Generic http class that can be used in apex REST callouts

HTTPUtil.cls

/**
 * @description The HTTPUtil class provides a set of methods to perform HTTP requests to a given endpoint
 * with specified headers, url parameters, and payload. It also allows encoding of url parameters,
 * getting the response object, and getting the response headers
 **/
public with sharing class HTTPUtil {
  public transient HttpResponse response;
  private String currentEndpoint;
  private String baseEndpoint;
  private Map<String, String> headers;

  public HTTPUtil(String baseEndpoint, Map<String, String> headers) {
    this.baseEndpoint = baseEndpoint;
    this.headers = headers;
    if (String.isNotBlank(baseEndpoint) && !baseEndpoint.endsWith('/')) {
      this.baseEndpoint += '/';
    }
  }

  public String post(String pathLet, Map<String, String> urlParams, String payload) {
    return doRequest('POST', pathLet, headers, urlParams, payload);
  }

  public String get(String pathLet, Map<String, String> urlParams) {
    return doRequest('GET', pathLet, headers, urlParams, null);
  }

  public String doRequest(String method, String pathLet, Map<String, String> headers, Map<String, String> urlParams, String payload) {
    HttpRequest req = new HttpRequest();
    setHeaders(req, headers);
    req.setMethod(method);
    if (payload != null) {
      req.setBody(payload);
    }
    req.setTimeout(2 * 60 * 1000);
    req.setEndpoint(getEndpoint(pathLet, urlParams));
    Http h = new Http();
    this.currentEndpoint = req.getEndpoint();
    this.response = h.send(req);
    System.debug('Header : ' + this.response.getHeaderKeys());
    System.debug('Body : ' + this.response.getBody());
    String body = this.response.getBody();
    return body;
  }

  public HttpResponse getResponse() {
    return this.response;
  }

  public String getEndpoint() {
    return this.currentEndpoint;
  }

  public static Map<String, String> encodeParams(Map<String, String> params) {
    Map<String, String> encoded = new Map<String, String>();
    for (String k : params.keySet()) {
      encoded.put(k, urlEncode(params.get(k)));
    }
    return encoded;
  }

  public static String urlEncode(String s) {
    return EncodingUtil.urlEncode(s, 'utf-8').replace('+', '%20').replace('*', '%2A').replace('%7E', '~');
  }

  private static void setHeaders(HttpRequest req, Map<String, String> headers) {
    if (headers != null)
      for (String k : headers.keySet()) {
        req.setHeader(k, headers.get(k));
      }
  }

  public String getEndpoint(String endpoint, Map<String, String> urlParams) {
    if (String.isNotBlank(this.baseEndpoint)) {
      endpoint = this.baseEndpoint + (endpoint.startsWith('/') ? endpoint.substring(1) : endpoint);
    }
    Pagereference et = new Pagereference(endpoint);
    if (urlParams != null && !urlParams.isEmpty()) {
      et.getParameters().putAll(urlParams);
    }
    return et.getUrl();
  }

  public Map<String, String> getResponseHeaders() {
    Map<String, String> headers = new Map<string, string>();
    for (string s : this.response.getHeaderKeys()) {
      headers.put(s, this.response.getHeader(s));
    }
    return headers;
  }
}

HTTPUtilTest.cls

@isTest
private class HTTPUtilTest {
  @isTest
  static void doGet() {
    HTTPUtil http = new HTTPUtil('https://test-dev-ed.lightning.force.com/', null);
    Test.startTest();
    Test.setMock(HttpCalloutMock.class, new GenericHTTPMock());
    http.get('/', new Map<String, String>{ 'test' => 'test' });
    Test.stopTest();
    http.getEndpoint();
    http.getResponse();
    http.getResponseHeaders();
    System.assert(HTTPUtil.encodeParams(new Map<String, String>{ 'test' => 'test' }) != null);
    System.assert(http.getEndpoint().contains('https://test-dev-ed.lightning.force.com/'));
  }

  @isTest
  static void doPost() {
    HTTPUtil http = new HTTPUtil('https://test-dev-ed.lightning.force.com/', null);
    Test.startTest();
    Test.setMock(HttpCalloutMock.class, new GenericHTTPMock());
    http.post('/', new Map<String, String>{ 'test' => 'test' }, 'test');
    Test.stopTest();
  }

  private class GenericHTTPMock implements HttpCalloutMock {
    public HttpResponse respond(HttpRequest request) {
      HttpResponse res = new HttpResponse();
      res.setBody('{"text":"value"}');
      res.setStatusCode(200);
      return res;
    }
  }
}