Currently the JarArchive / DefaultJarArchive only provides a read-only access.
It would be nice to have functionality to be able to modify (add/remove/change) the files within a Jar archive, explode the JAR into a directory, etc.
I don't know whether this should be in the interface (JarArchive), or only in the implementation (DefaultJarArchive).
Also, the current implementation stores the Jar (or war, etc) content as a member variable (private byte content). This means that if the archive is large it eats a lot of memory - it could (in findResource) create a JarInputStream from the File that it was passed originally.