相关疑难解决方法(0)

我遇到过一种情况(我觉得很奇怪,但可能很正常),我使用EntityManager.getReference(LObj.getClass(),LObj.getId())获取数据库实体,然后将返回的对象传递给坚持在另一张桌子上.

所以基本上流程是这样的:

class TFacade{

  createT(FObj, AObj) {
    T TObj = new T();
    TObj.setF(FObj);
    TObj.setA(AObj);
    ...
    EntityManager.persist(TObj);
    ...
    L LObj = A.getL();
    FObj.setL(LObj);
    FFacade.editF(FObj);
  }
}

@TransactionAttributeType.REQUIRES_NEW
class FFacade{

  editF(FObj){
    L LObj = FObj.getL();
    LObj = EntityManager.getReference(LObj.getClass(), LObj.getId());
    ...
    EntityManager.merge(FObj);
    ...
    FLHFacade.create(FObj, LObj);
  }
}

@TransactionAttributeType.REQUIRED
class FLHFacade{

  createFLH(FObj, LObj){
    FLH FLHObj = new FLH();
    FLHObj.setF(FObj);
    FLHObj.setL(LObj);
    ....
    EntityManager.persist(FLHObj);
    ...
  }
}

我得到以下异常"java.lang.IllegalArgumentException:未知实体:com.my.persistence.L $$ EnhancerByCGLIB $$ 3e7987d0"

在查看了一段时间之后,我终于想通了,因为我正在使用EntityManager.getReference()方法,因为该方法正在返回代理,所以我得到了上述异常.

这让我想知道,何时建议使用EntityManager.getReference()方法而不是EntityManager.find()方法？

如果EntityManager.getReference()无法找到正在搜索的实体本身非常方便,则会抛出EntityNotFoundException.如果EntityManager.find()方法无法找到实体,则它仅返回null.

关于事务边界,听起来像你需要在将新发现的实体传递给新事务之前使用find()方法.如果你使用getReference()方法,那么你可能会遇到类似我的情况,但有上述异常.

在我的spring项目的自定义AuthenticationProvider中,我正在尝试读取已登录用户的权限列表,但我遇到以下错误:

org.hibernate.LazyInitializationException: failed to lazily initialize a collection of role: com.horariolivre.entity.Usuario.autorizacoes, could not initialize proxy - no Session
    at org.hibernate.collection.internal.AbstractPersistentCollection.throwLazyInitializationException(AbstractPersistentCollection.java:566)
    at org.hibernate.collection.internal.AbstractPersistentCollection.withTemporarySessionIfNeeded(AbstractPersistentCollection.java:186)
    at org.hibernate.collection.internal.AbstractPersistentCollection.initialize(AbstractPersistentCollection.java:545)
    at org.hibernate.collection.internal.AbstractPersistentCollection.read(AbstractPersistentCollection.java:124)
    at org.hibernate.collection.internal.PersistentBag.iterator(PersistentBag.java:266)
    at com.horariolivre.security.CustomAuthenticationProvider.authenticate(CustomAuthenticationProvider.java:45)
    at org.springframework.security.authentication.ProviderManager.authenticate(ProviderManager.java:156)
    at org.springframework.security.authentication.ProviderManager.authenticate(ProviderManager.java:177)
    at org.springframework.security.web.authentication.UsernamePasswordAuthenticationFilter.attemptAuthentication(UsernamePasswordAuthenticationFilter.java:94)
    at org.springframework.security.web.authentication.AbstractAuthenticationProcessingFilter.doFilter(AbstractAuthenticationProcessingFilter.java:211)
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342)
    at org.springframework.security.web.authentication.logout.LogoutFilter.doFilter(LogoutFilter.java:110)
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342)
    at org.springframework.security.web.header.HeaderWriterFilter.doFilterInternal(HeaderWriterFilter.java:57)
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342)
    at org.springframework.security.web.context.SecurityContextPersistenceFilter.doFilter(SecurityContextPersistenceFilter.java:87)
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342)
    at org.springframework.security.web.context.request.async.WebAsyncManagerIntegrationFilter.doFilterInternal(WebAsyncManagerIntegrationFilter.java:50)
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342)
    at org.springframework.security.web.FilterChainProxy.doFilterInternal(FilterChainProxy.java:192)
    at org.springframework.security.web.FilterChainProxy.doFilter(FilterChainProxy.java:160)
    at org.springframework.web.filter.DelegatingFilterProxy.invokeDelegate(DelegatingFilterProxy.java:343)
    at org.springframework.web.filter.DelegatingFilterProxy.doFilter(DelegatingFilterProxy.java:260)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:243)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:222)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:123)
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:502)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:171) …

我读到这getOne()是懒惰加载并立即findOne()获取整个实体.我检查调试日志,我甚至能监视我的SQL服务器上看到被执行什么语句,我发现,无论getOne()和findOne()生成和执行相同的查询.但是当我使用时,getOne()这些值最初为null(当然除了id).

那么有人可以告诉我,如果两种方法在数据库上执行相同的查询,为什么我要使用一个而不是另一个？我基本上是在寻找一种获取实体的方法,而不会获得它的所有子/属性.

EDIT1:

实体代码

道码:

@Repository
public interface FlightDao extends JpaRepository<Flight, Long> {
}

调试日志findOne()vs getOne()

EDIT2:

感谢Chlebik,我能够找出问题所在.像Chlebik所说,如果你试图访问由getOne()完整查询提取的实体的任何属性将被执行.在我的情况下,我在调试时检查行为,一次移动一行,我完全忘记了调试IDE时尝试访问对象属性以进行调试(或者至少是我认为正在发生的事情),所以调试触发器完整的查询执行.我停止调试,然后检查日志,一切似乎都正常.

getOne()vs findOne()(这个日志来自MySQL general_log而不是休眠.

调试日志

没有调试日志

我使用spring数据jpa,这是我的样本:

public interface UserRepository extends JpaRepository<User, Long> {

    User findByUserName(String userName);
....}

@RunWith(SpringRunner.class)
@SpringBootTest
public class UserRepositoryTests {

    @Autowired
    private UserRepository userRepository;
    @Test
    public void test1(){
        String name = userRepository.getOne(3L).getUserName();
    }

}
@Entity
public class User extends Entitys implements Serializable {

    private static final long serialVersionUID = 1L;
    @Id
    @GeneratedValue
    private Integer id;
    @Column(nullable = false, unique = true)
    private String userName;
..}

test1将抛出"LazyInitializationException:无法初始化代理 - 无会话",但如果我使用userRepository.findByUserName("aa").getUserName()就可以了.虽然问题可以通过添加@Transactional来解决,但我想知道其背后的原因和原因.
我在/sf/answers/2406965361/中找到了anwser的一部分,但是findByUserName中的事务如何工作？