When the component jar of a Java extension has an index, openoffice fails to
supply classes that are in a different (non-uno) jar in the extension. 
Say for example I have an extension test.oxt with a component jar comp.uno.jar
and an utils jar utils.jar. When I put an index in comp.uno.jar a
ClassNotFoundError is thrown when classes in comp.uno.jar refer to classes in
utils.jar.
The attached zip file contains a test case that shows this. It installs a
Toolbar with one button, which, when clicked, shows a message box saying 'Jar
index test FAILED!'. The error is logged to %user.home%/ooo-test-jarindex.%u.log
where %u is an int used to make the log file unique.