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java - 保存单向一对一子实体时分离的持久化父实体

问题描述

我正在使用 spring boot 为我的第一个应用程序编写一些测试。我使用@MapsId 在用户和老师之间创建了一个单向关系，以便用户和老师的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。尽管以某种方式将老师（新实体）与耦合用户（保留在数据库中）一起保存时，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;

}

并且用户实体没有引用教师类：

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

在我的测试中，我首先创建了一个用户：

@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());
}

教师服务如下所示：

@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);
    }

}

现在在返回线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

标签： javahibernatejpa

解决方案

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性处于不同的事务中。在读取和写入之间，它会分离。将一个 @Transactional 注释放在顶部或手动确保事务性，它将起作用。

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