Nested jar files

Question

two questions:
1) How can I get access to a nested jar file? That is lets say i have a jar file names "Outer.jar", which includes two jar files. These two inner jar files each have a main method. Example: "Inner1.jar" and "Inner2.jar". How can I run each inner jar file? Is this possible?
That is: "Inner1.jar" works perfectly fine by itself, if it was the only jar file, and it has it's own main method. The same goes for "Inner2.jar". But, How can I put these two into a main jar file, "Outer.jar", and then run each of the two inner jar files?
2) Is it possible to make a jar file that contains two jar files both of which have separate main methods?

Answer 1

It makes a great deal of sense to nest jar files. For example, I'm trying to put together a standalone JavaHelp "document". Wouldn't it be great if my customer could double click on a jar file and have a JavaHelp view open up with the documents inside? This requires bundling a JavaHelp jar, a viewer jar, and the document jar containing the docs and helpset. The only thing the customer needs in a JRE. No fuss, no muss, no messy installation.
Another situation is where I want to bundle up multiple jar files as one to simplify distribution and deployment.
--jon
I've never heard of anyone wanting to do this before
but:
1. I think the only way to do this will be to use a
custom classloader. You could have a runnable class in
your Outer.jar that launches a custom classloader.
This custom classloader will load your classes and you
can call your runnable classes in Inner1.jar and
Inner2.jar using seperate threads. You need a custom
classloader because if you launch you .jar from (for
example) "D:\myJar\Outer.jar" and specify the
classpath (in the JAR manifest file) to (for example)
"lib/Inner1.jar" it won't look at the JAR file entry
"lib/Inner1.jar" it will look in
"D:\myJar\lib\Inner1.jar". You're going to have
problems though because you're basically running 3
programs in 1 JVM. Things like static variables and
security are going to be an issue. Basically unless
there is a very good reason to do this, it sounds like
a bad idea.
2. Yes.