MavenRepository publicRepo = repositoryRegistry.getRepositoryWithFacet("public", MavenGroupRepository.class);
ResourceStoreRequest req =
new ResourceStoreRequest("/org/apache/maven/apache-maven/3.0-beta-1/apache-maven-3.0-beta-1.pom");
StorageFileItem pomItem = (StorageFileItem) publicRepo.retrieveItem(req);
ModelSource pomSource = new FileItemModelSource(pomItem);
List<MavenRepository> participants =
Arrays.asList(pomItem.getRepositoryItemUid().getRepository().adaptToFacet(MavenRepository.class));