Solution to "Illegal attempt to associate a collection with two open sessions"

[Rafael Gabriel]

Hello everybody!
I need a solution to my problem without affecting my whole application.

I'm getting the error "Illegal attempt to associate a collection with two open sessions" and I can not solve.

My DAO:

    public void deleteC(Cliente e) {
        Session session = HibernateUtil.getSession();
        Transaction tx = session.beginTransaction();
        session.delete(e);
        tx.commit();
    }
    public Cliente getClienteById(long pes_id) {
        Session session = HibernateUtil.openSession();
        return (Cliente) session.get(Cliente.class, pes_id);
    }

My HibernateUtil:

public class HibernateUtil {
    private static SessionFactory sessionFactory;
    static {
        try {
            sessionFactory = new AnnotationConfiguration().configure().buildSessionFactory();
        } catch (Throwable ex) {
            System.err.println("Initial SessionFactory creation failed." + ex);
            throw new ExceptionInInitializerError(ex);
        }
    }
    public static SessionFactory getSessionFactory() {
        if (sessionFactory == null) {
            try {
                sessionFactory = new AnnotationConfiguration().configure().buildSessionFactory();
            } catch (Throwable ex) {
                System.err.println("Initial SessionFactory creation failed." + ex);
                throw new ExceptionInInitializerError(ex);
            }

        }
        return sessionFactory;
    }
    public static Session getSession() {
        return sessionFactory
                .getCurrentSession();
    }
    public static Session openSession() {
        return sessionFactory
                .openSession();
    }
}

My code getting error:

ClienteDao clienteDao = new ClienteDao();
cliente = clienteDao.getClienteById(1);
clienteDao.deleteC(cliente);

Error is in "clienteDao.deleteC(cliente)...

I can not close the session "getClienteById" because my fields LAZY not work.
What can I do?

Thanks!

My entity:

@Entity
@Table(name = "Cliente")
@PrimaryKeyJoinColumn(name="pes_id")  
public class Cliente extends Pessoa implements Serializable {
    @Column(name = "cli_codigo", nullable=false)
    private long cli_codigo;
    @Column(name = "cli_razao", nullable=false)
    private String cli_razao;
    @Column(name = "cli_cnpj", nullable=false)
    private String cli_cnpj;
    @Column(name = "cli_ie", nullable=false)
    private String cli_ie;
    @Column(name = "cli_loja", nullable=false)
    private int cli_loja;
    @JoinColumn(name="ven_id", nullable = false) 
    @OneToMany
    private Vendedor ven_id;

Full error:

