public Resource locate(final EClass contentType, final EAttribute feature, final String value, final String persistenceUnitName) {
      // create EclipseLink URI for saving/loading library model in/from database
      final String query = EclipseLinkURIUtil.createContentsEqualQuery(contentType, feature, value);
      final URI uri = EclipseLinkURIUtil.createEclipseLinkURI(persistenceUnitName, query);

      // save library model instance in database
      final ResourceSet resourceSet = new ResourceSetImpl();

      resourceSet.getResourceFactoryRegistry().getProtocolToFactoryMap().put("eclipselink", new EclipseLinkResourceFactoryImpl());
      resourceSet.getLoadOptions().putAll(getTestPersistenceUnitProperties());

      final Resource resource = resourceSet.getResource(uri, true);

      return resource;
   }