Calling HttpServletRequest authenticate() from preRenderView listener

Question

Hi,
I'm trying to use the authenticate() in a preRenderView listener method, in order to trigger authentication conditionally, depending on view parameters in the page. I tried adding a simple method:
@Named
@RequestScoped
public class PermissionBean implements java.io.Serializable {
public void preRender() {
System.out.println("IN PRERENDER");
HttpServletRequest request = (HttpServletRequest)FacesContext.getCurrentInstance().getExternalContext().getRequest();
HttpServletResponse response = (HttpServletResponse)FacesContext.getCurrentInstance().getExternalContext().getResponse();
try {
request.authenticate(response);
} catch (Exception e) {  // may throw ServletException or IOException
e.printStackTrace();
The authenticate method itself doesn't throw an exception, it triggers the redirect to Login.xhtml as expected. However, I'm getting in my server log, I get this exception:
INFO: IN PRERENDER
FINEST: GET /Login.xhtml previous[3]
INFO: Exception when handling error trying to reset the response.
java.lang.NullPointerException
     at com.sun.faces.facelets.tag.jsf.core.DeclarativeSystemEventListener.processEvent(EventHandler.java:126)
     at javax.faces.component.UIComponent$ComponentSystemEventListenerAdapter.processEvent(UIComponent.java:2508)
     at javax.faces.event.SystemEvent.processListener(SystemEvent.java:106)
     at com.sun.faces.application.ApplicationImpl.processListeners(ApplicationImpl.java:2129)
     at com.sun.faces.application.ApplicationImpl.invokeComponentListenersFor(ApplicationImpl.java:2077)
     at com.sun.faces.application.ApplicationImpl.publishEvent(ApplicationImpl.java:286)
     at com.sun.faces.application.ApplicationImpl.publishEvent(ApplicationImpl.java:244)
     at javax.faces.application.ApplicationWrapper.publishEvent(ApplicationWrapper.java:670)
     at com.sun.faces.lifecycle.RenderResponsePhase.execute(RenderResponsePhase.java:108)
     at com.sun.faces.lifecycle.Phase.doPhase(Phase.java:101)
     at com.sun.faces.lifecycle.LifecycleImpl.render(LifecycleImpl.java:139)
     at javax.faces.webapp.FacesServlet.service(FacesServlet.java:594)
So my request is not redirected to Login.xhtml.
My question is - is this something that should work within a JSF managed bean, or is it only legal outside of JSF request lifecycle? I tried calling authenticate() from a WebFilter, and it works as exptected.
Thanks,
Ellen

Answer 1

I also posted this question on StackOverflow, and got an answer, which is that I have to set responseComplete() in order for the redirect to the Login page to work:
http://stackoverflow.com/questions/7015516/problem-using-httpservletrequest-authenticate-within-jsf-2-0-prerenderview-list
Unfortunately, this doesn't work, because after authenticate() is called, FacesContext.getCurrentInstance() returns null.
Edited by: 878628 on Aug 31, 2011 8:50 AM