[jira] [Commented] (WICKET-6451) Real Exception while setting model object is hidden

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

    [ https://issues.apache.org/jira/browse/WICKET-6451?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16131826#comment-16131826 ] 

Sven Meier commented on WICKET-6451:
------------------------------------

We could improve support for different collection types. For this Wicket will have to create a suitable collection, e.g. in a new method in Objects:

{code}
/**
 * Creates a new collection. 
 * 
 * @param hint type deciding the type of the returned collection 
 * @return collection
 * @throws IllegalArgumentException if type is not supported
 */
public static <S> Collection<S> newCollection(Class<?> hint)
{
	if (Set.class.isAssignableFrom(hint)) {
		return new HashSet<>();
	} if (List.class.isAssignableFrom(hint)) {
		return new ArrayList<>();
	} else {
		throw new IllegalArgumentException("unsupported type '" + hint + "'");
	}
}
{code}

> Real Exception while setting model object is hidden
> ---------------------------------------------------
>
>                 Key: WICKET-6451
>                 URL: https://issues.apache.org/jira/browse/WICKET-6451
>             Project: Wicket
>          Issue Type: Improvement
>          Components: wicket
>    Affects Versions: 8.0.0-M6
>            Reporter: Kamil
>            Assignee: Sven Meier
>            Priority: Minor
>         Attachments: showcase-hiddenException.zip
>
>
> When object returns Collections.unmodifiableSet() it is obvious that model object can not be updated.
> But the exception that was thrown causes me to spend hours until I found out that:
> {code}
> Last cause: Could not convert value: [] to type: java.util.Set. Could not find compatible converter.
> WicketMessage: An error occurred while trying to set the collection attached to [BootstrapMultiSelect [Component id = children]]
> {code}
> Is not about converter but about unmodifialble set, because the real exception was hidden!
> 1)Run the app
> 2)Click submit
> 3)Caused by User#L30



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