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https://issues.apache.org/jira/browse/WICKET-3972?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13088257#comment-13088257
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Sergiy Barlabanov commented on WICKET-3972:
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thanks for the fix. Will wait till RC6 :).
Though I think, that making Markups immutable would be a more clean solution
(requiring more code ;)). There is no real need to reassign tag ids on every
page/component render. The mutability of markup is a potential source of future
errors, since component markups and ComponentTag objects contained inside are
reused multiple times in different requests resulting in race conditions like
the one described in this bug report.
> wicket:message attribute results in "The component was rendered already" error
> ------------------------------------------------------------------------------
>
> Key: WICKET-3972
> URL: https://issues.apache.org/jira/browse/WICKET-3972
> Project: Wicket
> Issue Type: Bug
> Components: wicket-core
> Affects Versions: 1.5-RC5.1
> Environment: Linux Ubuntu, Tomcat 6, Java 6
> Reporter: Sergiy Barlabanov
> Assignee: Juergen Donnerstag
> Fix For: 1.5-RC6
>
> Attachments: quickstart.zip, wicket-message-index.patch
>
>
> Seems like there is a problem with generation of tag and component IDs when
> using wicket:message as an attribute for tags inside ListView.
> The quickstart webapp is attached to this ticket. There are two pages in this
> webapp: HomePage with a ListView containing tags with wicket:message
> attribute and two tags with wicket:message attribute outside the ListView. If
> a user goes to the next page (SecondPage) using the link on HomePage and then
> goes back to HomePage using the link on SecondPage, the exception mentioned
> in the subject occurs.
> Seems that the ID generation for tags and components is wrong: the
> ComponentTag-s are cached together with the corresponding Markup and then
> reused for later renderings. But the problem is, that those ComponentTag-s
> are mutable (at least in case of tags with wicket:message attribute) and
> their IDs are changed on every rendering and this produces ID conflicts when
> MarkupContainer.renderNext tries to find or create components corresponding
> to the tags.
> Interesting is, that we can reproduce this bug only in DEVELOPMENT mode. In
> DEPLOYMENT mode everything seems to work. The solution would be to make
> ComponentTags immutable and do not allow to change them, but to create copies
> (there is mutable method in ComponentTag, which is used in some cases).
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