AccountPatchAPI.apxc

@RestResource(urlMapping='/v1/account/*')
global  class AccountPatchAPI {  
    @HttpPatch
    global static Account patch() {
        RestRequest req = RestContext.request;
        // Deserialize the JSON string into name-value pairs
        
        // Iterate through each parameter field and value
        List<APIMapper__c> mappers=[select id,FieldName__c,MappedFieldAPI__c  from APIMapper__c where name='AccountPatch'];
        Map<string,string> mapFields=new Map<string,string>();
        if(mappers!=null && mappers.size()>0)
        {
            for(APIMapper__c mapObject:mappers)
            {
            	mapFields.put(mapObject.FieldName__c,mapObject.MappedFieldAPI__c);
            }
        }
        
        Map<String, Object> params=(Map<String, Object>)JSON.deserializeUntyped(req.requestbody.tostring());
		system.debug('params:' + params);
        string accts =string.valueOf(params.get('accountNumber'));   // get Account number to update record
        
        //Create new map with fields mapped in object
        Map<String, Object> newParams=new  Map<String, Object>();
      	for(String fieldName : params.keySet()) {
            String val = mapFields.get(fieldName);
            if(string.isNotBlank(val))
            {
                newParams.put(val,params.get(fieldName));
            }
        }
        
        //Update Record using mapped value
        system.debug('newParams:' + newParams);
       	List<Account> accounts=Database.query('select Id from account where AccountNumber=:accts');
        if(accounts!=null && accounts.size()>0)
        {
            Account acct=accounts[0];
            for(String fieldName : newParams.keySet()) {
                // Set the field and value on the Case sObject
                acct.put(fieldName, newParams.get(fieldName));
            }
            update acct;  
            return acct;
        }
        
        //update account;
        return null;//account.Id;
    }  
}