public static KerberosCommandParameterProcessor getInstance(String command, Clusters clusters, ExecutionCommand executionCommand, KerberosKeytabController kerberosKeytabController) {
      if (SET_KEYTAB.equalsIgnoreCase(command)) {
        return new SetKeytabCommandParameterProcessor(clusters, executionCommand, kerberosKeytabController);
      }
      if (CHECK_KEYTABS.equalsIgnoreCase(command)) {
        return new CheckKeytabsCommandParameterProcessor(clusters, executionCommand, kerberosKeytabController);
      }

      if (REMOVE_KEYTAB.equalsIgnoreCase(command)) {
        return new RemoveKeytabCommandParameterProcessor(clusters, executionCommand, kerberosKeytabController);
      }

      return null;
    }
Factory method to return the appropriate KerberosCommandParameterProcessor instance based
on the command being executed.

@param command the command being executed
@param clusters the clusters helper class
@param executionCommand the execution command structure
@param kerberosKeytabController the keytab controller helper class
@return
ambari-server/src/main/java/org/apache/ambari/server/events/publishers/AgentCommandsPublisher.java