Syncing for Outbound transfer to Salesforce

APISync.apxc.java

@RestResource(urlMapping='/Teams/*')
global with sharing class MyRestResource {

    @HttpPut
    global static String putCustomer(){
        RestRequest req = Restcontext.request;
        List<SObject> sbjectList = new List<SObject>();
        // Deserialize 
        Map<String, Object> params = (Map<String, Object>)JSON.deserializeUntyped(req.requestBody.tostring());
        System.debug(params);
        for(String tableName : params.keySet()){
            
            if (tableName == 'f_user'){
                // find sync Obj
                List<Mapping__mdt> objList = [SELECT Id, SObject__c, Field__c, Column__c
                                    FROM Mapping__mdt 
                                    WHERE Table__c =: tableName];
                if (objList.size()==0) return 'list =0';
                Mapping__mdt obj = objList[0];
                if (obj == null) return 'null';
                if (obj.SObject__c.length()<=0) return 'obj null';
                // get Object by Object name
				Schema.SObjectType objType = Schema.getGlobalDescribe().get(obj.SObject__c);    
                SObject newObj = objType.newSObject();
                
                // put value to sfield
                if (params.get(tableName) instanceof Map<String, Object> ){
                    Map<String, Object> columns = (Map<String, Object>)params.get(tableName);
                    for(String column : columns.keySet()){
                        String sfield = searchSfield(objList, column);
                        System.debug(sfield);
                        if (sfield =='') continue;
                        newObj.put(sfield, columns.get(column));

                    } 
                }
                upsert newObj;
                //sbjectList.add(newObj); 
                System.debug(newObj);
            }
            //thisTeam.put(field, params.get(field));
        }
        
        // insert or update
        //List<SObject> has = [SELECT id FROM :];
        //upsert sbjectList;
        return '200';
    }
    
    // find field name for mapping sync
    private static String searchSfield(List<Mapping__mdt> objList, String column ){
        for(Mapping__mdt record: objList){
            if(column == record.Column__c ){
                String obj_field = record.Field__c;
                // get field
                return obj_field.substring(obj_field.lastIndexOf('.')+1);
            } 
        }
        return '';
    }
    
}