Ajuda Inserir registro Primefaces

Pessoal estou tentando inserir um registro no datatable utilizando o primefaces,porém ele nem apresenta erro

Informações:   Hibernate: select usuario0_.codigo as codigo1_1_, usuario0_.usuario as usuario2_1_, usuario0_.senha as senha3_1_ from public.usuario usuario0_
Advertência:   /views/usuario/index.xhtml @66,118 value="#{usuarioBean.selectedUsuario.usuario}": Target Unreachable, 'null' returned null
javax.el.PropertyNotFoundException: /views/usuario/index.xhtml @66,118 value="#{usuarioBean.selectedUsuario.usuario}": Target Unreachable, 'null' returned null
	at com.sun.faces.facelets.el.TagValueExpression.getType(TagValueExpression.java:100)
	at org.primefaces.util.ComponentUtils.getConverter(ComponentUtils.java:128)
	at org.primefaces.renderkit.InputRenderer.getConvertedValue(InputRenderer.java:171)
	at javax.faces.component.UIInput.getConvertedValue(UIInput.java:1045)
	at javax.faces.component.UIInput.validate(UIInput.java:975)
	at javax.faces.component.UIInput.executeValidate(UIInput.java:1248)
	at javax.faces.component.UIInput.processValidators(UIInput.java:712)
	at javax.faces.component.UIComponentBase.processValidators(UIComponentBase.java:1258)
	at javax.faces.component.UIForm.processValidators(UIForm.java:253)
	at javax.faces.component.UIComponentBase.processValidators(UIComponentBase.java:1258)
	at org.primefaces.component.dialog.Dialog.processValidators(Dialog.java:385)
	at javax.faces.component.UIComponentBase.processValidators(UIComponentBase.java:1258)
	at javax.faces.component.UIComponentBase.processValidators(UIComponentBase.java:1258)
	at javax.faces.component.UIViewRoot.processValidators(UIViewRoot.java:1195)
	at com.sun.faces.lifecycle.ProcessValidationsPhase.execute(ProcessValidationsPhase.java:76)
	at com.sun.faces.lifecycle.Phase.doPhase(Phase.java:101)
	at com.sun.faces.lifecycle.LifecycleImpl.execute(LifecycleImpl.java:198)
	at javax.faces.webapp.FacesServlet.service(FacesServlet.java:646)
	at org.apache.catalina.core.StandardWrapper.service(StandardWrapper.java:1682)
	at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:318)
	at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:160)
	at org.apache.catalina.core.StandardPipeline.doInvoke(StandardPipeline.java:734)
	at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:673)
	at com.sun.enterprise.web.WebPipeline.invoke(WebPipeline.java:99)
	at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:174)
	at org.apache.catalina.connector.CoyoteAdapter.doService(CoyoteAdapter.java:415)
	at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:282)
	at com.sun.enterprise.v3.services.impl.ContainerMapper$HttpHandlerCallable.call(ContainerMapper.java:459)
	at com.sun.enterprise.v3.services.impl.ContainerMapper.service(ContainerMapper.java:167)
	at org.glassfish.grizzly.http.server.HttpHandler.runService(HttpHandler.java:201)
	at org.glassfish.grizzly.http.server.HttpHandler.doHandle(HttpHandler.java:175)
	at org.glassfish.grizzly.http.server.HttpServerFilter.handleRead(HttpServerFilter.java:235)
	at org.glassfish.grizzly.filterchain.ExecutorResolver$9.execute(ExecutorResolver.java:119)
	at org.glassfish.grizzly.filterchain.DefaultFilterChain.executeFilter(DefaultFilterChain.java:284)
	at org.glassfish.grizzly.filterchain.DefaultFilterChain.executeChainPart(DefaultFilterChain.java:201)
	at org.glassfish.grizzly.filterchain.DefaultFilterChain.execute(DefaultFilterChain.java:133)
	at org.glassfish.grizzly.filterchain.DefaultFilterChain.process(DefaultFilterChain.java:112)
	at org.glassfish.grizzly.ProcessorExecutor.execute(ProcessorExecutor.java:77)
	at org.glassfish.grizzly.nio.transport.TCPNIOTransport.fireIOEvent(TCPNIOTransport.java:561)
	at org.glassfish.grizzly.strategies.AbstractIOStrategy.fireIOEvent(AbstractIOStrategy.java:112)
	at org.glassfish.grizzly.strategies.WorkerThreadIOStrategy.run0(WorkerThreadIOStrategy.java:117)
	at org.glassfish.grizzly.strategies.WorkerThreadIOStrategy.access$100(WorkerThreadIOStrategy.java:56)
	at org.glassfish.grizzly.strategies.WorkerThreadIOStrategy$WorkerThreadRunnable.run(WorkerThreadIOStrategy.java:137)
	at org.glassfish.grizzly.threadpool.AbstractThreadPool$Worker.doWork(AbstractThreadPool.java:565)
	at org.glassfish.grizzly.threadpool.AbstractThreadPool$Worker.run(AbstractThreadPool.java:545)
	at java.lang.Thread.run(Thread.java:745)
Caused by: javax.el.PropertyNotFoundException: Target Unreachable, 'null' returned null
	at com.sun.el.parser.AstValue.getTarget(AstValue.java:192)
	at com.sun.el.parser.AstValue.getType(AstValue.java:86)
	at com.sun.el.ValueExpressionImpl.getType(ValueExpressionImpl.java:201)
	at org.jboss.weld.el.WeldValueExpression.getType(WeldValueExpression.java:93)
	at com.sun.faces.facelets.el.TagValueExpression.getType(TagValueExpression.java:98)
	... 45 more

