Angular 4.3拦截器不起作用

我try 使用新的Angular 4.3个拦截器为所有请求设置authorithation头.然而，它不起作用.我在interceptors intercept方法中设置了断点，但浏览器没有命中它，所以angular似乎只是忽略了我的拦截器.请帮帮我，提前谢谢.

user.service.ts:

import {Injectable} from '@angular/core';
import 'rxjs/add/operator/map';
import {Observable} from "rxjs";
import {Http} from "@angular/http";

@Injectable()
export class UserService {

  constructor(public http: Http) {
  }

  public getContacts(): Observable<any[]> {
    return this.http.get('/users/contacts').map(contacts => contacts.json());
  }
}

token 拦截器.ts

import {Injectable} from '@angular/core';
import {
  HttpRequest,
  HttpHandler,
  HttpEvent,
  HttpInterceptor
} from '@angular/common/http';
import {Observable} from 'rxjs/Observable';
import {AuthService} from "./shared/auth.service";

@Injectable()
export class TokenInterceptor implements HttpInterceptor {
  constructor(public auth: AuthService) {
  }

  intercept(request: HttpRequest<any>, next: HttpHandler): Observable<HttpEvent<any>> {

    request = request.clone({
      setHeaders: {
        Authorization: `Bearer ${this.auth.getToken()}`
      }
    });
    return next.handle(request);
  }
}

应用程序.单元ts:

@NgModule({
  ...
  providers: [
    ...
    {provide: HTTP_INTERCEPTORS, useClass: TokenInterceptor, multi: true}
  ]
})