Apex callout example:

Http http = new Http(); HttpRequest request = new HttpRequest(); request.setEndpoint('https://example.com'); request.setMethod('GET'); HttpResponse response = http.send(request); // If the request is successful, parse the JSON response. if (response.getStatusCode() == 200) { // Deserialize the JSON string into collections of primitive data types. Map<String, Object> results = (Map<String, Object>) JSON.deserializeUntyped(response.getBody()); // Cast the values in the 'animals' key as a list List<Object> animals = (List<Object>) results.get('animals'); System.debug('Received the following animals:'); for (Object animal: animals) { System.debug(animal); } }

Passing Parameters to REST callout:

Http http = new Http(); HttpRequest request = new HttpRequest(); request.setEndpoint('https://th-apex-http-callout.herokuapp.com/animals'); request.setMethod('POST'); request.setHeader('Content-Type', 'application/json;charset=UTF-8'); // Set the body as a JSON object request.setBody('{"name":"mighty moose"}'); HttpResponse response = http.send(request); // Parse the JSON response if (response.getStatusCode() != 201) { System.debug('The status code returned was not expected: ' + response.getStatusCode() + ' ' + response.getStatus()); } else { System.debug(response.getBody()); }

For Test class:

// Create the mock response based on a static resource StaticResourceCalloutMock mock = new StaticResourceCalloutMock();

// Associate the callout with a mock response Test.setMock(HttpCalloutMock.class, mock);

A callout example from trailhead:

@isTest global class AnimalsHttpCalloutMock implements HttpCalloutMock { // Implement this interface method global HTTPResponse respond(HTTPRequest request) { // Create a fake response HttpResponse response = new HttpResponse(); response.setHeader('Content-Type', 'application/json'); response.setBody('{"animals": ["majestic badger", "fluffy bunny", "scary bear", "chicken", "mighty moose"]}'); response.setStatusCode(200); return response; } }

Basic Authentication code:

String username = 'myname';

String password = 'mypwd';  

Blob headerValue = Blob.valueOf(username + ':' + password);

String authorizationHeader = 'BASIC ' +

EncodingUtil.base64Encode(headerValue);

request.setHeader('Authorization', authorizationHeader);

Authentication using Named credentials:

request.setEndpoint('callout:<Nameed credential>/services/data/v32.0');

ref:

https://trailhead.salesforce.com/en/content/learn/modules/apex_integration_services/apex_integration_rest_callouts