Re: Execute main() from a running program

From:

Mark Space <markspace@sbcglobal.net>

Newsgroups:

comp.lang.java.programmer

Date:

Fri, 16 Jan 2009 07:31:51 -0800

Message-ID:

<gkq99e$1sl$1@news.motzarella.org>

robert wrote:

Hi all,

We have a typical servlet container app, and also a separate app that
uses an OSS library that must be invoked with its main() . We are
integrating the main() app into the servlet container app. We execute
the main() app via ant, and I'm executing it in the container via ant
programatically just fine for now. However, that of course starts up
another JVM. Is there a way to invoke a main() program from a running
program, without starting up another JVM?

Probably. The easiest would just be to use the package name, class and
method in your app, like "other.jar.Classname.main( null );" and put the
..jar file where the web app will find it (like WEB-INF/lib).

If that's not practical for some reason, you can open the .jar file and
get its manifest (the Java API has classes for both Jarfiles and
Manifests). Get the main class name out of the manifest, then load that
from the jar file and call the method name reflectively.

You may wish to use classloaders to isolate your app from the library,
but that might be overkill too.