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From "ASF subversion and git services (Jira)" <j...@apache.org>
Subject [jira] [Commented] (WICKET-6908) Possible bug / edge case where page is not detached
Date Mon, 26 Jul 2021 20:04:00 GMT

    [ https://issues.apache.org/jira/browse/WICKET-6908?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17387603#comment-17387603
] 

ASF subversion and git services commented on WICKET-6908:
---------------------------------------------------------

Commit 05ab77655fb00d27ade1402b72db1dc6968b3dbe in wicket's branch refs/heads/WICKET-6908-detach-failure
from Sven Meier
[ https://gitbox.apache.org/repos/asf?p=wicket.git;h=05ab776 ]

WICKET-6908 detach all handlers

even if one throws a RuntimeException


> Possible bug / edge case where page is not detached
> ---------------------------------------------------
>
>                 Key: WICKET-6908
>                 URL: https://issues.apache.org/jira/browse/WICKET-6908
>             Project: Wicket
>          Issue Type: Bug
>          Components: wicket-core
>    Affects Versions: 9.3.0, 9.4.0
>            Reporter: Sebastian Gooren
>            Assignee: Sven Meier
>            Priority: Minor
>         Attachments: quickstart.zip
>
>
> Today I spent the better part of my day investigating a bug report regarding a hibernate
LazyInitializationException.
> Since we use detaching models everywhere and (in general) never see such issues anymore,
this one was interesting :-)
>  
> After much debugging I found out what is happening.
>  
> We have a page which has a database model + links for prev/next item (in the database).
> When the users double-clicks on one of the links, the first click is OK, and the second
click throws a StalePageException during request cycle processing.
>  
> So far, normal.
>  
> However, stepping through the wicket code, this is what happens:
>  
> 1) Resolve to ListenerRequestHandler, execute it, throws StalePageException
> 2) exception mapper handles this and we execute a RenderPageRequestHandler, which re-renders
the page
> 3) the request cycle detaches, which delegates in part to RequestHandlerExecutor.detach()
> 4) The handlers to detach are both handlers from step 1 and 2; During the detach of ListenerRequestHandler,
it initializes ListenerLogData, which (in the PageLogData ctor) throws the StalePageException
again!
> 5) The second handler (RenderPageRequestHandler) is not detached, thus all models in
the page are not detached
> 6) The user clicks on a link and boom, the models are all still attached and there we
get the LazyInitializationException
>  
> I think that (a) RequestHandlerExecutor.detach() should ensure all handlers are detached,
and (b) that failing to collect LogData should not stop the detaching of a request handler.
>  
> What do you think?
>  
> I tried to make the simplest possible Quickstart to demonstrate this.
>  
> Weird stuff: on the homepage of the quick start, the page is properly detached when a
stale link is clicked;
> On another (test) page, the page is not properly detached.
>  
> Steps to reproduce:
>  
> Run Quickstart
> Click on “Test” link on homepage
> Observe that the following is logged:
>  
> Model still attached? false
> Page detaching
>  
> Now click on "Click me (stale link)!”
> Now refresh the page (re-render)
>  
> Observe that the following is logged:
>  
> Model still attached? true
> Page detaching
>  
> —> So the page was not detached
>  
> These steps don’t have the same result on the homepage. So my guess is there is some
relation to the fact that we are interacting with a stateful, non-mounted page.



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