java - 延迟初始化集合失败，从 org.hibernate.classic.Lifecycle 的 onload 方法访问时没有 session 或 session 被关闭

Question

这个问题已经有答案了:

Failed to lazily initialize a collection, no session or session was closed (despite eagerly fetching) (1 个回答)

已关闭 9 年前。

代码

l_details 的

pin 具有引用 x_details 主键 的外部约束，这里我使用 XDetails 类中的单向关系。

实体:

    @Entity
    @Table(name = "x_details")
    public class XDetails implements Lifecycle {
    private int y;
    ....
    .....
    private Set<LDetails> lDetails = new HashSet<LDetails>(0);
    .........
    ..........
        @OneToMany(fetch = FetchType.LAZY)
    @JoinColumn(name="pin")
    public Set<LDetails> getLDetails() {
        return this.lDetails;
    }

    @Override
    public void onLoad(Session s, Serializable id) {
        System.out.println("inside  load");
        try{
            if((lDetails!=null)){
                System.out.println("size of lDetails"+lDetails.size());
            }   
        }
        catch(Exception exception){
            exception.printStackTrace();
        }
    }
    }

    @Entity
    @Table(name = "l_details")
    public class LDetails {

    private Integer id1;
    private Integer pin;
    ....
    @Id
    @GeneratedValue(strategy = IDENTITY)
    @Column(name = "id1", unique = true, nullable = false)
    public Integer getId1() {
        return this.id1;
    }

    public void setId1(Integer id1) {
        this.id1 = id1;
    }
    @Column(name="pin")
    public Integer getPin() {
        return this.pin;
    }

    public void setPin(Integer pin) {
        this.pin = pin;
    }

    }

主线程:

    Session session=HibernateUtil.getSessionFactory().getCurrentSession();
    session.beginTransaction();
    Criteria criteria=session.createCriteria(XDetails.class);
    criteria.createAlias("lDetails", "status",CriteriaSpecification.INNER_JOIN);
    criteria.setFetchMode("status", FetchMode.JOIN); 
    List<XDetails> details=criteria.list();
    session.getTransaction().commit();

异常(在 onload 内):

    org.hibernate.LazyInitializationException: failed to lazily initialize a collection, no session or session was closed
    at rg.hibernate.collection.AbstractPersistentCollection.throwLazyInitializationException(AbstractPersistentCollection.java:383)
    at org.hibernate.collection.AbstractPersistentCollection.throwLazyInitializationExceptionIfNotConnected(AbstractPersistentCollection.java:375)
    at org.hibernate.collection.AbstractPersistentCollection.readSize(AbstractPersistentCollection.java:122)
    at org.hibernate.collection.PersistentSet.size(PersistentSet.java:162)
    at com.hibernate.test.pendingdict3.XDetails.onLoad(XDetails.java:588)
    at org.hibernate.event.def.DefaultPostLoadEventListener.onPostLoad(DefaultPostLoadEventListener.java:73)
    at org.hibernate.engine.TwoPhaseLoad.initializeEntity(TwoPhaseLoad.java:234)
    at org.hibernate.loader.Loader.initializeEntitiesAndCollections(Loader.java:898)
    at org.hibernate.loader.Loader.doQuery(Loader.java:773)
    at org.hibernate.loader.Loader.doQueryAndInitializeNonLazyCollections(Loader.java:270)
    at org.hibernate.loader.Loader.doList(Loader.java:2449)
    at org.hibernate.loader.Loader.listIgnoreQueryCache(Loader.java:2192)
    at org.hibernate.loader.Loader.list(Loader.java:2187)
    at org.hibernate.loader.criteria.CriteriaLoader.list(CriteriaLoader.java:119)
    at org.hibernate.impl.SessionImpl.list(SessionImpl.java:1706)
    at org.hibernate.impl.CriteriaImpl.list(CriteriaImpl.java:347)
    at com.hibernate.test.main4.HibernateStandaloneMain.main(HibernateStandaloneMain.java:24)

我正在使用 Hibernate 3.5.6 Final 依赖项、mysql 数据库，并且正在运行 hibernatestandalone 应用程序。

# onload method
       @Override
    public void onLoad(Session s, Serializable id) {
        System.out.println("inside  load");
        try{
            if((lDetails!=null)){
                System.out.println("size of lDetails"+lDetails.size());
            }   
        }
        catch(Exception exception){
            exception.printStackTrace();
        }
    }

Answer 1

问题是你选择了LAZY正在加载，但当您第一次访问集合的元素时，您的 session 已经关闭。您需要EAGER获取您的Set<LDetails>或保持 session 打开，直到所有操作完成。