JSF 2 @ViewScoped doesn't call @PreDestroy method

Question

howdy guys!
i've been tested the jsf ViewScoped in my application but i have a doubt. The managed bean noted with @ViewScoped sometimes does not call the @PreDestroy method.
See example below
ViewScopeMB.java
@ManagedBean
@ViewScoped
public class ViewScopeMB implements Serializable {
private int counter;
public ViewScopeMB() { }
@PostConstruct
public void contruct() {
System.out.println("iniciando bean");
this.counter = 0;
// getters and setters
public void increment() {
System.out.println("incrementing...");
this.counter++;
public void forceSetView() {
System.out.println("modificando a viewroot");
FacesContext context = FacesContext.getCurrentInstance();
UIViewRoot root = context.getApplication().getViewHandler().createView(context, "/faces/one.xhtml");
context.setViewRoot(root);
@PreDestroy
public void destroy() {
System.out.println("destroy the bean");
I'm using f:ajax to incrementing the counter and this work fine, the bean instance is kept, but when i navigate for new page using <a:href for exemple the ViewScopeMB instance is not destroyed. I change my link to <h:commandLink action="rule"... and the @PreDestroy method is called and the finalize method too.
My question is, this is a correct behavior of JSF 2? If the user use the navigator back button or to type the new url or the button with javascript history.go(-1) my instance of ViewScopeMB will never be destroyed in the user session?
When i used forceSetView() method to force a new viewRoot the @PreDestroy is called.
There are way to solve this case?
Sorry if i not been very clear.
Anybody help-me?

Answer 1

For a view scoped bean, PreDestroy must only be called when the view scope is destroyed which happens when something calls FacesContext.setViewRoot(root).
It's not very surprising that when you don't use JSF controls for navigation then context.setViewRoot(root);is not called.
Calling context.setViewRoot(root); yourself guarantees that PreDestroy gets called but you'll probably end up calling it more times than you need to in the cases where you use JSF navigation mechanisms.
You should be careful with that @PreDestroy method though. Some containers e.g (Tomcat) don't always support those methods fully. In particular, @PreDestroy methods are not called when the view gets destroyed after a restart when the webserver had serialized the ViewScoped bean in the current view so I wouldn't be putting billion dollars worth of logic in that method.