getResource (was RE: URL.setURLStreamHandlerFactory - Tomcat 5.0)

[Peter Crowther <Pe...@melandra.com>]

> From: Shapira, Yoav [mailto:Yoav.Shapira@mpi.com] 

Yoav, I have *no* idea what this list would do without you...

> We discussed
> this back as jar as June: see the thread and accompanying 
> Bugzilla issue
> at http://issues.apache.org/bugzilla/show_bug.cgi?id=29631.  
> We decided
> not to allow customization of this for 5.0.x, as too much would be
> involved.

Saw it - hence my response on this list.

> However, before even opening such a discussion, we should consider
> alternatives for your use-case.

Absolutely!

> >- I want to read X.xml from code within the JSP.  What are the ways,
> >accoring to the JSP and servlet specs, that I can do this?
> 
> Numerous ways, with two good ones coming to mind and two bad ones.
> 
> Good:
> URL xUrl = getServletContext().getResource("/path/to/x.xml");

OK.

> URL xUrl = getClass().getResource("/path/to/x.xml/on/classpath");

OK.  That's an interesting case, may need to hack with the classloader.

> Bad:
> URL xUrl = new File("/path/to/x.xml").toURI().toURL();

I'm willing to allow this to fail.  To be honest, I can't see how it
works sensibly anyway...

> URL xUrl = getServletContext().getRealPath("/path/to/x.xml");

Heh.  I know a few that do this... it'd be nice to allow this, possibly
by replacing the implementation of getRealPath(), but I'm also willing
to let it fail.

> You would then parse from a URL using the JAXP APIs, that's fairly
> standard.  Or maybe another higher-level tool like JDOM if that's your
> cup of tea.

Yes.  So, by this time, I need to have remapped the resource so that
opening a stream on the URL gives the 'right' result.

> But note in all these ways the scheme of the URL doesn't 
> matter, it's up
> to the server to resolve them.  The two Good ones above would 
> be jndi:/ URLs.

Indeed.  Which is why I have this nasty suspicion I need to get hold of
the stream handler factory - although potentially it sounds like I could
get away with wrapping the jndi: implementation and intercepting
getRealPath().

> If the container can't resolve it using getResource, that means your
> webapp is not compliant to the Servlet Spec.

Well, that's a nice simple statement to work to :-).  Thanks!  We're
willing to force servlets to be compliant - and to hack Catalina if
necessary, although we'd prefer not to.

> Your resource resolution would be relative to either
> your docBase or your classpath, neither of which are affected by where
> your JSP is.

Cool.

Thanks very much for your help - I'll take a look at this and see what I
can do.  If anyone can think of a funnel in Catalina (or elsewhere)
through which all the legitimate requests pass, I'd appreciate knowing
about it as I may be able to intercept there.

		- Peter

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