例外：未捕获（承诺）：错误：没有标题提供者！在角2

Question

我在角度2中创建了一个用于身份验证的拦截器。拦截器代码如下所示，

import {
  Injectable
} from '@angular/core';
import {
  Http,
  XHRBackend,
  RequestOptions,
  Request,
  RequestOptionsArgs,
  Response,
  Headers
} from '@angular/http';
import {
  Observable
} from 'rxjs/Observable';
import 'rxjs/add/operator/map';
import 'rxjs/add/operator/catch';

@Injectable()
export class HttpService extends Http {
  constructor(public headers: Headers,
    public backend: XHRBackend,
    options: RequestOptions) {
    super(backend, options);
    let token = localStorage.getItem('realtoken');;
    console.log(token);
    options.headers.set('Authorization', `Bearer ${token}`);
  }
  get(url: string, options ? : RequestOptionsArgs): Observable < Response > {
    // this.headers=new Headers();
    //this.headers.append('Content-Type','application/json');
    let token = localStorage.getItem('realtoken');
    if (typeof url === 'string') {
      if (!options) {
        options = {
          headers: this.headers
        };
      }
      options.headers.set('Authorization', `Bearer ${token}`);
    }
    return super.get(url, options).catch(this.catchAuthError(this));
  }

  private catchAuthError(self: HttpService) {
    return (res: Response) => {
      console.log(res);
      if (res.status === 401 || res.status === 403) {
        console.log(res);
      }
      return Observable.throw(res);
    };
  }

}

但是当我在其他服务中注入这个http拦截器服务来调用后端时，我得到DI错误，说明没有提供者的头， 我的服务代码如下所示

@Injectable()
export class EmployeeService {
  private res: Response
  private options: any;
  constructor(private _httpService: HttpService) {

  }
  getEmployeeCollection(): any {
    let url: string = Constants.DOMAIN + Constants.HOME_ROUTE;
    console.log('url', url);
    return this._httpService.get(url).map(res => res.json()).catch(this._errorHandler);
  }
  _errorHandler(error: Response) {
    return Observable.throw(error);
  }
}

有人能建议我在哪里错吗？由于我是初学者，我无法弄清楚我错在哪里。