//方案1：能用，但token信息不能寫在服務中，應該用全局變量替代，而且還得考慮參數復合問題。@Injectable()export class DefaultRequestOptions extends BaseRequestOptions {  constructor() {  super();  this.headers.set('Content-Type', 'application/json'); }}export const requestOptionProvider = {provide: RequestOptions, useClass: DefaultRequestOptions};//方案2:能用，比較正規的實現，但以后請求就只能用myHttp對象了，而且還要考慮參數復合問題。export class myHttp extends Http { defaultHeaders = new Headers({  'Content-Type': 'application/json' }); constructor(_backend: ConnectionBackend, _defaultOptions: RequestOptions, private appInitService: AppInitService) {  super(_backend, _defaultOptions); } get(url: string, options?: RequestOptionsArgs): Observable<Response> {  let optionBuf = new RequestOptions({   headers: this.defaultHeaders,   params: {'token': this.appInitService.token}  });  //here extend options;  return super.get(url, optionBuf); }}export function myHttpFactory(xhrBackend: XHRBackend, requestOptions: RequestOptions, appInitService: AppInitService): myHttp { return new myHttp(xhrBackend, requestOptions, appInitService); // 創建myHttp對象}export const myHttpProvider = { provide: myHttp, useFactory: myHttpFactory, deps: [XHRBackend, RequestOptions, AppInitService]};