Can't seem to redirect from a ViewScoped constructor.

Question

I'm having trouble redirecting from a view scoped bean in the case that we don't have the required info for the page in question. The log entry in the @PostContruct is visible in the log right before a NPE relating to the view trying to render itself instead of following my redirect. Why is it ignoring the redirect?

Here's my code:

@ManagedBean
public class WelcomeView {

    private String sParam;
    private String aParam;

    public WelcomeView() {
        super();

        sParam = getURL_Param("surveyName");
        aParam = getURL_Param("accountName");

        project = fetchProject(sParam, aParam);

    }

    @PostConstruct
    public void redirectWithoutProject() {
        if (null == project) {
            try {
                logger.warn("NO project [" + sParam + "] for account [" + aParam + "]");
                FacesContext fc = FacesContext.getCurrentInstance();
                fc.getExternalContext().redirect("/errors/noSurvey.jsf");
                return;
            } catch (Exception e) {
                e.printStackTrace();
            }
        }        
    }

    ....

    public boolean getAuthenticated() {
        if (project.getPasswordProtected()) {
            return enteredPassword.equals(project.getLoginPassword());
        } else return true;
    }

}

Here's the stack trace:

SEVERE: Error Rendering View[/participant/welcome.xhtml]
javax.el.ELException: /templates/participant/welcome.xhtml @80,70 rendered="#{welcomeView.authenticated}": Error reading 'authenticated' on type com.MYCODE.general.controllers.participant.WelcomeView
    at com.sun.faces.facelets.el.TagValueExpression.getValue(TagValueExpression.java:107)
    at javax.faces.component.ComponentStateHelper.eval(ComponentStateHelper.java:190)
    at javax.faces.component.UIComponentBase.isRendered(UIComponentBase.java:416)
    at javax.faces.component.UIComponent.encodeAll(UIComponent.java:1607)
    at javax.faces.component.UIComponent.encodeAll(UIComponent.java:1616)
    at javax.faces.render.Renderer.encodeChildren(Renderer.java:168)
    at javax.faces.component.UIComponentBase.encodeChildren(UIComponentBase.java:848)
    at javax.faces.component.UIComponent.encodeAll(UIComponent.java:1613)
    at javax.faces.component.UIComponent.encodeAll(UIComponent.java:1616)
    at javax.faces.component.UIComponent.encodeAll(UIComponent.java:1616)
    at com.sun.faces.application.view.FaceletViewHandlingStrategy.renderView(FaceletViewHandlingStrategy.java:380)
    at com.sun.faces.application.view.MultiViewHandler.renderView(MultiViewHandler.java:126)
    at com.sun.faces.lifecycle.RenderResponsePhase.execute(RenderResponsePhase.java:127)
    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:313)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
    at com.MYCODE.general.filters.StatsFilter.doFilter(StatsFilter.java:28)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:233)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191)
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:433)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:128)
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102)
    at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:568)
    at org.apache.catalina.authenticator.SingleSignOn.invoke(SingleSignOn.java:421)
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:286)
    at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:845)
    at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:583)
    at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:447)
    at java.lang.Thread.run(Thread.java:637)
Caused by: java.lang.NullPointerException
    at com.MYCODE.general.controllers.participant.WelcomeView$$M$863c205f.getAuthenticated(WelcomeView.java:127)
    at com.MYCODE.general.controllers.participant.WelcomeView$$A$863c205f.getAuthenticated(<generated>)
    at com.MYCODE.general.controllers.participant.WelcomeView.getAuthenticated(WelcomeView.java:125)
    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 javax.el.BeanELResolver.getValue(BeanELResolver.java:62)
    at javax.el.CompositeELResolver.getValue(CompositeELResolver.java:53)
    at com.sun.faces.el.FacesCompositeELResolver.getValue(FacesCompositeELResolver.java:72)
    at org.apache.el.parser.AstValue.getValue(AstValue.java:118)
    at org.apache.el.ValueExpressionImpl.getValue(ValueExpressionImpl.java:186)
    at com.sun.faces.facelets.el.TagValueExpression.getValue(TagValueExpression.java:102)
    ... 33 more

Answer 1

Isn't the enteredPassword just null? The stacktrace tells that it's the 2nd line in the method body (line 127 while method starts at line 125), so project which is already accessed in 1st line is not null.

At any way, if the redirect wasn't possible, then you should have noticed an IllegalStateException in the stacktrace which is telling why it isn't able to redirect (e.g. Response already committed).

Answer 2

SOLVED! The problem was that I didn't realise the page would be fully compiled regardless of my redirect, thus the null project was in fact a problem. The call to getAuthenticated (which should actually be isAuthenticated, but this doesn't cause any real trouble) failed as project is null (as expected) and my logic was that this shouldn't be called if the redirect happens in the constructor. This is lies. The redirect may be called in the constructor, but the bean and the view are both constructed before the redirect actually happens.