Norbert Truchsess wrote:
> in
> com.sun.faces.taglib.jsf_core.ActionListenerTag.BindingActionListener
> we have:
>
> private static class BindingActionListener
> implements ActionListener, Serializable {
> private transient ActionListener instance;
>
> ...
>
> public void processAction(ActionEvent event) throws
> AbortProcessingException {
> if (instance == null) { // <------ depends on way of
> statesaving!
> instance = (ActionListener)
> Util.getListenerInstance(type, binding);
> }
> if (instance != null) {
> instance.processAction(event);
> } else {
> if (logger.isLoggable(Level.WARNING)) {
> logger.log(Level.WARNING,
>
> "jsf.core.taglib.action_or_valuechange_listener.null_type_binding",
> new Object[] {
> "ActionListener",
>
> event.getComponent().getClientId(FacesContext.getCurrentInstance())});
> }
> }
> }
>
> Since 'instance' is marked as transient, it will not undergo
> serialization and
> thus will be null on postback after state is restored in case of
> client-side
> statesaving. If statesaving is set to server, no serialization takes
> place so
> BindingActionListener would return the old reference to instance on
> postback.
>
> This is inconsistend behaviour.
>
> And if the Listener e.g. happens to be a request-scoped managed bean
> returning
> the old reference instead of re-evaluating the expression on postback
> will
> return the reference to the outdated instance (which is very bad!)
>
> Same issue with 'transient XXXXXListener instance' is being found in both
> com.sun.faces.taglib.jsf_core.PhaseListenerTag.BindingPhaseListener and
> com.sun.faces.taglib.jsf_core.ValueChangeListenerTag.BindingValueChangeListener
>
>
> I've filed Issue # 656 against the RI:
> https://javaserverfaces.dev.java.net/issues/show_bug.cgi?id=656
Thanks for the report.
>
> On the other hand the spec says:
>
> 'If binding is set, create a ValueExpression by invoking
> Application.createValueExpression() with binding as the expression
> argument,
> and Object.class as the expectedType argument. Use the ValueExpression
> to obtain
> a reference to the ActionListener instance. If there is no exception
> thrown, and
> ValueExpression.getValue() returned a non-null object that implements
> javax.faces.event.ActionListener, register it by calling
> addActionListener().
> If there was an exception thrown, rethrow the exception as a
> JspException.'
>
> According to the spec the instance returned by evaluation of the
> binding-expression would have to be used. It doesn't mention that it's
> legal to use a lazy-loading wrapper for optimization.
This has been brought up in the past and the spec leads agreed the
lazy-binding is the proper way of handing it and would incorporate
the appropriate changes into the spec.
> But if we wouldn't use a lazy-loading wrapper, it wouldn't be possible
> to reevaluate the binding-expression on postback at all. From my point
> of view this is also a spec-bug - the spec should either specify that
> it has to be exactly the single instance of Listener that is to be
> used, or the binding-expression would have to be reevaluated on every
> access (as this is done with deferred expressions in
> UIComponent-attributes getter-methods).
>
> I've filed a spec bug for this as well:
> https://javaserverfaces-spec-public.dev.java.net/issues/show_bug.cgi?id=320
>
>
>
> - Norbert Truchsess
>
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