[jira] [Resolved] (WICKET-6403) DropDownChoice ignores OnChangeAjaxBehavior while setting null value when required is true

["Sven Meier (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/WICKET-6403?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Sven Meier resolved WICKET-6403.
--------------------------------
    Resolution: Invalid
      Assignee: Sven Meier

I've added some javadoc to #onUpdate.

Thanks!

> DropDownChoice ignores OnChangeAjaxBehavior while setting null value when required is true
> ------------------------------------------------------------------------------------------
>
>                 Key: WICKET-6403
>                 URL: https://issues.apache.org/jira/browse/WICKET-6403
>             Project: Wicket
>          Issue Type: Bug
>    Affects Versions: 8.0.0-M6
>            Reporter: Kamil
>            Assignee: Sven Meier
>
> I have a simple DropDown with OnChangeAjaxBehavior:
> {code}
> List<String> choices = Arrays.asList("one", "two", "three");
> IModel<String> wicketModel = Model.of();
> DropDownChoice<String> wicketDropDown = new DropDownChoice<>("wicketDropDown",wicketModel , ListModel.of(choices));
> wicketDropDown.add(new OnChangeAjaxBehavior() {
> 	@Override
> 	protected void onUpdate(AjaxRequestTarget target) {
> 		System.out.println("Wicket change: "+wicketModel.getObject());
> 	}
> });
> add(wicketDropDown);
> {code}
> onUpdate is called everytime I change the value *even if this value is "null value"*.
> Now when instead of:
> {code}
> add(wicketDropDown);
> {code}
> I set:
> {code}
> add(wicketDropDown.setRequired(true));
> {code}
> onUpdate works on selecting values but *does not work when selecting "null value"* which is wrong. 
> One of the use cases why it is wrong: I have two dropdowns. First dropdown selects _Group_ and second selects _Subgroup_. _Subgroup_ can not be selected if _Group_ is null, though if I select _Group_, then I select _Subgroup_ and then clear the _Group_ - _Subgroup_ should be cleared as well (but I'm not able to do that because onUpdate is not being called).



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