spring -> org.hibernate.Hibernate异常：非法尝试将集合与两个打开的会话相关联

Question

在我当前的 spring 项目中，当我的应用程序尝试执行此方法时：

  public void setPedido(Cliente current) {
    Pedido novo = new Pedido();
    novo.setData(new Date());
    novo.setListaDeProdutos(current.getCestaDeCompras());
    pedido.insert(novo);

    if(current.getListaDePedidos() == null)
      current.setListaDePedidos(new ArrayList<Pedido>());

    current.getListaDePedidos().add(novo);
    current.getCestaDeCompras().clear();
    cliente.update(current);
  }

我得到了这个错误:

Caused by: org.hibernate.HibernateException: Illegal attempt to associate a collection with two open sessions
        at org.hibernate.collection.internal.AbstractPersistentCollection.setCurrentSession(AbstractPersistentCollection.java:633)
        at org.hibernate.event.internal.WrapVisitor.processCollection(WrapVisitor.java:66)
        at org.hibernate.event.internal.AbstractVisitor.processValue(AbstractVisitor.java:121)
        at org.hibernate.event.internal.WrapVisitor.processValue(WrapVisitor.java:125)
        at org.hibernate.event.internal.AbstractVisitor.processEntityPropertyValues(AbstractVisitor.java:76)
        at org.hibernate.event.internal.AbstractSaveEventListener.visitCollectionsBeforeSave(AbstractSaveEventListener.java:372)
        at org.hibernate.event.internal.AbstractSaveEventListener.performSaveOrReplicate(AbstractSaveEventListener.java:273)
        at org.hibernate.event.internal.AbstractSaveEventListener.performSave(AbstractSaveEventListener.java:194)
        at org.hibernate.event.internal.AbstractSaveEventListener.saveWithGeneratedId(AbstractSaveEventListener.java:125)
        at org.hibernate.jpa.event.internal.core.JpaPersistEventListener.saveWithGeneratedId(JpaPersistEventListener.java:84)
        at org.hibernate.event.internal.DefaultPersistEventListener.entityIsTransient(DefaultPersistEventListener.java:206)
        at org.hibernate.event.internal.DefaultPersistEventListener.onPersist(DefaultPersistEventListener.java:149)
        at org.hibernate.event.internal.DefaultPersistEventListener.onPersist(DefaultPersistEventListener.java:75)
        at org.hibernate.internal.SessionImpl.firePersist(SessionImpl.java:811)
        at org.hibernate.internal.SessionImpl.persist(SessionImpl.java:784)
        at org.hibernate.internal.SessionImpl.persist(SessionImpl.java:789)
        at org.hibernate.jpa.spi.AbstractEntityManagerImpl.persist(AbstractEntityManagerImpl.java:1181)
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
        at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
        at java.lang.reflect.Method.invoke(Method.java:606)
        at org.springframework.orm.jpa.ExtendedEntityManagerCreator$ExtendedEntityManagerInvocationHandler.invoke(ExtendedEntityManagerCreator.java:344)
        at com.sun.proxy.$Proxy79.persist(Unknown Source)
        at org.store.generic.persistence.Dao.insert(Dao.java:29)
        at org.store.generic.persistence.Dao$$FastClassBySpringCGLIB$$ac46d9f5.invoke(<generated>)
        at org.springframework.cglib.proxy.MethodProxy.invoke(MethodProxy.java:204)
        at org.springframework.aop.framework.CglibAopProxy$CglibMethodInvocation.invokeJoinpoint(CglibAopProxy.java:717)
        at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:157)
        at org.springframework.dao.support.PersistenceExceptionTranslationInterceptor.invoke(PersistenceExceptionTranslationInterceptor.java:136)

我的Dao类（插入方法的位置）是这样的：

public class Dao<E> {

    @Autowired
    private EntityManagerFactory factory;

    protected Class<? extends Model> clazz;

    public Dao(Class<? extends Model> clazz) {
        this.clazz = clazz;
    }

    public EntityManager getEntityManager() {
        return factory.createEntityManager();
    }

    public void insert(E object) {
        EntityManager entityManager = getEntityManager();
        entityManager.getTransaction().begin();
        entityManager.persist(object);
        entityManager.getTransaction().commit();
    }

    ...
}

我还尝试在Dao类中的insert、update和delete方法以及在服务类中使用它们的方法中添加注释@Transaction，但同样的问题也会发生。

有人能看出我做错了什么吗？

ps.：我试图保存的实体类是：

@Entity
public class Pedido extends Model {
  @Id
  @GeneratedValue(strategy=GenerationType.IDENTITY)
  @Order(value = 1)
  private Integer id;

  @Order(value = 2)
  private Date data;

  @ManyToMany
  @JoinTable(name="listaDeProdutos", joinColumns={@JoinColumn(name="fk_pedido")}, inverseJoinColumns={@JoinColumn(name="fk_produto")})
  @LazyCollection(LazyCollectionOption.FALSE)
  @Order(value = 3)
  private List<Produto> listaDeProdutos;
}

Answer 1

好的，实际上生成此错误的问题是由于 Dao 类的方法中缺少 close（） 指令。我将代码修改为：

public void insert(E object) {
    EntityManager entityManager = getEntityManager();
    entityManager.getTransaction().begin();
    entityManager.persist(object);
    entityManager.getTransaction().commit();
    entityManager.close();
}

现在一切正常。