Read CSV file and upload data to the system without Saving the CSV

Lead_csvReader.csv

UploadExcel.vfp

<!-- Upload a file and put it in your personal documents folder-->

<!-- Page: -->
<apex:page standardController="Document" extensions="UploadExcelController" showHeader="false">
    <apex:messages />
    <apex:form id="theForm">
      <apex:pageBlock >
          <apex:pageBlockSection >
            <apex:inputFile value="{!document.body}" filename="{!document.name}"/>
            <apex:commandButton value="Save" action="{!save}"/>
          </apex:pageBlockSection>
       </apex:pageBlock>
    </apex:form>
</apex:page>

UploadExcelController.apxc

public class UploadExcelController {
    Document d{get;set;} 
    public UploadExcelController(ApexPages.StandardController controller) {
        d = (Document) controller.getRecord();
        d.folderid = UserInfo.getUserId(); //this puts it in My Personal Documents
    }                 
    
    
    public void save(){
        
        Lead lobj;
        List<Lead> lLead = new List<lead>();
        System.debug('Doc :' + d);
        if(d.body != NULL)
        {
            String sCSV =  EncodingUtil.base64Decode(EncodingUtil.base64Encode(d.body) ).toString();
            System.debug('Body of Doc : ' + sCSV);
            List<String> lstFieldNames = new List<String>();
            List<String> dataLines = sCSV.split('\\n');
            Map <String, Integer> fieldNumberMap = new Map < String, Integer > ();
            
            string[] csvFieldNames = dataLines[0].split(',');
            for (Integer i = 0; i < csvFieldNames.size(); i++) {
                fieldNumberMap.put(csvFieldNames[i], i);
                lstFieldNames.add(csvFieldNames[i].trim());
            }
            
            system.debug('dataLines ' +dataLines);
            
            for (Integer i = 1; i < dataLines.size(); i++) {
                lobj = new Lead();
                string[] csvRecordData = dataLines[i].split(',');
                for (String fieldName: csvFieldNames) {
                    Integer fieldNumber = fieldNumberMap.get(fieldName);
                    String fieldValue = csvRecordData[fieldNumber];
                    lobj.put(fieldName.trim(), fieldValue.trim());
                }
                lLead.add(lobj);                
            }
        }
        
        System.debug('Before insert ');
        if(lLead.size() > 0 ){
            insert lLead;
            ApexPages.Message myMsg = new ApexPages.Message(ApexPages.Severity.FATAL, 'Added successfully!');
            ApexPages.addMessage(myMsg);
            
        }
        System.debug('After insert');
        
    }
}