Question

我有一些实体：

@Entity
public class Event{

    @Id    
    @GeneratedValue(strategy = GenerationType.IDENTITY)  
    @Column(name = "event_id")
    private long eventId;   

    @ManyToOne(fetch = FetchType.LAZY)
    @JoinColumn(name = "host_id")  
    private Host host;
}

@Entity
public class Host{

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Column(name = "id")   
    private long id;   

    @Column(name = "host_id")
    private long hostId;
}

@Repository
public class EventDao{       

   @PersistenceContext
   private EntityManager em;

   @Transactional
   public List<Event> findEventAfterId(long eventId, long hostId){
      Query q=em.createNativeQuery("SELECT * FROM event WHERE event_id>? AND host_id=?, Event.class);
      q.setParameter(1, eventId);
      q.setParameter(2, hostId);      
      return (List<Event>)q.getResultList();
   }    
}

我正在尝试从此原生查询中获取事件：

SELECT * FROM event WHERE event_id>4442 AND host_id=35;

并获得此异常javax.persistence.EntityNotFoundException: Unable to find entity.Host with id 35但是在我的数据库中我有host_id 35的主机。如何使用host_id列将我的事件实体映射到主机？谢谢。

UPD：

   Query q=em.createNativeQuery("SELECT * FROM event WHERE event_id>? AND host_id=?, Event.class);
    q.setParameter(1, eventId);
    q.setParameter(2, hostId);      
    return (List<Event>)q.getResultList();

以下是完全例外：

    javax.persistence.EntityNotFoundException: Unable to find monitoring.reporter.entity.Host with id 35
 at org.hibernate.jpa.boot.internal.EntityManagerFactoryBuilderImpl$JpaEntityNotFoundDelegate.handleEntityNotFound(EntityManagerFactoryBuilderImpl.java:181)
 at org.hibernate.event.internal.DefaultLoadEventListener.load(DefaultLoadEventListener.java:218)
 at org.hibernate.event.internal.DefaultLoadEventListener.proxyOrLoad(DefaultLoadEventListener.java:274)
 at org.hibernate.event.internal.DefaultLoadEventListener.onLoad(DefaultLoadEventListener.java:150)
 at org.hibernate.internal.SessionImpl.fireLoad(SessionImpl.java:1070)
 at org.hibernate.internal.SessionImpl.internalLoad(SessionImpl.java:989)
 at org.hibernate.type.EntityType.resolveIdentifier(EntityType.java:716)
 at org.hibernate.type.EntityType.resolve(EntityType.java:502)
 at org.hibernate.engine.internal.TwoPhaseLoad.doInitializeEntity(TwoPhaseLoad.java:170)
 at org.hibernate.engine.internal.TwoPhaseLoad.initializeEntity(TwoPhaseLoad.java:144)
 at org.hibernate.loader.Loader.initializeEntitiesAndCollections(Loader.java:1114)
 at org.hibernate.loader.Loader.processResultSet(Loader.java:972)
 at org.hibernate.loader.Loader.doQuery(Loader.java:920)
 at org.hibernate.loader.Loader.doQueryAndInitializeNonLazyCollections(Loader.java:354)
 at org.hibernate.loader.Loader.doList(Loader.java:2553)
 at org.hibernate.loader.Loader.doList(Loader.java:2539)
 at org.hibernate.loader.Loader.listIgnoreQueryCache(Loader.java:2369)
 at org.hibernate.loader.Loader.list(Loader.java:2364)
 at org.hibernate.loader.custom.CustomLoader.list(CustomLoader.java:353)
 at org.hibernate.internal.SessionImpl.listCustomQuery(SessionImpl.java:1873)
 at org.hibernate.internal.AbstractSessionImpl.list(AbstractSessionImpl.java:311)
 at org.hibernate.internal.SQLQueryImpl.list(SQLQueryImpl.java:141)
 at org.hibernate.jpa.internal.QueryImpl.list(QueryImpl.java:573)
 at org.hibernate.jpa.internal.QueryImpl.getResultList(QueryImpl.java:449)

Answer 1

尝试SQL注入的代码

Query q=em.createNativeQuery("SELECT * FROM event WHERE event_id>:event_id AND host_id=:host_id, Event.class);
      q.setParameter("event_id", eventId);
      q.setParameter("host_id", hostId);

Answer 2

你的错误太小了，要清楚地解释清楚我必须在这里写出很多理论，这里的好消息是我有足够的耐心在这里写下所有的理论。

让我从Event类开始，在Event类中，您有Host和Event指向Host的主键。

在Host类中，主键名是＆＃39; id＆＃39;，但在Event类中，对应的列名是host_id。

最后你的表结构如下所示

enter image description here

在Event类中，host_id存在，但它指向Host类的主键，即id

所以Event的host_id指向Host的id列，现在让我们说主机表id列由1组成，因为它是自动递增的，而host_id = 35就是你。

但在事件表中，host_id指向值为1的主机表id。但您的查询是在事件表中搜索host_id = 35。要避免此问题，在Host类中，您必须自动生成host_id主键并且不生成，将手动值分配给host_id。你可以在下面看到相应的类：

@Entity
public class Event{

   @Id    
   @GeneratedValue(strategy = GenerationType.IDENTITY)  
   @Column(name = "event_id")
   private long eventId;   

   @ManyToOne(fetch = FetchType.LAZY)
   @JoinColumn(name = "host_id")  
   private Host host;
}

@Entity
public class Host{

   @Column(name = "id")   
   private long id;   
   @Id
   @Column(name = "host_id")
   private long hostId;
}

@Repository
public class EventDao{       

   @PersistenceContext
   private EntityManager em;

   @Transactional
   public List<Event> findEventAfterId(long eventId, long hostId){
      Query q=em.createNativeQuery("SELECT * FROM event WHERE event_id>? AND host_id=?, Event.class);
      q.setParameter(1, eventId);
      q.setParameter(2, hostId);      
      return (List<Event>)q.getResultList();
   }    
}

Hibernate ManyToOne映射不在PKey上

2 个答案: