Re: Dealing with incompatible dependencies?

From:

"Mike Schilling" <mscottschilling@hotmail.com>

Newsgroups:

comp.lang.java.programmer

Date:

Sat, 19 Sep 2009 16:35:34 -0700

Message-ID:

<h93ps7$78l$1@news.eternal-september.org>

Stefan Weiss wrote:

Hi.

I'm having trouble using two jar'ed resources with different code in
the same namespace. One of the jars is the YUI Compressor [0], which
can compress JavaScript source code. It does that by using the
parser
from the Mozilla Rhino project [1], which it loads from
rhino-1.6R7.jar in the org.mozilla.javascript.* namespace. My
application also depends on Rhino for a different task (running JS
scripts from Java).

So far so good. The problem is that, in order to accomodate
non-standard JavaScript features (like IE's conditional comments),
the YUI Compressor uses patched versions of four Rhino classes, and
won't work with the unpatched originals. Unfortunately, these
changes
interfere with Rhino's ability to run JS.

Depending on which jar I include first, I can either get the
compressor part to work, or the JS interpreter, but not both.

Now I'm left with two different versions of four classes
(Decompiler,
Parser, Token, and TokenStream), all in the org.mozilla.javascript
namespace. Is there a way I can resolve this problem, apart from
rebuilding YUI Compressor and its version of Rhino into a different
namespace (like org.mozilla.yuicjavascript)?

To make matters worse, my application invokes both the JS
interpreter
and the JS compressor from the same method (but I could refactor
that
if necessary).

Use different classloaders to load the two subsystems (compressor and
interpreter.) You can get fancy and load the compatible subsets of
the two from a classloader that's a child of both the other two, but
that's an optimization, and might not be worth the effort, complexity,
and fragility that would result.