Erin Schnabel wrote:
I've seen a few of these, and it doesn't really have anything to do with the $xwiki reference (though perhaps the code should be changed to avoid that misleading message..). The original cause is an NPE originating out of Collections.sort, which is called by XWiki.sort:
XWiki.sort:
public List sort(List list) { Collections.sort(list); return list; }
Collections.sort doesn't appear to check for null:
public static <T extends Comparable<? super T>> void sort(List<T> list) { Object[] a = list.toArray(); Arrays.sort(a);
Seems to me like your panel needs to make sure your list is non-null (not empty) before calling xwiki.sort
Thanks for taking the time to answer me! I see the flaw that you pointing out.
The recommended (from the velocity docs) way to check for non-null && not empty:
#if( "$!allTags" != '') #set( $allTagsSorted = $xwiki.sort($allTags)) #end
That should solve the problem.
I ended up doing something similar: #set( $allTags = $xwiki.search($query)) #if ( $allTags.size() > 1) ...do stuff #end However, I'm absolutely positive that my list of tags isn't empty, so this can't the ultimate cause of the problem. This was confirmed by Sergiu Dumitriu; he recently updated the jira issue concerning the inclusion of the above mentioned tag cloud in xwiki. Check it out: http://jira.xwiki.org/jira/browse/XE-51 cheers :-) Thomaas