Re: Introspect whether setCharacterEncoding is present..

luca <[email protected]> writes:

> Charles Forsythe wrote:
> 
>  >  You could set a
> > Context Attribute (or other flag) based on the following test:
> > 
> >         try {
> >             Class.forName("javax.servlet.http.HttpServletRequestWrapper");
> >             // This is Servlet API >= 2.3 --> Set Attribute/Flag TRUE
> >         } catch(ClassNotFoundException cnfx) {
> >             // This is Servlet API < 2.3 --> Set Attribute/Flag FALSE
> >         }
> 
> I am no expert in this field, but I've always heard that Exceptions
> are for exceptions and not for flow of control (not only is it
> a problem of style, but also performance, I hear)

Where did you hear that?

Exceptions are actually a restricted form of a more general control
structure called a continuation. Continuations can be thrown up the
stack but also down the stack. They do the latter by stack capture.

Anyway, I don't see anything wrong with using exceptions for control
features. Exceptions are, after all, only a long jump, a non local
exit.

Exceptions are NOT just for errors they are a real language feature in
Java, not an afterthought. The fact that exceptions capture the stack
in the form of a trace is also fantastically useful.


In Charles' specific example the catch is being used to handle a
an exception in exactly the right way, it's an exception based
assertion mechanism.


I'm very surprised anyone thinks this is bad style. It isn't.


-- 
Nic Ferrier
http://www.tapsellferrier.co.uk


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