Grave:   javax.el.PropertyNotFoundException: /views/usuario/index.xhtml @66,118 value="#{usuarioBean.selectedUsuario.usuario}": Target Unreachable, 'null' returned null
	at com.sun.faces.facelets.el.TagValueExpression.getType(TagValueExpression.java:100)
	at org.primefaces.util.ComponentUtils.getConverter(ComponentUtils.java:128)
	at org.primefaces.renderkit.InputRenderer.getConvertedValue(InputRenderer.java:171)
	at javax.faces.component.UIInput.getConvertedValue(UIInput.java:1045)
	at javax.faces.component.UIInput.validate(UIInput.java:975)
	at javax.faces.component.UIInput.executeValidate(UIInput.java:1248)
	at javax.faces.component.UIInput.processValidators(UIInput.java:712)
	at javax.faces.component.UIComponentBase.processValidators(UIComponentBase.java:1258)
	at javax.faces.component.UIForm.processValidators(UIForm.java:253)
	at javax.faces.component.UIComponentBase.processValidators(UIComponentBase.java:1258)
	at org.primefaces.component.dialog.Dialog.processValidators(Dialog.java:385)
	at javax.faces.component.UIComponentBase.processValidators(UIComponentBase.java:1258)
	at javax.faces.component.UIComponentBase.processValidators(UIComponentBase.java:1258)
	at javax.faces.component.UIViewRoot.processValidators(UIViewRoot.java:1195)
	at com.sun.faces.lifecycle.ProcessValidationsPhase.execute(ProcessValidationsPhase.java:76)
	at com.sun.faces.lifecycle.Phase.doPhase(Phase.java:101)
	at com.sun.faces.lifecycle.LifecycleImpl.execute(LifecycleImpl.java:198)
	at javax.faces.webapp.FacesServlet.service(FacesServlet.java:646)
	at org.apache.catalina.core.StandardWrapper.service(StandardWrapper.java:1682)
	at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:318)
	at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:160)
	at org.apache.catalina.core.StandardPipeline.doInvoke(StandardPipeline.java:734)
	at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:673)
	at com.sun.enterprise.web.WebPipeline.invoke(WebPipeline.java:99)
	at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:174)
	at org.apache.catalina.connector.CoyoteAdapter.doService(CoyoteAdapter.java:415)
	at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:282)
	at com.sun.enterprise.v3.services.impl.ContainerMapper$HttpHandlerCallable.call(ContainerMapper.java:459)
	at com.sun.enterprise.v3.services.impl.ContainerMapper.service(ContainerMapper.java:167)
	at org.glassfish.grizzly.http.server.HttpHandler.runService(HttpHandler.java:201)
	at org.glassfish.grizzly.http.server.HttpHandler.doHandle(HttpHandler.java:175)
	at org.glassfish.grizzly.http.server.HttpServerFilter.handleRead(HttpServerFilter.java:235)
	at org.glassfish.grizzly.filterchain.ExecutorResolver$9.execute(ExecutorResolver.java:119)
	at org.glassfish.grizzly.filterchain.DefaultFilterChain.executeFilter(DefaultFilterChain.java:284)
	at org.glassfish.grizzly.filterchain.DefaultFilterChain.executeChainPart(DefaultFilterChain.java:201)
	at org.glassfish.grizzly.filterchain.DefaultFilterChain.execute(DefaultFilterChain.java:133)
	at org.glassfish.grizzly.filterchain.DefaultFilterChain.process(DefaultFilterChain.java:112)
	at org.glassfish.grizzly.ProcessorExecutor.execute(ProcessorExecutor.java:77)
	at org.glassfish.grizzly.nio.transport.TCPNIOTransport.fireIOEvent(TCPNIOTransport.java:561)
	at org.glassfish.grizzly.strategies.AbstractIOStrategy.fireIOEvent(AbstractIOStrategy.java:112)
	at org.glassfish.grizzly.strategies.WorkerThreadIOStrategy.run0(WorkerThreadIOStrategy.java:117)
	at org.glassfish.grizzly.strategies.WorkerThreadIOStrategy.access$100(WorkerThreadIOStrategy.java:56)
	at org.glassfish.grizzly.strategies.WorkerThreadIOStrategy$WorkerThreadRunnable.run(WorkerThreadIOStrategy.java:137)
	at org.glassfish.grizzly.threadpool.AbstractThreadPool$Worker.doWork(AbstractThreadPool.java:565)
	at org.glassfish.grizzly.threadpool.AbstractThreadPool$Worker.run(AbstractThreadPool.java:545)
	at java.lang.Thread.run(Thread.java:745)
Caused by: javax.el.PropertyNotFoundException: Target Unreachable, 'null' returned null
	at com.sun.el.parser.AstValue.getTarget(AstValue.java:192)
	at com.sun.el.parser.AstValue.getType(AstValue.java:86)
	at com.sun.el.ValueExpressionImpl.getType(ValueExpressionImpl.java:201)
	at org.jboss.weld.el.WeldValueExpression.getType(WeldValueExpression.java:93)
	at com.sun.faces.facelets.el.TagValueExpression.getType(TagValueExpression.java:98)
	... 45 more



