How to add a class to an existing JAR file.

Say we have a jar file start.jar and want to add a class to it.

$ mkdir jarbuild

$ cp start.jar  jarbuild

$ cd jarbuild

$ jar -xf start.jar

$ rm start.jar

$ cp -r ~/secmgr .

$ find secmgr/

secmgr/

secmgr/manager

secmgr/manager/ProfilingSecurityManager.class

$ jar cmf META-INF/MANIFEST.MF mystart.jar *

Now you have a new jarfile that's the same as start.jar but with the ProfilingSecurityManager class in it. If you want, you can:

$ mv mystart.jar ../start.jar