STM InvocationHandler swallows application exceptions

The STM implementation intercepts calls on transactional objects (ones that implement interfaces marked with the @Transactional annotation). If the application object throws a business exception it is wrapped in an java.lang.reflect.InvocationTargetException and this is raised. Application code is written to anticipate business exceptions but not java.lang.reflect.InvocationTargetException.

The fix is throw the wrapped business exception instead.