how to parse json to list?

Question

{"rates":{"2019-01-03":{"CAD":1.7043139339,"EUR":1.1072725662,"USD":1.2565329081},"2019-01-04":{"CAD":1.7033382229,"EUR":1.111259279,"USD":1.2671689559},"2019-01-02":{"CAD":1.7242832585,"EUR":1.1090778018,"USD":1.2640159707}},"start_at":"2019-01-01","base":"GBP","end_at":"2019-01-05"}

when I try to convert to a list I get an error

 public class updateExchangeRates {

        public class cls_rate {
            public rates rates;
            public String base;
            public Date date_x;
        }    
        public class rates {
            public Decimal CAD;
            public Decimal EUR;
            public Decimal USD;
        }

        public class exchangeRateList {
            public List<Exchange_Rate__c> cls_rate;
        }

        public void getExchangeRatesList(){
            Http http = new Http();
            HttpRequest request = new HttpRequest();
            request.setEndpoint('https://api.exchangeratesapi.io/history?start_at=2018-01-01&end_at=2018-02-01&symbols=USD,EUR,CAD&base=GBP');
            request.setMethod('GET');
            HttpResponse response = http.send(request);
            // If the request is successful, parse the JSON response.
            //cls_rate rat = new cls_rate();
            if (response.getStatusCode() == 200) {

                List<Exchange_Rate__c> exchangeList = (exchangeRateList) System.JSON.deserialize(response.getBody().replace('"date":', '"date_x":'), exchangeRateList.class);     


            }
        }
    }

That's because the JSON itself is not a list structure... it's a map structure ({} rather than []). If you want to make a list out of this, you will need to do some of your own conversion by deserializing it into a map structure first and then looping through the values of the map. — user72164
– user72164, Commented Sep 17, 2019 at 19:22
Why not use this that will generate APEX bean for you?adminbooster.com/tool/json2apex — Pranay Jaiswal
– Pranay Jaiswal, Commented Sep 17, 2019 at 20:02
I would use this JSON2Apex website to generate a JSON parsing class. And then, I would use a Map to extract the necessary [Key, values] and then easy to extract the necessary values to be my list. Refer this post. — SatyaV
– SatyaV, Commented Sep 17, 2019 at 20:04

Keith C · Accepted Answer · 2019-09-17 21:22:09Z

Worth putting JSON through e.g. https://jsonformatter.curiousconcept.com/ so the structure is clearer:

{ 
   "rates":{ 
      "2019-01-03":{ 
         "CAD":1.7043139339,
         "EUR":1.1072725662,
         "USD":1.2565329081
      },
      "2019-01-04":{ 
         "CAD":1.7033382229,
         "EUR":1.111259279,
         "USD":1.2671689559
      },
      "2019-01-02":{ 
         "CAD":1.7242832585,
         "EUR":1.1090778018,
         "USD":1.2640159707
      }
   },
   "start_at":"2019-01-01",
   "base":"GBP",
   "end_at":"2019-01-05"
}

Given the date strings used as property names (and no arrays are involved as Bryan says and https://json2apex.herokuapp.com/ doesn't AFAIK handle varying property names), probably easiest to walk through the maps in your code:

class Rate {
    String date;
    Decimal cad;
    Decimal eur;
    Decimal usd;
}

Rate[] rates = new Rate[] {};

Map<String, Object> rootMap = (Map<String, Object>) JSON.deserializeUntyped(jsonString);
Map<String, Object> ratesMap = (Map<String, Object>) rootMap.get('rates');
for (String date : ratesMap.keySet() {

    Map<String, Object> rateMap = (Map<String, Object>) ratesMap.get(date);

    Rate rate = new Rate();
    rate.date = date;
    rate.cad = (Decimal) rateMap.get('CAD');
    rate.eur = (Decimal) rateMap.get('EUR');
    rate.usd = (Decimal) rateMap.get('USD');

    rates.add(rate);
}

I learnt something new from this answer., i.e., JSONFormatter. You are the best, Keith! — SatyaV
– SatyaV, Commented Sep 18, 2019 at 14:31

Bryan Anderson · Accepted Answer · 2019-09-17 19:23:10Z

2

The JSON being returned is not in a list

[{...},...]

Therefore you cannot cast it as a list

answered Sep 17, 2019 at 19:23

Bryan Anderson

2,50618 silver badges21 bronze badges

Add a comment |

Stack Exchange Network

how to parse json to list?

2 Answers 2

You must log in to answer this question.

Linked

Hot Network Questions

how to parse json to list?

2 Answers 2

You must log in to answer this question.

Linked

Related

Hot Network Questions