On Sat, 9 Jun 2001 [EMAIL PROTECTED] wrote:
> Hi,
>
> I would like to catch all of our project specific exceptions in one place (as a
> last resort, if nobody else catches them earlier on) and handle them in a
> generic way. The obvious way to do this, I think, is by overriding
> processActionPerform in our own <Project>ActionServlet and catch
> <Project>Exception's (superclass for all our own exceptions) there. But the
> Action.perform method only throws IOException & ServletException, so either all
> our own exceptions will have to inherit from either of those two classes (can't
> be the right thing to do), or I will have to change the Action.perform
> definition to also throw our <Project>Exception's (doesn't seem right either,
> I'd prefer not to have to alter any struts code)?
>
> What should I do?
>
How about having the base class for you project exceptions be a subclass
of ServletException? That way, you can throw it if you really want
to. Then you could declare an <error-page> element in your web.xml file
to define common handling (if you don't the default will be an ugly stack
trace on most containers).
> This actually brings me to another problem that doesn't have anything to do
> with struts, but is more a general Java question. Anyway, maybe somebody here
> has an elegant solution to it:
>
> Assume the problem above is solved and furthermore that some of the project
> specific exceptions have to inherit from other existing exception classes (e.g.
> ServletException, IOException, etc.). Since we don't have multiple inheritance,
> I can't have a <Project>Exception that is a superclass to all my own
> exceptions. I still want to catch all our own exceptions (but no others) in one
> place. My first though was of course to define a <Project>Exception interface
> and let all our own exceptions implement this interface, thus being able only
> to catch <Project>Exception's. But Throwable is not an interface (why not?
> What's the idea behind this design?) that <Project>Exception could inherit from
> and thus this approach doesn't work, as the try{}catch(){} statement expects a
> Throwable object as parameter (try{}catch(<Project>Exception e){} doesn't
> compile).
>
> Well, as a kind of a hack I then thought I'll catch all exceptions, check if it
> is a project specific one (<Project>Exception.class.isInstance(anException)),
> and if not throw it again, but that can't be right, because the method where
> this happens then will have to be declared to throw Exception (to generic).
>
> I'll appreciate any help, thanks in advance and the best satisfactory answer
> wins a free beer in Zurich ;-)
>
I'd investigate extending ServletException for your application exception
classes.
Another off-the-wall idea would be to extend RuntimeException instead --
you can throw such an exception without it being listed in the
"throws" clause. This is how things like IllegalArgumentException and
NullPointerException work.
>
> Klaus Bucka-Lassen
>
>
Craig
