[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_12414234 ] 
            
Dan Allen commented on JBSEAM-2469:
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I'm not sure if I can make this explanation make sense, but what you are proposing is exactly what I have proposed. Here goes.

The very presence of the javax.faces.ViewState param in the request identifies it as a postback (the UI component tree is restored). There is no need storing a flag in the page context since we already know it is a postback then for that page. If you disable the page action on postback, as I am proposing, then it would be impossible for the page action to execute twice as long as you continue to postback to the same page (perform any sort of JSF action on the page).

Now, if you were to navigate after a postback, either to the same page (redirect) or another page, then it ceases to be classified as a postback at that point. Thus, the page action will once again be executed for whatever page you are navigating to, again the behavior you desire.

Trust that what you are asking for is what we plan to implement. Now, if you want to disable the page action even on a followup initial request (let's say as part of the same conversation), then you have to do using your own business logic combined with the "if" attribute on the <action> element.

> 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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