private Map<String, List<String>> getPayload(Map<String, String> commandParams) throws IOException {
    Map<String, List<String>> payload = objectMapper.readValue(commandParams.get(UserHookParams.PAYLOAD.param()), Map.class);
    return payload;
  }
Validates command parameters, throws exception in case required parameters are missing
ambari-server/src/main/java/org/apache/ambari/server/serveraction/users/PostUserCreationHookServerAction.java