JSON Serialization and Callouts

HttpRequest request = new HttpRequest();
request.setEndpoint('callout:Weather_API/current?city=Cape+Town');
request.setMethod('GET');
request.setHeader('Content-Type', 'application/json');

Http http = new Http();
HttpResponse response = http.send(request);

HttpRequest describes the call (endpoint, method, headers); Http.send() actually performs it and returns an HttpResponse — this is the Apex equivalent of the browser's fetch, used here because only Apex can perform the callout at all (Lesson 1).

// Dynamic/unknown shape — a generic Map
Map<String, Object> data = (Map<String, Object>) JSON.deserializeUntyped(response.getBody());
Decimal temperature = (Decimal) data.get('temperature');

// Known, stable shape — a typed Apex class
public class WeatherResponse {
    public Decimal temperature;
    public String conditions;
}

WeatherResponse weather = (WeatherResponse) JSON.deserialize(response.getBody(), WeatherResponse.class);

JSON.deserializeUntyped produces a generic Map<String, Object> — flexible, but every value needs an explicit cast and there's no compile-time checking of property names. JSON.deserialize into a matching Apex class is preferred whenever the response shape is stable and known in advance — it gives compile-time-checked, typed property access instead.

public with sharing class WeatherService {
    public static WeatherSummary getCurrentWeather(String city) {
        HttpRequest request = new HttpRequest();
        request.setEndpoint('callout:Weather_API/current?city=' + EncodingUtil.urlEncode(city, 'UTF-8'));
        request.setMethod('GET');

        HttpResponse response = new Http().send(request);
        WeatherResponse raw = (WeatherResponse) JSON.deserialize(response.getBody(), WeatherResponse.class);

        return new WeatherSummary(raw.temperature, raw.conditions);
    }
}

The raw API response is deserialized into an internal WeatherResponse class, then mapped into a WeatherSummary wrapper (Module 7's DTO pattern) — exactly the kind of clean boundary that decouples the component from the external API's own response shape.