Designing the client for World Bank API

We need to fetch the GDP data from WorldBank API. As we discussed, it is REST end point, where we have to send few parameters and will get the response. For this, we will use RestTemplate to make REST call. The following is the definition for the com.packt.external.WorldBankApiClient class, which is used to invoke the World Bank API and process its response to return List<CountryGDP>:

@Service
public class WorldBankApiClient {

  String GDP_URL = "http://api.worldbank.org/countries/%s/indicators/NY.GDP.MKTP.CD?"
      + "format=json&date=2008:2018";
  
  public List<CountryGDP> getGDP(String countryCode) throws ParseException {
    RestTemplate worldBankRestTmplt = new RestTemplate();
    ResponseEntity<String> response
      = worldBankRestTmplt.getForEntity(String.format(GDP_URL, countryCode), String.class);
    
    //the second element is the actual data and its an array of object
    JSONParser parser = new JSONParser();
    JSONArray responseData = (JSONArray) parser.parse(response.getBody()); 
    JSONArray countryDataArr = (JSONArray) responseData.get(1);
    
    List<CountryGDP> data = new ArrayList<CountryGDP>();
    JSONObject countryDataYearWise=null;
    for (int index=0; index < countryDataArr.size(); index++) {
      countryDataYearWise = (JSONObject) countryDataArr.get(index);
      
      String valueStr = "0";
      if(countryDataYearWise.get("value") !=null) {
        valueStr = countryDataYearWise.get("value").toString();
      }
      String yearStr = countryDataYearWise.get("date").toString();
      CountryGDP gdp = new CountryGDP();
      gdp.setValue(valueStr != null ? Double.valueOf(valueStr) : null);
      gdp.setYear(Short.valueOf(yearStr));
      data.add(gdp);
    }
    return data;
  }
}