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Date: Tue, 06 Sep 2005 19:46:56 -0700
From: Jeremy Boynes <jboynes@apache.org>
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To: Derby Development <derby-dev@db.apache.org>
Subject: Re: Sharing code
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Daniel John Debrunner wrote:
> 
> You or I might not, but I'm assuming the worst case where the end-user
> has no idea about classpath, or maybe even Java. They have just
> installed two applications, one which uses Derby client at version X and
> one which uses Derby embedded at version Y.
> 

I would hope for that kind of environment the installer for each 
application took care of separating the classpaths so the user was never 
exposed to them. After all one could be using embedded X and the other 
embedded Y with all sorts of unexpected consequences.

That, and nasty platform issues like the 256 char length, are why most 
applications have evolved away from using the environment to solutions 
like extension directories.

In many cases, applications /want/ to be able to load different versions 
  concurrently, not just application servers and frameworks like Spring 
or OSGI but also build tools like Ant or Maven and development tools 
like Eclipse. None of these are able to use the traditional classpath alone.

Clarity in which jar is providing which class (once and only once) 
greatly simplifies things. Users can use the capabilities of the 
application (such as classloader hierarchies and ordering) to ensure 
that the correct version is used for each component without risk of 
cross-contamination between functions.

--
Jeremy