ManagedBean is constructed but shouldn't? - jsf

Question

I'working on a enterprise application that uses JSF 2.0, with Netbeans 7.0 and Glassfish 3.1
I have a managed bean that is ViewScoped. this is the declaration of the class:
#ManagedBean(name = "myBean")
#ViewScoped
public class MyMBean implements Serializable {
Inside its #PostConstruct, it has the following:
String id = FacesContext.getCurrentInstance().getExternalContext().getRequestParameterMap().get("id");
if (id == null) {
try {
FacesContext.getCurrentInstance().getExternalContext().redirect("home.xhtml");
FacesContext.getCurrentInstance().responseComplete();
} catch (Exception e) { }
return;
}
if I go to the page that uses this managed bean, and the id is null, everything works fine, and I get redirected to home page.
The problem is that when I navigate to a different page that does NOT use this managed bean (lets say for example "otherpage.xhtml") the PostConstruct method is executed, and it shouldn't! And it gets worse: since the url of this other page doesn't have the "id" parameter, the bean tries to redirect to home page; and I get a IllegalStateException.
Any idea of why a viewscoped managed bean is constructed when navigating to a page that does not use it?
Edit:
If in order to navigate to "otherpage.xhtml" I use the commandlink in "home.xhtml", 6 extra beans are created.
But, if instead of using the link, I type the url in the browser; it works fine. No extra bean is created. Maybe there's something wrong in how I implemented the link. This is the code:
<h:form>
<h:commandLink value="Go to other page" action="otherPage" />
</h:form>
And this is the navigation rule in faces-config:
<navigation-rule>
<from-view-id>*</from-view-id>
<navigation-case>
<from-outcome>otherPage</from-outcome>
<to-view-id>/views/otherPage.xhtml</to-view-id>
<redirect/>
</navigation-case>
</navigation-rule>
Is there anything wrong there?
Thanks!
Damian

Answer 1

You surely have a #{myBean} somewhere in the view or one of its templates/include/tag/composite files, or as a #ManagedProperty of the beans referenced by the view. Putting a breakpoint in the (post)constructor and investigating the stacktrace should give enough insights who/what has triggered the bean's construction.
Unrelated to the concrete problem, the ExternalContext#redirect() already implicitly calls FacesContext#responseComplete(), you don't need to call it yourself. See also the method's javadoc.
Update: a <h:commandLink> submits its parent POST <form> to the current page (and thus creates all its related beans!) and then depending on the navigation outcome, it will forward/redirect to the result page. You shouldn't be using commandlinks/commandbuttons for plain page-to-page navigation. Use <h:link> instead.
<h:link value="Go to other page" outcome="views/otherPage" />
You can eventually also get rid of that <navigation-case>. If you really insist in keeping that navigation case, then use outcome="otherPage" instead.
See also:
When should I use h:outputLink instead of h:commandLink?
Communication in JSF 2.0 - Implicit navigation