@Path("{versionNumber}/operating_systems")
  public OperatingSystemService getOperatingSystemsHandler(@PathParam("versionNumber") String versionNumber) {
    final Map<Resource.Type, String> mapIds = new HashMap<>();
    mapIds.put(Resource.Type.VersionDefinition, versionNumber);
    return new OperatingSystemService(mapIds);
  }
Handles ANY /{versionNumber}/operating_systems requests.

@param versionNumber the repository version id, whether it be from the DB or available.
@return operating systems service
ambari-server/src/main/java/org/apache/ambari/server/api/services/VersionDefinitionService.java