删除ManyToOne记录后发生Spring Data JPA JpaObjectRetrievalFailureException

Question

我遇到一个问题，当我删除 ManyToOne 关系的多方记录时，它可以工作，但在下一个数据库事务中，我收到一个异常，说找不到我刚刚删除的实体(例如，当尝试添加另一个链接说找不到我刚刚删除的链接)。我在数据库中验证了该记录正在被删除。

我正在使用 Spring MVC 和 Spring Data JPA 与 Hibernate。我有一个用户类和一个 NewsLink 类。一个用户可以有许多新闻链接，我想删除其中一个新闻链接。我只是通过构建一个简单的应用程序来学习如何自己使用 Spring 框架。所以这对我来说很新鲜。我感谢任何帮助!

用户实体类

@Entity
@Table(name = "users")
public class User implements Serializable{

@Id 
@Column(name = "idusers")
@GeneratedValue(strategy = GenerationType.AUTO)     
private Long id;

....    

@OneToMany(mappedBy="user", fetch= FetchType.EAGER, cascade=CascadeType.ALL, orphanRemoval= true)
private Set<NewsLink> newsLink;

NewsLink 实体类

@Entity
@Table(name = "news_links")
public class NewsLink implements Serializable{

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

@Column(insertable=false, updatable=false)
private Long idusers;   
....

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

这是服务类中正在执行删除的方法。我认为这是我做得不正确的部分:

@Override
@Transactional
public User deleteNewsLink(int id, User user){

    Iterator<NewsLink> links = user.getNewsLink().iterator();

    while(links.hasNext()){
        NewsLink link = links.next();

        if (link.getId() == id){
            links.remove();
        }

    }

    userRepository.save(user);

    return user;
}

这是我看到的异常:

Request processing failed; nested exception is  org.springframework.orm.jpa.JpaObjectRetrievalFailureException: Unable to find com.test.dailyemail.repository.NewsLink with id 8; nested exception is javax.persistence.EntityNotFoundException: Unable to find com.test.dailyemail.repository.NewsLink with id 8
javax.persistence.EntityNotFoundException: Unable to find com.test.dailyemail.repository.NewsLink with id 8
at org.hibernate.ejb.Ejb3Configuration$Ejb3EntityNotFoundDelegate.handleEntityNotFound(Ejb3Configuration.java:155)
at org.hibernate.event.internal.DefaultLoadEventListener.load(DefaultLoadEventListener.java:210)
at org.hibernate.event.internal.DefaultLoadEventListener.proxyOrLoad(DefaultLoadEventListener.java:260)
at org.hibernate.event.internal.DefaultLoadEventListener.onLoad(DefaultLoadEventListener.java:148)
at org.hibernate.internal.SessionImpl.fireLoad(SessionImpl.java:1078)
at org.hibernate.internal.SessionImpl.internalLoad(SessionImpl.java:1005)
at org.hibernate.type.EntityType.resolveIdentifier(EntityType.java:651)
at org.hibernate.type.EntityType.resolve(EntityType.java:471)
at org.hibernate.type.EntityType.replace(EntityType.java:328)
at org.hibernate.type.CollectionType.preserveSnapshot(CollectionType.java:581)
at org.hibernate.type.CollectionType.replaceElements(CollectionType.java:534)
at org.hibernate.type.CollectionType.replace(CollectionType.java:664)
at org.hibernate.type.TypeHelper.replace(TypeHelper.java:177)
at org.hibernate.event.internal.DefaultMergeEventListener.copyValues(DefaultMergeEventListener.java:372)
at org.hibernate.event.internal.DefaultMergeEventListener.entityIsDetached(DefaultMergeEventListener.java:309)
at org.hibernate.event.internal.DefaultMergeEventListener.onMerge(DefaultMergeEventListener.java:151)
at org.hibernate.event.internal.DefaultMergeEventListener.onMerge(DefaultMergeEventListener.java:76)
at org.hibernate.internal.SessionImpl.fireMerge(SessionImpl.java:903)
at org.hibernate.internal.SessionImpl.merge(SessionImpl.java:887)
at org.hibernate.internal.SessionImpl.merge(SessionImpl.java:891)
at org.hibernate.ejb.AbstractEntityManagerImpl.merge(AbstractEntityManagerImpl.java:879)

Answer 1

我不确定这是否是您的问题，因为我看不到其余的代码，但我认为您应该返回 User 实例 return by userRepository.save( user) 而不是原始的 user 对象，如果您在删除 NewsLink 后仍想使用该对象。

在save方法的javadoc中它说:

Saves a given entity. Use the returned instance for further operations as the save operation might have changed the entity instance completely.

尝试这样的事情:

@Override
@Transactional
public User deleteNewsLink(int id, User user){

    Iterator<NewsLink> links = user.getNewsLink().iterator();

    while(links.hasNext()){
        NewsLink link = links.next();

        if (link.getId() == id){
            links.remove();
            break;
        }

    }

    return userRepository.save(user);
}