code: public void initIdGenerator() {
      if (idGenerator == null) {
        CommandExecutor idGeneratorCommandExecutor = null;
        if (idGeneratorDataSource != null) {
          ProcessEngineConfigurationImpl processEngineConfiguration = new StandaloneProcessEngineConfiguration();
          processEngineConfiguration.setDataSource(idGeneratorDataSource);
          processEngineConfiguration.setDatabaseSchemaUpdate(DB_SCHEMA_UPDATE_FALSE);
          processEngineConfiguration.init();
          idGeneratorCommandExecutor = processEngineConfiguration.getCommandExecutor();
        } else if (idGeneratorDataSourceJndiName != null) {
          ProcessEngineConfigurationImpl processEngineConfiguration = new StandaloneProcessEngineConfiguration();
          processEngineConfiguration.setDataSourceJndiName(idGeneratorDataSourceJndiName);
          processEngineConfiguration.setDatabaseSchemaUpdate(DB_SCHEMA_UPDATE_FALSE);
          processEngineConfiguration.init();
          idGeneratorCommandExecutor = processEngineConfiguration.getCommandExecutor();
        } else {
          idGeneratorCommandExecutor = getCommandExecutor();
        }
  
        DbIdGenerator dbIdGenerator = new DbIdGenerator();
        dbIdGenerator.setIdBlockSize(idBlockSize);
        dbIdGenerator.setCommandExecutor(idGeneratorCommandExecutor);
        dbIdGenerator.setCommandConfig(getDefaultCommandConfig().transactionRequiresNew());
        idGenerator = dbIdGenerator;
      }
    }
docs: /////////////////////////////////////////////////////////////