Salesforce Consuming a Rest API with Apex (Zendesk)

A lightweight design pattern for consuming a REST API(Zendesk) with APEX.

	// API we will consume
	// https://developer.zendesk.com/rest_api/docs/support/users
	// Create a named credential "Zendesk" with the following value "https://company.zendesk.com/api/v2"
	// Substitute in your company and the correct version number
	public class ZendeskService {
	// create static variable for the endpoint we are going to leverage
	private static String CUSTOMER_RESOURCE = '/users/create_or_update.json';
	// create a lightweight wrapper class to hold the details we care about from the API response
	// class to hold callout response for parsing
	private class Response {
	public Integer code {get;set;}
	public String body {get;set;}
	public Boolean success {get;set;}
	public String errorText {get;set;} // supply to caller if error
	public String createdZendeskCustomerId {get;set;}
	public Response(Integer code, String body) {
	this.code = code;
	this.body = body;
	this.success = code >= 200 && code < 300; //all 200 codes are considered success
	// customize this section futher based on each API resource
	}
	}
	// Methods to perform callouts
	private static Response ZendeskCallout() {
	// setup response to api requester
	Response resp;
	String method = 'POST';
	// check to ensure a callout can be performed
	if(Limits.getCallouts() >= Limits.getLimitCallouts()) {
	resp.errorText = 'Maximum number of callouts has been reached.';
	} // configure and perform the callout
	else {
	// define basic callout variables
	HttpRequest req = new HttpRequest();
	HttpResponse res = new HttpResponse();
	Http h = new Http();
	// Configure the request
	// setup request string
	req.setBody(request);
	// reference named credential plus static string endpoint value
	req.setEndpoint('callout:Zendesk' + CUSTOMER_RESOURCE);
	req.setMethod(method);
	req.setTimeout(120000); // max callout for APEX is 2 minutes
	// Configure standard headers (check each API's documentation for header specifics)
	req.setHeader('Accept', '*/*');
	req.setHeader('Content-Type', 'application/json'); // varies on each API (i.e. 'text/xml' :])
	req.setHeader('Connection', 'keep-alive');
	// Attempt the callout - create log on exception (common: send can fail, deserialization can fail)
	try {
	// Perform callout and set response
	res = h.send(req);
	system.debug(res);
	system.debug(res.getBody());
	resp = new Response(res.getStatusCode(), res.getBody());
	// check response
	if(resp.success) {
	// deserialize the response into the inner class
	Map<String, Object> results = (Map<String, Object>) JSON.deserializeUntyped(res.getBody());
	resp.createdZendeskCustomerId = handleResponseCustomerId(results);
	} else {
	// callout failed
	resp.errorText = 'Callout failed. Failed to create Zendesk customers.' + res.getError();
	}
	} catch(Exception ex) {
	resp.errorText = 'An exception has een encountered while callout out to Integration: ' + ex.getMessage();
	}
	}
	// return the response
	return resp;
	}
	// parse method to extract user data of the JSON returned
	private static String handleResponseCustomerId(Map<String, Object> results) {
	String returnCustomerId;
	Map<String, Object> user = (Map<String, Object>) results.get('user');
	returnCustomerId = String.valueOf((Long)user.get('id'));
	return returnCustomerId;
	}
	}

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