[jbossseam-issues] [JBoss JIRA] Commented: (JBSEAM-2469) add postback flag to page actions

[Dan Allen (JIRA)]

    [ http://jira.jboss.com/jira/browse/JBSEAM-2469?page=comments#action_12414252 ] 
            
Dan Allen commented on JBSEAM-2469:
-----------------------------------

Ah, I need to clarify a bit because I see that if I am getting my facts mixed up.

#1) If your navigation rule uses <render> and that view ID is different than the current view ID, then a new UI component tree is created. That clears any prior page context variables. However, page actions are *not* executed in this case (because it is not a top-level request). Page actions are only executed on a new request (regardless of it being a GET or POST).

#2) If your navigation rule uses <redirect>, regardless of whether the view ID is the same or different, a new request is issued. As a result, a new UI component tree is created, any prior page context variables are cleared out, and page actions *do* execute. Unfortunately, there is no way to know (short of using request parameters) that this request (after the redirect) has any relation to a postback. (Ah, except the temporary conversation, which does survive the redirect. So perhaps you could stuff something into the conversation scope).

So if you are always using <redirect>, then yes, your page actions are going to be invoked even if you have the postback disabled flag (which is not yet developed). I'm not sure you are going to get support from Seam here. You need to make your page actions aware of this situation. My suggestion is to outject something to the conversation scope and then check for it in your page action. Conversations (even if they are temporary) do survive the redirect.

You can check for a temporary conversation by using #{manager.currentConversationEntry.removeAfterRedirect}

> add postback flag to page actions
> ---------------------------------
>
>                 Key: JBSEAM-2469
>                 URL: http://jira.jboss.com/jira/browse/JBSEAM-2469
>             Project: Seam
>          Issue Type: Feature Request
>          Components: Core
>    Affects Versions: 2.0.1.CR1
>            Reporter: Dan Allen
>         Assigned To: Dan Allen
>             Fix For: 2.1.0.BETA2
>
>   Original Estimate: 1 hour
>  Remaining Estimate: 1 hour
>
> Page actions are incredibly useful, but sometimes they can get in the way during a postback. I would like to see a postback attribute added to the <action> tag that can be used to disable the action on postback. It's possible using a conditional, but it is ugly and a lot of typing.
> Here is the logic that would go into Pages.java
>     private boolean isPostBack(FacesContext facesContext)
>     {
>         return facesContext.getExternalContext().getRequestParameterMap().
>               containsKey(ResponseStateManager.VIEW_STATE_PARAM);
>     }
> The conditional alternative would be:
> <action execute="#{component.action}" if="#{empty param['javax.faces.ViewState']}"/>

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