Command Navigation Item + Filter mapping issue

Question

Readers,
I have 2 questions here
1) How is navigation item different from commandLink ?
2)I am having a navigation item in my Main Page. the code of which is
<f:facet name="globalLinks">
            <af:group id="g1">
              <af:spacer width="10" height="10" id="s1"/>
              <af:navigationPane id="np1" hint="bar"
                                 inlineStyle="vertical-align:sub;">
                <af:commandNavigationItem text="Home" id="cni2"
                                          icon="/com/xxx/images/home.gif"
                                          destination="/faces/MainPage"
                                          targetFrame="_self"/>
                <af:commandNavigationItem text="Logout" id="cni1"
                                          icon="/com/xxx/images/glbl_logout.gif"
                                          actionListener="#{backingBeanScope.MainPageBean.doLogout}"/>
              </af:navigationPane>
            </af:group>
          </f:facet>I have configured a filter to intercept all URL of type "/*" and redirect it tologin page if the session attribute is null
the issue happening here is on click of the Home link, it takes me to the login page in spite of configuring the commandNavigationItem for home link (see the above code). When i click on logout though i am redirected to login page i get the NPE.
Code for Filter is
                if (session.getAttribute("userLoginId") != null) {
                    user = (String)session.getAttribute("userLoginId");
                if ((user == null) || (user.equals(""))) {
                    String finalRedirectURL =  "/Portal/faces/LoginPage";
                    hres.sendRedirect(finalRedirectURL);
                    FacesContext context = FacesContext.getCurrentInstance();
                    context.responseComplete();  //*on logout i get NPE here*
                }Please advice..
thnks
Jdev 11.1.1.5

Answer 1

Question one still unanswered also a bit of question 2.
Now the issue is getting the following error on logout, clicking on home page now doesn't redirect me to login page.
java.lang.IllegalStateException: Cannot forward a response that is already committed
     at weblogic.servlet.internal.RequestDispatcherImpl.forward(RequestDispatcherImpl.java:122)
     at com.sun.faces.context.ExternalContextImpl.dispatch(ExternalContextImpl.java:410)
     at org.apache.myfaces.trinidad.context.ExternalContextDecorator.dispatch(ExternalContextDecorator.java:44)
     at org.apache.myfaces.trinidad.context.ExternalContextDecorator.dispatch(ExternalContextDecorator.java:44
Any ideas ?
Edited by: in the line of fire on Nov 1, 2011 1:18 PM