Example of a metadata fetcher, a class used to fetch metadata from an
external source in case it's not included in the documents.
This class fetches the metadata from a ZIP file with a certain structure
(specific to the OpenSonar project), but it should be easy to adapt to your
Note that for accessing large ZIP files, you need Java 7 which supports the
ZIP64 format, otherwise you'll get the "invalid CEN header (bad signature)"