public void btnCriarUsuario(ActionEvent actionEvent) {
    UsuarioDao usuarioDao = new UsuarioDaoImpl();
    String msg;
    if(usuarioDao.criar(this.selectedUsuario)) {
        
     msg= "Usuário foi gravado com Sucesso" ;
     
      
    FacesMessage message  = new  FacesMessage(FacesMessage.SEVERITY_INFO, msg ,null);
    FacesContext.getCurrentInstance().addMessage(null, message);
    }else {
        
        msg= "Erro,Usuario não foi cadastrado" ;
        
    FacesMessage messagem  = new  FacesMessage(FacesMessage.SEVERITY_ERROR,msg,null);
    FacesContext.getCurrentInstance().addMessage(null, messagem);
    }



.O meu banco de dados é postgres e o atributo código é bigserial o código é gerado automaticamente . Segue minhas classes para que vocês analisem.


package model;
// Generated 15/11/2014 23:21:06 by Hibernate Tools 4.3.1


import java.io.Serializable;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.Id;
import javax.persistence.Table;

/**
 * Usuario generated by hbm2java
 */
@Entity
@Table(name="usuario"
    ,schema="public"
)
public class Usuario  implements Serializable {


     private Integer codigo;
     private String usuario;
     private String senha;

    public Usuario() {
   this.codigo = 0;
    
    }

	
    public Usuario(Integer codigo) {
        this.codigo = codigo;
    }
    public Usuario(Integer codigo, String usuario, String senha) {
       this.codigo = codigo;
       this.usuario = usuario;
       this.senha = senha;
    }
   
     
    
