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

[Dan Allen (JIRA)]

     [ https://jira.jboss.org/jira/browse/JBSEAM-2469?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Dan Allen resolved JBSEAM-2469.
-------------------------------

    Fix Version/s: 2.0.3.CR2
       Resolution: Done
           Labels: page-action postback  (was: )


I decided to keep the implementation simple by giving the developer a flag to disable the page action during a standard JSF postback. The spirit of page actions from day 1 was to provide a way to execute an action on an initial GET request. Typically, you don't need this behavior during a postback because you have at least a dozen other ways to perform work (and lots of information to do it with).

To maintain backwards compatibility (and generally just be polite), page actions will execute on any request by default. If you want to disable the action during a JSF postback, you would define the action as follows:

<execute action="#{componentName.prepareData}" on-postback="false"/>

For those of you that requested more features, I want to remind you that the "if" attribute gives you tremendous flexibility. And you can set any context variable you want during a page action which you can then reference to disable it on a subsequent request if the basic use case here doesn't fit your needs. We cannot design the framework to fill individual needs or else it would become a tangled ball of mess.

> add postback flag to page actions
> ---------------------------------
>
>                 Key: JBSEAM-2469
>                 URL: https://jira.jboss.org/jira/browse/JBSEAM-2469
>             Project: Seam
>          Issue Type: Feature Request
>          Components: Core
>    Affects Versions: 2.0.1.CR1
>            Reporter: Dan Allen
>            Assignee: Dan Allen
>             Fix For: 2.0.3.CR2, 2.1.0.CR1
>
>   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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