What about ListenerInvocationNotAllowedException?
It is 'handled' by DefaultExceptionMapper too.
Regards
Sven
On 06/03/2014 09:03 AM, Martin Grigorov wrote:
Looking at DefaultExceptionMapper#internalMap() I see the following
candidates:
- org.apache.wicket.core.request.mapper.StalePageException
- org.apache.wicket.protocol.http.servlet.ResponseIOException
-
org.apache.wicket.request.resource.PackageResource.PackageResourceBlockedException
Possible names of the marker:
- WicketBadState
- WicketInternalException
- WicketFrameworkException
Martin Grigorov
Wicket Training and Consulting
On Tue, Jun 3, 2014 at 6:34 AM, Sven Meier <[email protected]> wrote:
What would be the name of that interface and which classes would implement
it?
Sven
On 06/02/2014 11:27 PM, Martin Grigorov wrote:
On Mon, Jun 2, 2014 at 11:14 PM, Sven Meier <[email protected]> wrote:
Hi,
the problem I see with an exception interface or #canHandleException() is
that both promise something (i.e. this exception will be handled) but you
cannot be sure that this promise will be kept.
What if you have installed an alternative IExceptionMapper which maps
things differently? Or #canHandleException() get's out of sync with the
actual code in #map(Exception)?
How about adding a hook method #onMapped(Exception,IRequestHandler) to
DefaultExceptionMapper. Subclasses could check for
RenderPageRequeatHandlers *after* Wicket's default mapping was
performed. A
subclass could return an override with the previous page and an error
message instead.
I think the application code should not deal with "special" exceptions
like
ResponseIOException (because this means the connection to the browser is
closed) or StalePageException (because this means the previous page is
stale/obsolete for some reason and needs to be re-rendered to be useful
again).
The idea of the special marker interface is to tell the application "you
better leave this problem to be handled by the framework".
By using this marker interface the application code will be future-proof.
My 2 cents
Sven
On 06/02/2014 10:50 PM, Martin Grigorov wrote:
Hi Ernesto,
On Mon, Jun 2, 2014 at 10:42 PM, Ernesto Reinaldo Barreiro <
[email protected]> wrote:
Martin,
Just an idea,
Besides your marker interface maybe IExceptionMapper can be re-factored
as
1-
public interface IExceptionMapper
{
/** return true if it knows how to handle and exception */
boolean canHandle(Exception e);
/**
* @param e
*
* @return {@link IRequestHandler} for given exception
*/
IRequestHandler map(Exception e);
}
2- Allow a list a of IExceptionMapper's. So, that user can register
mappers
before the default one.
3- This list will be iterated and ask canHandle(e) on each mapper to
see
if
it can handle the exception. The default mapper could handle "all"
exceptions not handle by previous IExceptionMappers.
Maybe overkill?
What is the difference with the current way ?
Now we have a list of IRequestCycleListeners and Wicket asks them one by
one until some returns non-null. If all return null then the last resort
is
used - the IExceptionMapper.
On Mon, Jun 2, 2014 at 9:39 PM, Martin Grigorov <[email protected]
wrote:
Hi,
Recently I had the chance to review some customer applications and
I've
noticed a pattern in both applications:
a custom impl of IRequestCycleListener#onException() checks whether
the
given exception is instance of something that the application knows
how
to
deal with and if it is not then a RenderPageRequestHandler is returned
trying to render the last successfully rendered page. I.e. the idea is
to
show something like an error feedback in the last/current page instead
of
redirecting to InternalErrorPage.
The problem in both impls was that internal/special exceptions like
ResponseIOException, PackageResource.PackageResourceBlockedException
and
StalePageException (and maybe ListenerInvocationNotAllowedException,
AuthorizationException) have been managed by the custom code instead
of
letting Wicket to do its business (in DefaultExceptionMapper).
The fix was to add a check for these exceptions and do nothing. But
Wicket
can add more such special exceptions in the future and the application
logic may break...
What do you think about introducing a special marker interface for all
exceptions which represent some erroneous state and be better handled
by
Wicket rather than by custom code ?
This way a new exception type will handled automatically in the
future.
Or maybe you have a better idea ?
Martin Grigorov
Wicket Training and Consulting
--
Regards - Ernesto Reinaldo Barreiro