    
    @Id 
    @Column(name="codigo", unique=true, nullable=false)
    public Integer getCodigo() {
        return this.codigo;
    }
    
    public void setCodigo(Integer codigo) {
        this.codigo = codigo;
    }

    
    @Column(name="usuario", length=40)
    public String getUsuario() {
        return this.usuario;
    }
    
    public void setUsuario(String usuario) {
        this.usuario = usuario;
    }

    
    @Column(name="senha", length=8)
    public String getSenha() {
        return this.senha;
    }
    
    public void setSenha(String senha) {
        this.senha = senha;
    }




}







package dao;

import java.util.List;
import model.Usuario;

/**
 *
 * @author Administrador
 */
public interface UsuarioDao {

    public Usuario findByUsuario(Usuario usuario);

    public Usuario login(Usuario usuario);
    public List<Usuario> findAll();
   public  boolean  criar (Usuario usuario);
   public boolean update(Usuario usuario);
   public boolean delete (Integer codigo);
}




/*

* To change this license header, choose License Headers in Project Properties.
 * To change this template file, choose Tools | Templates
 * and open the template in the editor.
 */
package dao;

import java.util.List;
import model.Usuario;
import org.hibernate.Session;
import util.HibernateUtil;


/**
 *
 * @author Administrador
 */
public class UsuarioDaoImpl implements UsuarioDao {

    @Override
    public Usuario findByUsuario(Usuario usuario) {

           Usuario model = null;
      Session session = HibernateUtil.getSessionFactory().getCurrentSession();
      String sql="FROM Usuario  WHERE usuario = '"+usuario.getUsuario()+"'";
      try {
          
          session.beginTransaction();
          model = (Usuario) session.createQuery(sql).uniqueResult();
          session.beginTransaction().commit();
          
      }catch (Exception e )  {
          
           session.beginTransaction().rollback();
          
      }

        return model;
    }

     
 

    @Override
    public Usuario login(Usuario usuario) {
     Usuario model = this.findByUsuario(usuario);
     if(model != null) {
         
        if(!usuario.getSenha().equals(model.getSenha())) {
            
            model = null;
        } 
     }
    
    return model;
    }

    @Override
    public List<Usuario> findAll() {
     List <Usuario> listado = null;
    Session session = HibernateUtil.getSessionFactory().getCurrentSession();
      String sql="FROM Usuario";
      try {
           
          session.beginTransaction();
          listado = session.createQuery(sql).list();
          session.beginTransaction().commit();
          
         
          
      }catch (Exception e )  {
        session.close();  
       //  session.beginTransaction().rollback();
     
      }

        return listado;
    }

    @Override
    public boolean criar(Usuario usuario) {
       
      boolean flag;
      Session session = HibernateUtil.getSessionFactory().getCurrentSession();
      try {
          session.beginTransaction();
          session.save(usuario);
          session.beginTransaction().commit();
          flag = true;
      }catch (Exception e )  {
        flag = false;
     
        session.beginTransaction().rollback();
      } 
      
      return flag;
             
    }

    

    @Override
    public boolean update(Usuario usuario) {
     
     boolean flag;
      Session session = HibernateUtil.getSessionFactory().getCurrentSession();
      try {
          session.beginTransaction();
          session.update(usuario);
          session.beginTransaction().commit();
          flag = true;
      }catch (Exception e )  {
        flag = false;
        session.beginTransaction().rollback();
      } 
      
      return flag;
             



    }

    @Override
    public boolean delete(Integer codigo) {
   
        boolean flag;
      Session session = HibernateUtil.getSessionFactory().getCurrentSession();
      try {
          session.beginTransaction();
          Usuario usuario = (Usuario) session.load(Usuario.class,codigo);
          session.delete(usuario);
          session.beginTransaction().commit();
          flag = true;
      }catch (Exception e )  {
        flag = false;
        session.beginTransaction().rollback();
      } 
      
      return flag;
             
        
        
    }
   
}

/*
 * To change this license header, choose License Headers in Project Properties.
 * To change this template file, choose Tools | Templates
 * and open the template in the editor.
 */
package bean;

import dao.UsuarioDao;
import dao.UsuarioDaoImpl;
import java.awt.event.ActionEvent;
import java.util.ArrayList;
import java.util.List;
import javax.inject.Named;
import javax.enterprise.context.RequestScoped;
import javax.faces.application.FacesMessage;
import javax.faces.context.FacesContext;
import model.Usuario;

