public with sharing class DataTableServerContrl {
    @AuraEnabled
    public static Map<object,object> fetchOpportunities(String limitSize, String offsetSize) {
      Map<object,object> contrlRes = new Map<object,object>{
        'records' => null,
        'fieldApiAndDataTypes' => null,
        'fieldLabels' => null,
        'totalSize'   => null
      };
      system.debug('***limitSize: '+limitSize);
      system.debug('***limitSize: '+offsetSize);
      List<Schema.FieldSetMember> oppFields = LightningUtility.getFieldSetFields('Opportunity','Opportunity_ReadableFields');
      String selFieldsStr = LightningUtility.getFieldApiNames4QueryString(oppFields,'Opportunity');
      system.debug('selFieldsStr: '+selFieldsStr);
      String theQuery = LightningUtility.getQueryString('Opportunity',selFieldsStr,limitSize,offsetSize);
      system.debug('theQuery: '+theQuery);
      //contrlRes.put('fieldApiAndDataTypes', LightningUtility.getFieldApisLstOfFieldSet(oppFields));
      system.debug('***'+LightningUtility.getFieldApisAndDTyesLstOfFieldSet(oppFields,'Opportunity'));
      contrlRes.put('fieldApiAndDataTypes', LightningUtility.getFieldApisAndDTyesLstOfFieldSet(oppFields,'Opportunity'));
      system.debug('@@@'+contrlRes.get('fieldApiAndDataTypes'));
      contrlRes.put('fieldLabels', LightningUtility.getFieldLabelsLstOfFieldSet(oppFields,'Opportunity'));
      contrlRes.put('records', Database.query(theQuery));
      contrlRes.put('totalSize', Database.query(LightningUtility.getQueryString('Opportunity',selFieldsStr,null,null)).size());
      return contrlRes;
    }
    @AuraEnabled
    public static Opportunity fetchOpportunity(String oppId) {
      return [select Name, Amount from Opportunity where id =: oppId];
    }
    @AuraEnabled
    public static String updateOpp(String oppId, Decimal amt) {
      String statusMsg = 'Success';
      try {
        update new Opportunity(Id = oppId, Amount = amt);
      }
      catch(Exception e) {
        statusMsg = 'Error: '+e.getMessage();
      }
      return statusMsg;
    }
}