Classpath problem: .jar file can access a file from Class-Path in manifest, but not from -cp command line parameter

Question

I have the file foo.jar in this directory structure:

+--+- /foo_lib
|  |
|  +- Ice.jar ...
|
+-- /swt-linux-gtk -- swt.jar
|
+-- foo.jar

where manifest says, in part:

Class-Path: . foo_lib/Ice.jar swt-linux-gtk/swt.jar foo_lib/o
 rg.eclipse.core.commands_3.5.0.I20090525-2000.jar...

It can be lauched without problem by the command

java -jar foo.jar

So far, so good. The problem is that I want to set the path to swt.jar (but not the others) from the command line (since different platforms need different versions of swt.jar). So I removed swt-linux-gtk/swt.jar from the manifest and run this command:

java -cp swt-linux-gtk/swt.jar -jar foo.jar

Unfortunately, this doesn't work and I get this exception:

Exception in thread "main" java.lang.NoClassDefFoundError: org/eclipse/swt/widgets/Display
    at scsadmin.BootStrapper$.main(BootStrapper.scala:90)
    at scsadmin.BootStrapper.main(BootStrapper.scala)
    at scsadmin.JavaMain.main(JavaMain.java:9)
Caused by: java.lang.ClassNotFoundException: org.eclipse.swt.widgets.Display
    at java.net.URLClassLoader$1.run(URLClassLoader.java:202)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.net.URLClassLoader.findClass(URLClassLoader.java:190)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:307)
    at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:301)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:248)
    ... 3 more

Is -cp ignored when there is a Class-Path section in the manifest? Or am I missing something else?

Answer 1

From the manpage for java -jar:

When you use this option, the JAR file is the source of all user classes, and other user class path settings are ignored.

It also seems that jar is using a custom classloader to be able to load bundled jars.

Answer 2

When you use "java -jar", the -classpath option is ignored.

See http://download.oracle.com/docs/cd/E17476_01/javase/1.4.2/docs/tooldocs/linux/java.html for more details.

"When you use this option, the JAR file is the source of all user classes, and other user class path settings are ignored."

Cheers, Donald.