/**
 *
 * @author Administrador
 */
@Named(value = "usuarioBean")
@RequestScoped
public class usuarioBean {

    
     private List<Usuario> usuarios;
     private Usuario selectedUsuario;

    public usuarioBean() {
        
        this.usuarios = new ArrayList<Usuario>();
    }
    
    
    public List<Usuario> getUsuarios() {
        
        UsuarioDao usuarioDao = new UsuarioDaoImpl();
        this.usuarios = usuarioDao.findAll();
        
        return usuarios;
    }

    /**
     * @return the selectedUsuario
     */
    public Usuario getSelectedUsuario() {
        return selectedUsuario;
    }

    public void setSelectedUsuario(Usuario selectedUsuario) {
        this.selectedUsuario = selectedUsuario;
    }
     
    
    
    
public void btnCriarUsuario(ActionEvent actionEvent) {
    UsuarioDao usuarioDao = new UsuarioDaoImpl();
    String msg;
    if(usuarioDao.criar(this.selectedUsuario)) {
        
     msg= "Usuário foi gravado com Sucesso" ;
     
      
    FacesMessage message  = new  FacesMessage(FacesMessage.SEVERITY_INFO, msg ,null);
    FacesContext.getCurrentInstance().addMessage(null, message);
    }else {
        
        msg= "Erro,Usuario não foi cadastrado" ;
        
    FacesMessage messagem  = new  FacesMessage(FacesMessage.SEVERITY_ERROR,msg,null);
    FacesContext.getCurrentInstance().addMessage(null, messagem);
    }
     
        
}

public void btnUpdateUsuario(ActionEvent actionEvent) {
    
    UsuarioDao usuarioDao = new UsuarioDaoImpl();
    String msg;
    if(usuarioDao.update(this.selectedUsuario)) {
        
     msg="Usuário foi atualizado  com Sucesso!";
    }else {
        
        msg="Erro,Usuario não foi Atualizado!";
    }
     
    FacesMessage messagem  = new  FacesMessage(FacesMessage.SEVERITY_INFO,msg,null);
    FacesContext.getCurrentInstance().addMessage(null, messagem);
    
    
}

public void btnDeleteUsuario(ActionEvent actionEvent) {
    
     UsuarioDao usuarioDao = new UsuarioDaoImpl();
    String msg;
    if(usuarioDao.delete(this.selectedUsuario.getCodigo())) {
        
     msg="Usuário foi excluido   com Sucesso!";
    }else {
        
        msg="Erro,Usuario não foi Excluido!";
    }
     
    FacesMessage messagem  = new  FacesMessage(FacesMessage.SEVERITY_INFO,msg,null);
    FacesContext.getCurrentInstance().addMessage(null, messagem);
    
    
}
    
}
  
    

Pagina Web Primefaces


<?xml version='1.0' encoding='UTF-8' ?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml"
      xmlns:ui="http://xmlns.jcp.org/jsf/facelets"
      xmlns:p="http://primefaces.org/ui"
      xmlns:h="http://xmlns.jcp.org/jsf/html"
      xmlns:f="http://xmlns.jcp.org/jsf/core">

    <body>

        <ui:composition template="./../template.xhtml">

            <ui:define name="content">



                <p:growl id="msgs" showDetail="true" />

                <h:form>

                    <p:commandButton id="btnUsuarioCriar"  update=":formCriar" oncomplete=" PF('dialogUsuarioCriar').show()" icon="icon-criar" title="Criar" value="Criar"/>

                </h:form>


                <h:form id="formDataTable">
                    <p:dataTable  var="usuario" value="#{usuarioBean.usuarios}">
                        <f:facet name="header">
                            Basic
                        </f:facet>
                        <p:column headerText="Codigo"  >
                            <h:outputText value="#{usuario.codigo}"  />
                        </p:column>
                        <p:column headerText="Usuario"   >
                            <h:outputText value="#{usuario.usuario}"  />
                        </p:column>
                        <p:column headerText="Senha">
                            <h:outputText value="#{usuario.senha}"  />
                        </p:column>
                        <p:column style="width:80px;text-align: center">

