceptionTranslationInterceptor.java:153)
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:185)
at org.springframework.data.jpa.repository.support.CrudMethodMetadataPostProcessor$CrudMethodMetadataPopulatingMethodInterceptor.invoke(CrudMethodMetadataPostProcessor.java:135)
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:185)
at org.springframework.aop.interceptor.ExposeInvocationInterceptor.invoke(ExposeInvocationInterceptor.java:92)
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:185)
at org.springframework.data.repository.core.support.SurroundingTransactionDetectorMethodInterceptor.invoke(SurroundingTransactionDetectorMethodInterceptor.java:61)
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:185)
at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:212)
at com.sun.proxy.$Proxy154.save(Unknown Source)
at 

Answer 1

答案很简单。您的服务不是事务性的，因此用户的读取与教师的持久处于不同的事务中。在读取和写入之间，它被分离。将一个@Transactional注释放在顶部或手动确保事务性，它将起作用。

Answer 2

这可能是合并逻辑的问题，我认为在这种情况下save用于创建新对象，如果层次结构具有已经保存的object，它会抱怨。在这种情况下，您应该使用saveOrUpdate，而不是save.