String endPointURL = 'https://api.boomi.com/api/rest/v1/AccountID/EnvironmentExtensions/XXXXXXXXXX';

  String userName = 'XXXXXX';
  String password = 'XXXXXXX';

  String body= '';
  String query;
  query = '';
  Blob headerValue = Blob.valueOf(userName + ':' + password);
  String authorizationHeader = 'BASIC ' +
  EncodingUtil.base64Encode(headerValue);
  accs1 = new List<cAccount>();
  Httprequest request = new HttpRequest();
  Http http = new Http();
  request.setMethod('POST');
  request.setEndpoint(endPointURL);
  request.setHeader('Content-Type', 'application/json');
  // Header info with remote server user name and password
  request.setHeader('Authorization', authorizationHeader);
  request.setBody(query);

  request.setTimeout(120000);
  request.setBody(query);
  //Making call to external REST API
  HttpResponse response = http.send(request);
  System.debug('responseBody: '+response.getBody());