This example sends a GET request to a web service to get a list of woodland creatures. The service sends the response in JSON format. JSON is essentially a string, so the built-in JSONParser class converts it to an object. We can then use that object to write the name of each animal to the debug log.
Http http = new Http();
HttpRequest request = new HttpRequest();
request.setEndpoint('<https://th-apex-http-callout.herokuapp.com/animals>');
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);
}
}
If the request was processed successfully, the status code returns 201, because a resource has been created. The response is sent to the debug log when anything other than 201 is returned.
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());
}
There’s good news and bad news regarding callout testing. The bad news is that Apex test methods don’t support callouts, and tests that perform callouts fail. The good news is that the testing runtime allows you to “mock” the callout. Mock callouts allow you to specify the response to return in the test instead of actually calling the web service. You are essentially telling the runtime, “I know what this web service will return, so instead of calling it during testing, just return this data.” Using mock callouts in your tests helps ensure that you attain adequate code coverage and that no lines of code are skipped due to callouts.
Before you write your tests, let’s create a class that contains the GET and POST request examples we executed anonymously in the “Send Data to a Service” unit. These examples are slightly modified so that the requests are in methods and return values, but they’re essentially the same as the previous examples.
public class AnimalsCallouts {
public static HttpResponse makeGetCallout() {
Http http = new Http();
HttpRequest request = new HttpRequest();
request.setEndpoint('<https://th-apex-http-callout.herokuapp.com/animals>');
request.setMethod('GET');
HttpResponse response = http.send(request);
// If the request is successful, parse the JSON response.
if (response.getStatusCode() == 200) {
// Deserializes 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);
}
}
return response;
}
public static HttpResponse makePostCallout() {
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');
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());
}
return response;
}
}
To test your callouts, use mock callouts by either implementing an interface or using static resources. In this example, we use static resources and a mock interface later on. The static resource contains the response body to return. Again, when using a mock callout, the request isn’t sent to the endpoint. Instead, the Apex runtime knows to look up the response specified in the static resource and return it instead. The Test.setMock method informs the runtime that mock callouts are used in the test method. Let’s see mock callouts in action. First, we create a static resource containing a JSON-formatted string to use for the GET request.
@isTest
private class AnimalsCalloutsTest {
@isTest static void testGetCallout() {
// Create the mock response based on a static resource
StaticResourceCalloutMock mock = new StaticResourceCalloutMock();
mock.setStaticResource('GetAnimalResource');
mock.setStatusCode(200);
mock.setHeader('Content-Type', 'application/json;charset=UTF-8');
// Associate the callout with a mock response
Test.setMock(HttpCalloutMock.class, mock);
// Call method to test
HttpResponse result = AnimalsCallouts.makeGetCallout();
// Verify mock response is not null
System.assertNotEquals(null,result,
'The callout returned a null response.');
// Verify status code
System.assertEquals(200,result.getStatusCode(),
'The status code is not 200.');
// Verify content type
System.assertEquals('application/json;charset=UTF-8',
result.getHeader('Content-Type'),
'The content type value is not expected.');
// Verify the array contains 3 items
Map<String, Object> results = (Map<String, Object>)
JSON.deserializeUntyped(result.getBody());
List<Object> animals = (List<Object>) results.get('animals');
System.assertEquals(3, animals.size(),
'The array should only contain 3 items.');
}
}