[jira] [Resolved] (WICKET-5810) Component#setVersioned(false) should force singleton component instance per session

["Martin Grigorov (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/WICKET-5810?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Martin Grigorov resolved WICKET-5810.
-------------------------------------
    Resolution: Not a Problem

Page#setVersioned(false) is an *instance* method saying that this page instance won't have several versions.
If you click on a link that creates a new instance of this page class then the new instance has nothing to do with the previous one.
This is the design.
Other frameworks (Tapestry 5.0/5.1) have tried to do what you suggest but they faced problems with this approach.

At https://github.com/martin-g/single-page-instance you may find an attempt to do something similar - one instance per page type per session, ignoring #setVersioned(). Read http://markmail.org/message/ofyvgybcjp5cvf75 for the discussion about it and the problems found with it so far.

> Component#setVersioned(false) should force singleton component instance per session
> -----------------------------------------------------------------------------------
>
>                 Key: WICKET-5810
>                 URL: https://issues.apache.org/jira/browse/WICKET-5810
>             Project: Wicket
>          Issue Type: Improvement
>          Components: wicket
>    Affects Versions: 6.16.0
>         Environment: N/A
>            Reporter: bernard
>         Attachments: NullVersionedPanelReplacement.zip
>
>
> This is a follow-up issue from issue WICKET-5693.
> I am for now dropping from my requirement the provision of a mapper that does not show the version number in the URL, for the reason that this seems to complicate the discussion, not for the reason that I don't need it.
> Instead I am focusing on the essential requirement to prevent double submits which should never happen if a stateful page was truly non-versioned in the session scope, and the latest page instance cannot process a submit request. We can discuss the URL issue later.
> To keep my use case simple, I am creating a basic implementation of a page where the user replaces an old panel with a new one. Once this panel is replaced, the user should not be given the chance to access any page version containing the old panel.
> Only then, IMHO, would the contract of Component#setVersioned(false) be fully implemented.
> When executing the attached test case as a web app, one finds that after panel replacement with the new panel, it is possible to display the page having the version containing the old panel by clicking on the original link to the page.
> It appears that Wicket just starts fresh and forgets that the current version of the page contains the new panel not the old one. It creates new version numbers - however I am not saying that the numbers reflect the number of versions in the session. I understand that most likely only a single version exists.
> I was surprised to find in the "Apache Wicket Cookbook" http://www.packtpub.com/apache-wicket-cookbook/book
> in recipe0203 a complex method to prevent double submits via the old J2EE server token pattern. I was thinking that Wicket, supporting server side component state, actually provides the token via a non-versioned page instance (singleton per session) out of the box. I hope that it is not be too late to implement this essential feature by addressing this Jira issue.
> I acknowledge that panel replacement may have its own issues, but it is useful in a testcase, demonstrating component state. One could simply add a server token to the page instance and process any request depending on it.



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