code: private static Collection<Class> scanEntityClasses(String... persistenceXmlFiles) {
          DDLGenerator.Profile profile = new DDLGenerator.Profile(null);
          profile.addPersistenceFile(persistenceXmlFiles);
          return profile.getEntityClasses();
      }
docs: <p>Extracts all entity classes in the given set of persistence.xml files an returns a collection thereof.</p>
  @param persistenceXmlFiles set of persistence.xml files that you want to scan
  @return extracted entity classes