But we already have a page reference number already in place
that tracks the current Page referenced by the user. You are right that
we need extra data on the client side to track this (i.e. encode it as
part of the URL), but we don't need a 36 digit unique ID for that. We
just sequentially increment the page number as we're already doing. If
the user goes back and edits some model element that has been removed,
what I think should happen is:1) Server detects the user moved back to a previous page because the client page and server page numbers are not equal 2) Server invokes UndoableEdits until the server and client pages are equal 3) Server handles the user request as usual. 4) Model detects that the user referenced an invalid element and throws an error. This should occur regardless of whether the user hits the Back key and makes this mistakes or tries "hacking" the server by modifying the URL directly. The bottom line is that this isn't (in my view) a "back button issue". It is a normal issue any normal webapp should be designed to handle -- basic validation routines. Gili On Mon, 7 Mar 2005 20:01:21 +0100, Jan Blok wrote: >Hi, > >> the main problem is that i don't understand (and johan >> probably posted >> this but i don't have it)... exactly what problem are we >> trying to solve here? > >Johan was explaining the problems with the browser "back" button, in for >example a workflow application where the user has to process 5 records >which are rendered to him one after another, by replacing the >model(object) in a component on the server. At a certain point he >decides to go back to fill-in something he missed, when he now submits >the page to the server there is a browser-to-model out of sync problem, >which can be solved by attaching an uuid to each model and rendering >this to the browser > >Another problem I can imagion is a user deleting a list item, going back >with back button, submit a change, now he edits unknowingliy the item >after the deleted item, this also can be detected by an uuid > >So im suggesting a "hard" link between a rendered output and server >model object instance..., by means of a uuid which the developer "can" >choose to use in his model implementation. (instead of the current >component name binding only, thus without binding on the component model >object instance) > >Regards Jan Blok > > > >> -----Original Message----- >> From: [EMAIL PROTECTED] >> [mailto:[EMAIL PROTECTED] On Behalf >> Of Jonathan Locke >> Sent: Monday, March 07, 2005 6:52 PM >> To: [email protected] >> Subject: Re: [Wicket-develop] More Model suggestions, was >> "backbutton problem" >> >> >> >> with this wacky email server on sourceforge i have your >> response but not >> johan's original post! >> >> DetachableModel was replaced by AbstractDetachableModel, which is >> designed for anonymous subclassing. >> >> yes, a UUID ought to be a low security risk in most cases and >> would be >> less of a performance problem than other options for client >> side state. >> >> however, i think AbstractDetachableModel is useful in its own >> right and >> that we ought to keep it as-is. >> >> i'm having trouble with your sketch below for several reasons i can't >> quite articulate yet... >> >> the main problem is that i don't understand (and johan >> probably posted >> this but i don't have it)... exactly what problem are we >> trying to solve >> here? >> >> i don't see any real advantage to storing a UUID on the client if you >> still have a Page and a model on the server. you haven't reduced the >> server state to zero. if you want zero server state, that is already >> supported via bookmarkable pages. a bookmarkable page >> constructs itself >> entirely from request information. you can stick your UUID in >> PageParameters and pass that to BookmarkablePageLink and away >> you go. >> when the request comes in your page will be created and you can >> synthesize your page's model and structure based on the abstracted >> request information in PageParameters. i think this is >> actually quite >> elegant and simple in terms of solving the problem of constructing >> zero-state pages. >> >> Jan Blok wrote: >> >> >Hi, >> > >> > >> > >> >>somehow we have to have more state loaded into the client >> >>(but i don't like this, get .NET feelings now...) >> >>so that the right model can first be created again before >> any action >> >>(form population from the request and the action handling) >> >>any other ideas? >> >>johan >> >> >> >> >> > >> > >> > >> >I totally agree with Johan, is it an idea to change >> IDetachableModel to? >> >: >> > >> >public interface IDetachableModel extends IModel >> >{ >> > public String getUUID();//max length 36 chars, limit this to >> >prevent flooding the page like .NET >> > >> > public void attach(String uuid); >> > >> > public void detach(); >> >} >> > >> >Hmm, IDetachableModel is changed to IDetachable? Recently? >> > >> >If you pass the uuid into the pagereponse (forms/links) if the model >> >returns one, it can be used to lookup the correct modelstate at all >> >times. >> > >> >Max length 36 is for a GUID alike thing like: >> >10030100-E260-11CF-AE68-00AA004A34D5 so you can address any >> molecule in >> >the universe :-), instead of a GUID you could use a uuid like >> >"orders_23461567" for specific hibernate "order" object. >> >By keeping the length limited you also prevent HTTP-POST req. as .NET >> >has for any action. >> > >> >Regards Jan Blok >> > >> > >> > >> >------------------------------------------------------- >> >SF email is sponsored by - The IT Product Guide >> >Read honest & candid reviews on hundreds of IT Products from >> real users. >> >Discover which products truly live up to the hype. Start reading now. >> >http://ads.osdn.com/?ad_id=6595&alloc_id=14396&op=click >> >_______________________________________________ >> >Wicket-develop mailing list >> >[email protected] >> >https://lists.sourceforge.net/lists/listinfo/wicket-develop >> > >> > >> > >> >> >> ------------------------------------------------------- >> SF email is sponsored by - The IT Product Guide >> Read honest & candid reviews on hundreds of IT Products from >> real users. >> Discover which products truly live up to the hype. Start reading now. >> http://ads.osdn.com/?ad_id=6595&alloc_id=14396&op=click >> _______________________________________________ >> Wicket-develop mailing list >> [email protected] >> https://lists.sourceforge.net/lists/listinfo/wicket-develop >> > > > >------------------------------------------------------- >SF email is sponsored by - The IT Product Guide >Read honest & candid reviews on hundreds of IT Products from real users. >Discover which products truly live up to the hype. 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