An install hook is used to do some pre and post work during a package
install. the hooks need to have at least one class that implements this
interface. the class is identified by the normal "Main-Class" manifest
property and needs to be instantiatable. The instantiated hook class is
used for the entire life-cycle of the installation process until the
InstallContext.Phase.END phase.
The hook jars need to be placed in the "META-INF/vault/hooks" directory
and are executed in alphabetical sequence for each installation phase.
A hook can throw a
PackageException to abort the current phase,
but this has currently only an effect in the
InstallContext.Phase.PREPARE and
InstallContext.Phase.INSTALLED
phase. If a hook fails, the current phase is aborted and all hooks
(also the failing one) are called again with the respective "fail" phase.