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List:       tapestry-user
Subject:    Re: Help needed with DirectLink and page parameters (Was: Contrib:Table and page parameters)
From:       "Marcus Schulte" <etluchs () googlemail ! com>
Date:       2007-12-21 21:33:48
Message-ID: 2a68ac4d0712211333k3c3a3774n9be12c4e9b35f67e () mail ! gmail ! com
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2007/12/21, Kaspar Fischer <fischerk@inf.ethz.ch>:
> 
> 
> On 20.12.2007, at 18:16, <Marcus.Schulte@bmw.ch>
> <Marcus.Schulte@bmw.ch> wrote:
> > > Does this mean that Tapestry will keep in its page pool an
> > > IExternalPage page for each article I have in the DB (once
> > > this page is visited)?
> > 
> > Please refer to
> > http://tapestry.apache.org/tapestry4.1/usersguide/state.html
> > Tapestry will keep in its pool one instance for each *concurrent
> > request* it is serving. Your persistent page-id will be stored in the
> > session or on the client (configurable).
> > When a request comes in, Tapestry will pick a page from the pool and
> > provide it with the persistent property data, e.g. the reference to
> > your
> > db-data.
> 
> I don't see how this solves my problem of emitting DirectLinks with
> parameters into the page. If I understand you correctly, you say that
> by using persisted properties, my DirectLinks do not need to contain
> the page's parameters, right?
> 
> Suppose my article page contains a link to download the article. This
> link is implemented via a DirectLink. Suppose now the user opens two
> tabs,
> in this order:
> 
> http://my.org/app?page=Article&id=1
> http://my.org/app?page=Article&id=2
> 
> After this, the session holds "id=2". Now the user clicks the download
> link in the former page (id=1). As this DirectLink does not contain
> "id=1"
> the user will get article 2. That's not what the user expects.
> 
> Do I misunderstand this?
> 
> It seems to me that persistent properties do not solve the problem. I
> need a way to tell DirectLink to look up the current external page's
> parameter's and embed them in the link.


Sounds like what you really want is client-side persistence. This will store
your page-state in the URL - or in a hidden field, if your page uses forms.
So, to be concrete, if you're having a non-null property annotated with
@Persist("client"), or tagged appropriately in the .page xml-File, your
direct Link will, magically, render as something like:

http://localhost:8080/myapp/app?component=dl&page=Home&service=direct&state:Home=BrO0ABXcQAAAAAQAACXRyaWdnZXJlZHQAATE%3D


The funny String making up the value of the parameter "state:Home" is
actually the Base64 encoded version of your page-state. That way, a user
opnening several instances of your page in multiple browser windows/tabs
will see what he expects (possibly ;))

Btw., don't worry about asking basic questions, that's ok, of course.


Marcus

-- 
Marcus Schulte
http://marcus-schulte.blogspot.com



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