                            <p:commandButton id="btnUptade" update=":formUpdate" oncomplete=" PF('dialogUsuarioUpdate').show()" icon="atualizar"    title="Atualizar">
                                <f:setPropertyActionListener value="#{usuario}" target="#{usuarioBean.selectedUsuario}" />
                            </p:commandButton>

                            <p:commandButton id="btnDelete" update=":formDelete" oncomplete=" PF('dialogUsuarioDelete').show()" icon="deletar" title="Deletar">
                                <f:setPropertyActionListener value="#{usuario}" target="#{usuarioBean.selectedUsuario}" />
                            </p:commandButton>

                        </p:column>
                    </p:dataTable>


                </h:form>



                <h:form id="formCriar">

                    <p:dialog header="Incluir  Usuario" widgetVar="dialogUsuarioCriar"  resizable="false" id="dlgUsuarioCriar" 
                              showEffect="fade"    hideEffect="explode"  modal="true" >

                        <h:panelGrid  id="display" columns="2"  cellpadding="4" style="margin:0 auto;" >

                            <h:outputText value="Codigo" />
                            <p:inputText value="#{usuarioBean.selectedUsuario.codigo}" style="font-weight: bold" />

                            <h:outputText value="Usuario" />
                            <p:inputText  value="#{usuarioBean.selectedUsuario.usuario}" style="font-weight: bold" />

                            <h:outputText value="Senha" />
                            <p:inputText  value="#{usuarioBean.selectedUsuario.senha}" style="font-weight: bold" />
                             
                            <f:facet name="footer">
                          
                                <p:commandButton id="btnUsuarioSalvar"  update=":formDataTable, :msgs" oncomplete="dialogUsuarioCriar.hide()" actionListener="#{usuarioBean.btnCriarUsuario(actionEvent)}" icon="icon-salvar" title="Salvar" value="Salvar"/>
                            <p:commandButton id="btnUsuarioCancelar"   oncomplete=" PF('dialogUsuarioCriar').hide()" icon="icon-cancelar" title="Cancelar" value="Cancelar"/>

                                
                            </f:facet>
                            
                        </h:panelGrid>

                    </p:dialog>


                </h:form> 


                <h:form id="formUpdate">

                    <p:dialog header="Modificar Usuario" widgetVar="dialogUsuarioUpdate"  resizable="false" id="dlgUsuarioUpdate" 
                              showEffect="fade"    hideEffect="explode"  modal="true" >

                        <h:panelGrid  id="display" columns="2"  cellpadding="4" style="margin:0 auto;" >

                            <h:outputText value="Codigo" />
                            <p:inputText  value="#{usuarioBean.selectedUsuario.codigo}"  />

                            <h:outputText value="Usuario" />
                            <p:inputText  value="#{usuarioBean.selectedUsuario.usuario}"  />

                            <h:outputText value="Senha" />
                            <p:inputText  value="#{usuarioBean.selectedUsuario.senha}"  />

                             <f:facet name="footer">
                          
                            <p:commandButton id="btnUsuarioAtualizar"  update=":formDataTable, :msgs" oncomplete=" dialogUsuarioUpdate.hide()" icon="icon-salvar" title="Atualizar" value="Atualizar"/>
                            <p:commandButton id="btnUsuarioCancelar"  styleClass="ui-confirmdialog-no"   oncomplete=" PF('dialogUsuarioUpdate').hide()"  icon="icon-cancelar" title="Cancelar" value="Cancelar"/>

                                
                            </f:facet>
                            
                            
                        </h:panelGrid>

                    </p:dialog>


                </h:form> 


                <h:form id="formDelete">

                  
                    <p:confirmDialog  global="true"  id="confirmDialog" 
                                      header="Excluir Usuário" 
                                      message="Você tem certeza que deseja excluir este usuário?"
                                      severity="alert" widgetVar="dialogUsuarioDelete"  >
                         
                        <p:commandButton  id="confirm" value="Sim " update=":msgs" oncomplete="dialogUsuarioDelete.hide()"
                                          actionListener="#{usuarioBean.btnDeleteUsuario}" icon="icon-ok"/>
                            
                        <p:commandButton id="Cancelar" value="Nao" styleClass="ui-confirmdialog-no"   onclick="dialogUsuarioDelete.hide()" type="button" icon="icon-cancelar" />
                        
                        
                        </p:confirmDialog>



                </h:form> 


            </ui:define>  

        </ui:composition>



    </body>


</html>

Tente colocar o form dentro do dialog, ao invés de deixar o dialog dentro do form. No PF5 vc terá que usar o appendTo="@(body)" no seu dialog.

