jsf 2 - How to perform navigation in preRenderView listener method

Question

I'm starting from What can <f:metadata>, <f:viewParam> and <f:viewAction> be used for?

I have a pre render view event listener:

<f:metadata>
    <f:event type="preRenderView" listener="#{loginBean.performWeakLogin()}" />
</f:metadata>

which invokes the following method:

public String performWeakLogin() {
    FacesContext facesContext = FacesContext.getCurrentInstance();
    String parameter_value = (String) facesContext.getExternalContext().getRequestParameterMap().get("txtName");

    if (parameter_value != null && parameter_value.equalsIgnoreCase("pippo")) {
        try {
            return "mainPortal";
        } catch (IOException ex) {
            return null;
        }
    } else {
        return null;
    }
}

and the following navigation rule:

<navigation-rule>
    <from-view-id>/stdPortal/index.xhtml</from-view-id>
    <navigation-case>
        <from-outcome>mainPortal</from-outcome>
        <to-view-id>/stdPortal/stdPages/mainPortal.xhtml</to-view-id>
        <redirect/>
    </navigation-case>
</navigation-rule>

However, it doesn't perform the navigation. It works when I use a command button as follows:

<p:commandButton ... action="#{loginBean.performWeakLogin()}"  /> 

Answer 1

Navigation based on a method's return value is only performed by components implementing ActionSource2 interface and providing an attribute taking a MethodExpression for that, such as action attribute of UICommand components, which is queued during Apply Request Values phase and invoked during Invoke Application phase.

The <f:event listener> is merely a component system event listener method, not an action method. You need to perform the navigation manually as follows:

public void performWeakLogin() {
    // ...

    FacesContext fc = FacesContext.getCurrentInstance();
    fc.getApplication().getNavigationHandler().handleNavigation(fc, null, "mainPortal");
}

Alternatively, you can also send a redirect on a given URL, which is more useful for the case you don't want to navigate internally, but externally:

public void performWeakLogin() throws IOException {
    // ...

    ExternalContext ec = FacesContext.getCurrentInstance().getExternalContext();
    ec.redirect(ec.getRequestContextPath() + "/stdPortal/stdPages/mainPortal.xhtml");
}

---

Unrelated to the concrete problem, a servlet filter is a better place for the job of performing request based authorization/authentication.

See also:

• Is there any easy way to preprocess and redirect GET requests?