Java Archive files (.jar)

Question

Situation: How do we get around having the same class in multiple jar files? Currently I have two projects sharing the same class. We are attempting to move the class in question to another archive file, but the problem we run into at deploy time is ClassNotFoundException. The only way we got around this problem is to deploy the classes into its on directory and deploy the EJB afterwards. Is there any other solution other than our alternative?
Thank you,
Chris

Answer 1

There's two ways:
1) put it in the parent ClassLoader (e.g. the JVM).
Downside, you make a change, you have to completely
recycle the server (which means an "outage" for
however long that takes). You can also have a class in
that common.jar that does some very
unpredictable things that might compromise the JVM
and/or ClassLoader (such as a "memory leak") which can
compromise the server's operation. Of course, this can
happen in a child ClassLoader, but it usually won't
take the whole thing down with it.
2) You build and "distribute" the common.jar
(as a binary) across your deployable units (EAR, WAR).
This is pretty much the same concept of providing an
EJB-client JAR file for accessing EJBs from a
different JVM or ClassLoader.
As far as I know, these are the only two ways of doing
it - unless you write your own custom ClassLoader
class. Then, of course, you're messing around in the
vendor's ClassLoader area and, if it's proprietary,
you really have no idea what they're actually doing in
there and it could really bite you hard (see #1) if
you make even the smallest mistake.Thanks for the answer. It seems like its just a matter of coordinating independent development teams. We need to come up with some standards, more of a project management thing, yuk.