Viewscoped bean states preserved differently in Mojarra and MyFaces

Question

I have a view where you can start an expensive process. The view is paired to a @ViewScoped bean, and if the process is started, the status is checked periodically with PrimeFaces's . I have the following Runnable which calls a webservice with an expensive operation.

public class Generator extends AsyncCaller {

    private Viewer bean;
    private String id;

    public Generator(Viewer bean, Client client, String id) {
        super(client);
        this.bean = bean;
        this.id = id;
    }

    @Override
    public void run() {
        ClientResponse response = getClient().generate(this.id); 

        boolean error =
(response.getClientResponseStatus().getFamily() != Family.SUCCESSFUL);
        if (error) {
            Exception e = new UniformInterfaceException(response);
            this.bean.setGenerateException(e);
        }
        this.bean.setGenerateError(error);
    }

}

I start this Runnable as a separate Thread, so the UI is not blocked. As you can see I pass the view scoped managed bean instance to the Runnable so if there is an error I can set it in the bean and later show it on the UI.

My problem is that with Mojarra 2.1.6 and 2.1.26 this works fine, but with MyFaces 2.1.13 – which I would prefer to use – the generateError variable is never true in the bean, although I can see setGenerateError(true) called in debug. The actual bean that is used with the view is different from the bean instance that is accessible from the thread. I can actually see this in debug: with MyFaces, every poll request results in a new view scoped bean instance, whereas with Mojarra it is always the same instance.

Is there a <context-param /> setting in MyFaces that I am missing? Which one is actually the correct behaviour as per specification?

Answer 1

Found the answer in the OmniFaces showcase's web.xml:

<context-param>
    <!-- MyFaces and Mojarra don't agree on the default setting for actually 
        serializing state in the session as opposed to just storing a reference. 
        Mojarra's default is false, but can be switched to true. MyFaces' default 
        is true, and can be switched to false, which we thus do below. See http://arjan-tijms.omnifaces.org/p/jsf-22.html#1127 -->
    <param-name>org.apache.myfaces.SERIALIZE_STATE_IN_SESSION</param-name>
    <param-value>false</param-value>
</context-param>