Java Manifest file's class path and how it determines relative dirs

How does the Class-path in the MANIFEST.MF file determine the relative location?

1) Say I have a JAR with a jar inside lib/somejar.jar and ofc the manifest file is inside META-INF/MANIFEST.MF. How would I set the classpath....? Would it be Class-path: lib/somejar.jar or ../lib/somejar.jar ?

2) Let's say the somejar.jar also has other jars inside of it that the main jar depends on. And of course somejar.jar also has its own MANIFEST.MF file with a correctly set Class-path field. Now lets then say that the original main jar file, during run-time, needs to access one of those JAR files, will it be able to do so as long as somejar.jar is on mai开发者_JAVA百科n.jar's classpath? Or are the relative directories messed up since the main jar is running 'somejar.jar' isn't the root anymore?

minor update: This will all run in a web environment, on an application server.

When doing it "plain vanilla", you can't have a JAR inside a JAR. You need to either put it outside in a known path relative to the main JAR, or extract the JAR's contents in the main JAR.

But since Eclipse 3.5 you can do this with a builtin trick. Check the 2nd Library Handling option when you choose Export > Runnable JAR file.

When choosing Package required libraries into generated JAR, then Eclipse will add a special classloader which will load those JAR's transparently for you before executing the main class. It's doing that with help of JarRsrcLoader.