How to parse a JSON response for APEX REST Service - json

Question

I have written a REST class that sets a url as an endpoint to call an API. The API returns a timezone value. The url passes longitude and latitude as a parameter. The response I am getting is a complicated JSON list and I just need the Id value of the Timezone object. This is what I get as a JSON response for a lat/long value I passed:
{
"Version":"2019c",
"ReferenceUtcTimestamp":"2019-12-10T21:14:23.7869064Z",
"TimeZones":[
{
"Id":"America/Los_Angeles",
"Aliases":[
"US/Pacific",
"US/Pacific-New"
],
"Countries":[
{
"Name":"United States",
"Code":"US"
}
],
"Names":{
"ISO6391LanguageCode":"No supported language code supplied",
"Generic":"",
"Standard":"",
"Daylight":""
},
"ReferenceTime":{
"Tag":"PST",
"StandardOffset":"-08:00:00",
"DaylightSavings":"00:00:00",
"WallTime":"2019-12-10T13:14:23.7869064-08:00",
"PosixTzValidYear":2019,
"PosixTz":"PST+8PDT,M3.2.0,M11.1.0",
"Sunrise":"2019-12-10T07:42:22.383-08:00",
"Sunset":"2019-12-10T16:18:49.095-08:00"
},
"RepresentativePoint":{
"Latitude":34.05222222222222,
"Longitude":-118.24277777777777
},
"TimeTransitions":[
{
"Tag":"PST",
"StandardOffset":"-08:00:00",
"DaylightSavings":"00:00:00",
"UtcStart":"2019-11-03T09:00:00Z",
"UtcEnd":"2020-03-08T10:00:00Z"
},
{
"Tag":"PDT",
"StandardOffset":"-08:00:00",
"DaylightSavings":"01:00:00",
"UtcStart":"2020-03-08T10:00:00Z",
"UtcEnd":"2020-11-01T09:00:00Z"
},
{
"Tag":"PST",
"StandardOffset":"-08:00:00",
"DaylightSavings":"00:00:00",
"UtcStart":"2020-11-01T09:00:00Z",
"UtcEnd":"2021-03-14T10:00:00Z"
}
]
}
]
}
Here is my REST Service in APEX:
public class LPP_AccountTimeZone {
public static List<String> getTimeZone(String latitude, String longitude){
Http http = new Http();
HttpRequest req=new HttpRequest();
String url = 'https://atlas.microsoft.com/timezone/byCoordinates/json?subscription-key=XXXXXXXXXXXXXXXXXXXXXXXXXXXX&api-version=1.0&options=all&query='+latitude+','+longitude;
req.SetEndPoint(url);
req.setMethod('GET');
HttpResponse res=http.send(req);
if (res.getStatusCode() == 200) {
List<String> TimeZone = new List<String>();
TimeZoneJSON result = TimeZoneJSON.parse(res.getBody());
for(TimeZoneJSON.TimeZones t : result.timeZones){
System.debug('TimeZone is' + t.Id);
TimeZone.add(t.Id);
}
}
else{
System.debug('The status code returned was not expected: ' + res.getStatusCode() + ' ' + res.getStatus());
}
return TimeZone[0];
}
The response I got with this code (when I ran it in anonymous window) was:
TimeZone is{Aliases=(US/Pacific, US/Pacific-New), Countries=({Code=US, Name=United States}), Id=America/Los_Angeles, Names={Daylight=Pacific Daylight Time, Generic=Pacific Time, ISO6391LanguageCode=en, Standard=Pacific Standard Time}, ReferenceTime={DaylightSavings=00:00:00, PosixTz=PST+8PDT,M3.2.0,M11.1.0, PosixTzValidYear=2019, StandardOffset=-08:00:00, Sunrise=2019-12-12T07:44:13.44-08:00, Sunset=2019-12-12T16:18:47.934-08:00, Tag=PST, WallTime=2019-12-12T11:49:25.0802593-08:00}, Representativ
That is a lot of info. I just want the America/Los_Angeles part which is what Id equals (I have that bold in the response).
Another problem with this code is that it is not returning anything/is void class.
I need t return that value because a trigger is calling that method and will use this value to update a field.
Can anyone please correct my code so that it passes the correct json value and returns the value?
EDIT/UPDATE: The error I am now getting is "Variale does not exist: TimeZone (where the return statement is)

Answer 1

You could use JSON2APEX to easily generate an apex class from your JSON response. Just paste your full response in and click 'Create Apex'. This creates a class that represents your response so that you can easily retrieve fields from it (Keep in mind this will only really work if your response is static meaning the structure and naming stay the same). Have a look through the class that it generates and that will give you an idea of what to do. The class has a parse(String JSON) method which you can call passing in your JSON response to retrieve an instance of that class with your response values. Then it's just a matter of retrieving the fields you want as you would with any object.
Here is how getting the timezone id code would look if you take this route.
(Note: This assumes you keep the name of the class the standard 'JSON2Apex')
if (res.getStatusCode() == 200) {
JSON2Apex result = JSON2Apex.parse(res.getBody());
for(JSON2Apex.TimeZones t: result.timeZones){
System.debug('TimeZone is' + t.id);
tId.add(t);
}
}
To return a value just change void in the method signature to List<String> and return the tId list as follows return tId;