[jbossseam-issues] [JBoss JIRA] Commented: (JBSEAM-880) Make UISelectItems more permissive to null-values

Guy Veraghtert (JIRA) jira-events at lists.jboss.org
Mon Feb 19 08:56:31 EST 2007


    [ http://jira.jboss.com/jira/browse/JBSEAM-880?page=comments#action_12353520 ] 
            
Guy Veraghtert commented on JBSEAM-880:
---------------------------------------

Interesting discussion. How about following case ? (details left out)

<h:selectOneMenu value="#{bean.parent}" valueChangeListener="#{...}">
  <s:selectItems value="#{allParents}" noSelectionLabel="[Please select]"/>
</h:selectOneMenu>

<h:selectOneMenu value="#{bean.child}" disabled="#{empty bean.parent}">
  <s:selectItems value="#{bean.parent.children}" noSelectionLabel="[Please select]"/>
</h:selectOneMenu>

You have a screen with two dropdowns, the second isn't enabled until a selection is made in the first one and allows you to choose one of the selected parent's children. With the current implementation of UISelectItems, a dummy Parent must be returned by the getParent() method on bean, not an existing one, otherwise that parent will be pre-selected in the first dropdown, which we don't want.
If we don't provide this dummy parent, an exception will occur, because bean.parent evaluates to null and hence also bean.parent.children, although a parent instance getChildren() method always returns a non-null value.

When adding an empty list the user woudn't see an empty dropdown, but a disabled one, with [Please Select] as the first value.

So, I would opt for the alternative with the empty list and a WARN message ;-), as you could have guessed. (However, be careful that the log statement doesn't cause another exception)

> Make UISelectItems more permissive to null-values
> -------------------------------------------------
>
>                 Key: JBSEAM-880
>                 URL: http://jira.jboss.com/jira/browse/JBSEAM-880
>             Project: JBoss Seam
>          Issue Type: Patch
>          Components: JSF
>    Affects Versions: 1.1.7.GA
>            Reporter: Guy Veraghtert
>         Assigned To: Peter Muir
>            Priority: Minor
>             Fix For: 1.1.7.GA
>
>         Attachments: patch-880.txt
>
>
> The method createSelectItems(Object value) in UISelectItems is not permissive to null-values; a framework class should not die on NPE.
> This can be fixed by assigning an empty list to value when value == null

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