<p:selectOneMenu filter="true" filterMatchMode="contains" converter="omnifaces.SelectItemsConverter" value="#{requestBean.manager}" required="true">
        <f:selectItems value="#{userBean.userList}" var="label" />
</p:selectOneMenu>

@ManagedBean
@SessionScoped
public class RequestBean{
RequestUser manager;

public void onleoad(){

manager = new RequestUser();}

 public void addRequest() throws IOException, MessagingException, NamingException{

  manager = (RequestUser) FacesContext.getCurrentInstance().getExternalContext().getSessionMap().get("manager");}