[Grok-dev] Re: Custom Exception Views and application_url

Roman Lacko rlacko at gratex.com
Wed Apr 2 04:29:05 EDT 2008

Martijn Faassen <faassen <at> startifact.com> writes:

> Lacko Roman wrote:
> [snip]
> > Please can someone tell me how to properly use custom exception views ?
> I think the main problem is that it's hard to make a custom exception 
> view for IUnauthorized. I think other exception views shouldn't have the 
> problem you faced.
> The problem here is two-fold:
> * I believe the default exception view for IUnauthorized is the one that 
> causes the login-prompt to be shown. You're overriding it, so it never 
> happens.
> * You get your special view outside of an application, so it cannot find 
> the application root.
> Generally I believe that using Zope 3's authentication mechanism is 
> probably preferable to overriding IUnauthorized, but I'm handwaving some 
> details here. I can't think for the moment how one would customize the 
> view you see if your login *failed* without overriding IUnauthorized.
> Skins are indeed a possible way around this. If you make sure your 
> application works in a skin and your IUnauthorized view is in a skin, 
> the you cannot get it when you're not in that skin yet, i.e. the grok 
> installation screen.
> You can make your application be in another skin by default by doing 
> something like this:
> from zope.app.publication.interfaces import IBeforeTraverseEvent
> @grok.subscribe(MyApp, IBeforeTraverseEvent)
> def setSkin(obj, event):
>     zope.publisher.browser.applySkin(event.request, MyLayer)
> where MyLayer is used by the skin you want to apply, something like this 
> (untested):
> class MyLayer(grok.IGrokLayer):
>      pass
> class MySkin(grok.Skin):
>      grok.layer(MyLayer)
> and you make your views be in that layer:
> class MyView(grok.View):
>     grok.layer(MyLayer)
> Regards,
> Martijn

Hi Martijn and others,

I have one more problem with layers and "static" files.

In my main template "master.pt" I have following expression:
<link tal:attributes="href static/styles.css"
rel="stylesheet" type="text/css" href="styles.css" />

when I try browse my application, exception raised:
Traceback (most recent call last):
  <list of files in stack>
    return expression(self)
   - d:\src\klucsiteenv\klucsite\src\klucsite\app_templates\master.pt
   - Line 10, Column 2
   - Expression: <PathExpr standard:u'static/styles.css'>
   - Names:
      {'args': (),
       'context': TraversalError(None, 'styles.css'),
       'default': <object object at 0x00A705C0>,
       'loop': {},
       'nothing': None,
       'options': {},
       'repeat': {},
       'request': <zc.resourcelibrary.publication.Request instance
       'static': None,
       'template': <grok.components.TrustedFilePageTemplate object at 
       'view': <klucsite.app.SystemError object at 0x02EF6EB0>}
line 217, in __call__
    return self._eval(econtext)
line 194, in _eval
    ob = self._subexprs[-1](econtext)
line 124, in _eval
    ob = self._traverser(ob, element, econtext)
line 68, in __call__
line 164, in traversePathElement
    return traversable.traverse(nm, further_path)
   - __traceback_info__: (None, 'styles.css')
line 52, in traverse
    raise TraversalError(subject, name)
   - __traceback_info__: (None, 'styles.css', [])
TraversalError: (None, 'styles.css')

It seems that path expression "static/styles.css" was evaluated to 

Can some one show me how to properly handling static files
when using layers and skins ?

Thank for your help


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