protected void initRepository() throws Exception {
    descriptor = new MongoDBRepositoryDescriptor();
    descriptor.name = repositoryName;
    descriptor.server = null; // use defaults
    MongoDBRepositoryService repositoryService =
        Framework.getLocalService(MongoDBRepositoryService.class);
    repositoryService.addContribution(descriptor);

    clearMongoDb();
  }
 protected void closeRepository() {
   Framework.getService(RepositoryService.class).shutdown();
   MongoDBRepositoryService repositoryService =
       Framework.getLocalService(MongoDBRepositoryService.class);
   repositoryService.removeContribution(descriptor);
 }