                <p:dialog header="Incluir  Usuario" widgetVar="dialogUsuarioCriar"  resizable="false" id="dlgUsuarioCriar"   
                          showEffect="fade"    hideEffect="explode"  modal="true" >  

                    <h:form id="formCriar">  
                    <h:panelGrid  id="display" columns="2"  cellpadding="4" style="margin:0 auto;" >  

                        <h:outputText value="Codigo" />  
                        <p:inputText value="#{usuarioBean.selectedUsuario.codigo}" style="font-weight: bold" />  

                        <h:outputText value="Usuario" />  
                        <p:inputText  value="#{usuarioBean.selectedUsuario.usuario}" style="font-weight: bold" />  

                        <h:outputText value="Senha" />  
                        <p:inputText  value="#{usuarioBean.selectedUsuario.senha}" style="font-weight: bold" />  
                           
                        <f:facet name="footer">  
                        
                            <p:commandButton id="btnUsuarioSalvar"  update=":formDataTable, :msgs" oncomplete="dialogUsuarioCriar.hide()" actionListener="#{usuarioBean.btnCriarUsuario(actionEvent)}" icon="icon-salvar" title="Salvar" value="Salvar"/>  
                        <p:commandButton id="btnUsuarioCancelar"   oncomplete=" PF('dialogUsuarioCriar').hide()" icon="icon-cancelar" title="Cancelar" value="Cancelar"/>  

                              
                        </f:facet>  
                          
                    </h:panelGrid>  


            </h:form>   
                </p:dialog>

Opa fiz assim do jeito que você sugeriu só não entendi essa parte do appendTo="@(body)" como devo colocar assim,porém não funcionou.

   <p:dialog appendTo="@(body)"  header="Incluir  Usuario" widgetVar="dialogUsuarioCriar"  resizable="false"          id="dlgUsuarioCriar" 
                              showEffect="fade"    hideEffect="explode"  modal="true" >
                       <h:form id="formCriar">

Também tentei sem a propriedade appendTo="@(body)" ,mas não apareceu nenhuma mensagem e nem gravou no banco.


 <p:dialog  header="Incluir  Usuario" widgetVar="dialogUsuarioCriar"  resizable="false" id="dlgUsuarioCriar" 
                              showEffect="fade"    hideEffect="explode"  modal="true" >
                       <h:form id="formCriar">
                        <h:panelGrid  id="display" columns="2"  cellpadding="4" style="margin:0 auto;" >

                            <h:outputText value="Codigo" />
                            <p:inputText value="#{usuarioBean.selectedUsuario.codigo}" style="font-weight: bold" />

                            <h:outputText value="Usuario" />
                            <p:inputText  value="#{usuarioBean.selectedUsuario.usuario}" style="font-weight: bold" />

                            <h:outputText value="Senha" />
                            <p:inputText  value="#{usuarioBean.selectedUsuario.senha}" style="font-weight: bold" />
                             
                            <f:facet name="footer">
                          
                                <p:commandButton id="btnUsuarioSalvar"  update=":formDataTable, :msgs" oncomplete="dialogUsuarioCriar.hide()" actionListener="#{usuarioBean.btnCriarUsuario(actionEvent)}" icon="icon-salvar" title="Salvar" value="Salvar"/>
                            <p:commandButton id="btnUsuarioCancelar"   oncomplete=" PF('dialogUsuarioCriar').hide()" icon="icon-cancelar" title="Cancelar" value="Cancelar"/>

                                
                            </f:facet>
                            
                        </h:panelGrid>
                        </h:form> 
                    </p:dialog>