Erro ao executar query

public class PedidoDAO {
    
    EntityManagerFactory emf = Persistence.createEntityManagerFactory("ReportPU");
    EntityManager em = emf.createEntityManager();
 
    
    public List<Itensguia> listaritens() {
        List<Itensguia> itensguia = null;
        try {
            Query query = em.createQuery(
                    "Select i from Itensguia i");
            itensguia = query.getResultList();
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            em.close();
        }
        return itensguia;
    }

GRAVE: ‘java.lang.IllegalStateException’ recebido ao invocar escuta de ação ‘#{pedidoControle.gerarRelatorio}’ para o componente 'j_idt8’

GRAVE: java.lang.IllegalStateException: Attempting to execute an operation on a closed EntityManager.

at org.eclipse.persistence.internal.jpa.EntityManagerImpl.verifyOpen(EntityManagerImpl.java:1665)

at org.eclipse.persistence.internal.jpa.EntityManagerImpl.close(EntityManagerImpl.java:1529)

at pedidos.DAO.PedidoDAO.listaritens(PedidoDAO.java:35)

at pedidos.controle.PedidoControle.gerarRelatorio(PedidoControle.java:87)

at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)

at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)

at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)

at java.lang.reflect.Method.invoke(Method.java:597)

at com.sun.el.parser.AstValue.invoke(AstValue.java:254)

at com.sun.el.MethodExpressionImpl.invoke(MethodExpressionImpl.java:302)

at javax.faces.event.MethodExpressionActionListener.processAction(MethodExpressionActionListener.java:153)

at javax.faces.event.ActionEvent.processListener(ActionEvent.java:88)

at javax.faces.component.UIComponentBase.broadcast(UIComponentBase.java:769)

at javax.faces.component.UICommand.broadcast(UICommand.java:300)

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)