Loading classes from another jar file

Question

I've set up my jnpl file so that it references a core jar file (contains main() function). The jnlp also references another jar file (app.jar) which contains class files that I load and instantiate dynamically (using ClassLoader). The core.jar file contains a manifest that includes a reference to app.jar.
The app works fine when I use "java -jar core.jar" from the command line.
However, when I wrap the jars using jnlp, I always get a null pointer exception because it cannot find any class that is in the app.jar file. I've tried different strategies, such as trying to load a class file that sits on the server (in a jar file and not in a jar file), but that also fails if I use jnlp (However, it works if I use "java -jar core.jar")
Any ideas what is going on?

Answer 1

This is the "OckCore.jar" manifest before signing:
Manifest-Version: 1.0
Main-Class: com.Ock.OckCore.OckApp
Class-Path: . OckMaths.jar
Created-By: 1.4.0-beta3 (Sun Microsystems Inc.)
Name: com.Ock.OckCore.OckApp.class
Java-Bean: FalseThis is the manifest after signing:
Manifest-Version: 1.0
Main-Class: com.Ock.OckCore.OckApp
Created-By: 1.4.0-beta3 (Sun Microsystems Inc.)
Class-Path: http://hazel/Ock/. http://hazel/Ock/OckMaths.jar
Name: com/Ock/OckCore/OckApp.class
SHA1-Digest: KRZmOryizx9o2L61nN+DbUYCgwo=I have removed a load of irrelevant stuff from the "after" manifest to keep it readable.
note that :-
The OckApp.class loads normally from webstart and tries to load a class from OckMaths.jar.
I can prove that OckApp.class does load because it creates a log file when it does.
The OckApp.class tries to load a class from the OckMaths.jar. This fails if webstart is used but works if OckCore is launched using "java -jar OckCore.jar".
The jars do exist at the location specified by the manifest.
The application launches normally if I use "java -Jar OckCore.jar"
Here is the jnlp file
<?xml version='1.0' encoding='UTF-8'?>
<jnlp
     spec="1.0"
     codebase="http://hazel/Ock"
     href="OckMaths.jnlp">
     <information>
          <title>Ock Maths Demo</title>
          <vendor>Rodentware Inc</vendor>
          <description>Demo of a ported app running as a Java Webstart application</description>
          <description kind="short">An app running as a Java Webstart application"></description>
          <offline-allowed/>
     </information>
     <security>
          <all-permissions/>          
     </security>
     <resources>
          <j2se version="1.3"/>
          <jar href="OckCore.jar"/>
          <jar href="OckMaths.jar"/>
     </resources>
     <application-desc main-class="com.Ock.OckCore.OckApp">
</jnlp> I have also signed the jars outside of a webdirectory. I get the following manifest file:
Manifest-Version: 1.0
Main-Class: com.Ock.OckCore.OckApp
Created-By: 1.4.0-beta3 (Sun Microsystems Inc.)
Class-Path: . OckMaths.jar
Name: com/Ock/OckCore/OckApp.class
SHA1-Digest: KRZmOryizx9o2L61nN+DbUYCgwo=
note that :-
The jars do exist at the location specified by the manifest.
The application launches normally if I use "java -Jar OckCore.jar".
The application doesn't launch from webstart.
I've found that cache, but the jar files have been renamed.
OckCore.jar is anOckCore.jar, etc... so I'm not sure if trying to write a cmdline will work anyway.