public Map<String, ? extends Collection<String>> getServiceComponentFilter() {
      String serializedValue = getCommandParameterValue(SERVICE_COMPONENT_FILTER);

      if (serializedValue != null) {
        Type type = new TypeToken<Map<String, ? extends Collection<String>>>() {
        }.getType();
        return StageUtils.getGson().fromJson(serializedValue, type);
      } else {
        return null;
      }
    }
Retrieve the current set of properties for the requested config type for the relevant cluster.

@return a Map of property names to property values for the requested config type; or null if no data is found
@throws AmbariException if an error occurs retrieving the relevant cluster details
ambari-server/src/main/java/org/apache/ambari/server/serveraction/kerberos/KerberosServerAction.java