WARNING: #{deletarClienteBean.deletarCliente}: org.hibernate.HibernateException: Illegal attempt to associate a collection with two open sessions
javax.faces.FacesException: #{deletarClienteBean.deletarCliente}: org.hibernate.HibernateException: Illegal attempt to associate a collection with two open sessions
	at com.sun.faces.application.ActionListenerImpl.processAction(ActionListenerImpl.java:118)
	at javax.faces.component.UICommand.broadcast(UICommand.java:315)
	at javax.faces.component.UIViewRoot.broadcastEvents(UIViewRoot.java:794)
	at javax.faces.component.UIViewRoot.processApplication(UIViewRoot.java:1259)
	at com.sun.faces.lifecycle.InvokeApplicationPhase.execute(InvokeApplicationPhase.java:81)
	at com.sun.faces.lifecycle.Phase.doPhase(Phase.java:101)
	at com.sun.faces.lifecycle.LifecycleImpl.execute(LifecycleImpl.java:118)
	at javax.faces.webapp.FacesServlet.service(FacesServlet.java:593)
	at org.apache.catalina.core.StandardWrapper.service(StandardWrapper.java:1550)
	at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:281)
	at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:175)
	at org.apache.catalina.core.StandardPipeline.doInvoke(StandardPipeline.java:655)
	at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:595)
	at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:161)
	at org.apache.catalina.connector.CoyoteAdapter.doService(CoyoteAdapter.java:331)
	at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:231)
	at com.sun.enterprise.v3.services.impl.ContainerMapper$AdapterCallable.call(ContainerMapper.java:317)
	at com.sun.enterprise.v3.services.impl.ContainerMapper.service(ContainerMapper.java:195)
	at com.sun.grizzly.http.ProcessorTask.invokeAdapter(ProcessorTask.java:860)
	at com.sun.grizzly.http.ProcessorTask.doProcess(ProcessorTask.java:757)
	at com.sun.grizzly.http.ProcessorTask.process(ProcessorTask.java:1056)
	at com.sun.grizzly.http.DefaultProtocolFilter.execute(DefaultProtocolFilter.java:229)
	at com.sun.grizzly.DefaultProtocolChain.executeProtocolFilter(DefaultProtocolChain.java:137)
	at com.sun.grizzly.DefaultProtocolChain.execute(DefaultProtocolChain.java:104)
	at com.sun.grizzly.DefaultProtocolChain.execute(DefaultProtocolChain.java:90)
	at com.sun.grizzly.http.HttpProtocolChain.execute(HttpProtocolChain.java:79)
	at com.sun.grizzly.ProtocolChainContextTask.doCall(ProtocolChainContextTask.java:54)
	at com.sun.grizzly.SelectionKeyContextTask.call(SelectionKeyContextTask.java:59)
	at com.sun.grizzly.ContextTask.run(ContextTask.java:71)
	at com.sun.grizzly.util.AbstractThreadPool$Worker.doWork(AbstractThreadPool.java:532)
	at com.sun.grizzly.util.AbstractThreadPool$Worker.run(AbstractThreadPool.java:513)
	at java.lang.Thread.run(Thread.java:722)
Caused by: javax.faces.el.EvaluationException: org.hibernate.HibernateException: Illegal attempt to associate a collection with two open sessions
	at javax.faces.component.MethodBindingMethodExpressionAdapter.invoke(MethodBindingMethodExpressionAdapter.java:102)
	at com.sun.faces.application.ActionListenerImpl.processAction(ActionListenerImpl.java:102)
	... 31 more
Caused by: org.hibernate.HibernateException: Illegal attempt to associate a collection with two open sessions
	at org.hibernate.collection.AbstractPersistentCollection.setCurrentSession(AbstractPersistentCollection.java:410)
	at org.hibernate.event.def.OnUpdateVisitor.processCollection(OnUpdateVisitor.java:43)
	at org.hibernate.event.def.AbstractVisitor.processValue(AbstractVisitor.java:101)
	at org.hibernate.event.def.AbstractVisitor.processValue(AbstractVisitor.java:61)
	at org.hibernate.event.def.AbstractVisitor.processEntityPropertyValues(AbstractVisitor.java:55)
	at org.hibernate.event.def.AbstractVisitor.process(AbstractVisitor.java:123)
	at org.hibernate.event.def.DefaultDeleteEventListener.onDelete(DefaultDeleteEventListener.java:101)
	at org.hibernate.event.def.DefaultDeleteEventListener.onDelete(DefaultDeleteEventListener.java:52)
	at org.hibernate.impl.SessionImpl.fireDelete(SessionImpl.java:766)
	at org.hibernate.impl.SessionImpl.delete(SessionImpl.java:744)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:601)
	at org.hibernate.context.ThreadLocalSessionContext$TransactionProtectionWrapper.invoke(ThreadLocalSessionContext.java:301)
	at $Proxy145.delete(Unknown Source)
	at br.com.zanzini.dao.ClienteDao.excluir(ClienteDao.java:31)
	at br.com.zanzini.bean.DeletarClienteBean.deletarCliente(DeletarClienteBean.java:41)
	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:601)
	at com.sun.el.parser.AstValue.invoke(AstValue.java:254)
	at com.sun.el.MethodExpressionImpl.invoke(MethodExpressionImpl.java:302)
	at com.sun.faces.facelets.el.TagMethodExpression.invoke(TagMethodExpression.java:105)
	at javax.faces.component.MethodBindingMethodExpressionAdapter.invoke(MethodBindingMethodExpressionAdapter.java:88)
	... 32 more