import { HttpRequest,HttpResponse,HttpInterceptor,HttpHandler,HttpEvent } from '@angular/common/http'
import { Injectable } from '@angular/core';
import { Observable } from 'rxjs/Observable';

import 'rxjs/add/operator/do';
import 'rxjs/add/observable/of';

export abstract class HttpCache {
  abstract get(req: HttpRequest<any>): HttpResponse<any>|null;
  abstract put(req: HttpRequest<any>,resp: HttpResponse<any>): void;
}



@Injectable()
export class CachingInterceptor implements HttpInterceptor {
    constructor(private cache: HttpCache) {}

    intercept(req: HttpRequest<any>,next: HttpHandler) : Observable<HttpEvent<any>> {
        if(req.method !== 'GET'){
            return next.handle(req);
        }

        const cachedResponse = this.cache.get(req);

        if(cachedResponse){
            return Observable.of(cachedResponse);
        }

        return next.handle(req).do(event => {
            if(event instanceof HttpResponse){
                this.cache.put(req,event);
            }
        })
    }
}

我从test.service.ts打电话

import { Injectable } from '@angular/core';
import { Headers,Http,Response} from '@angular/http';
import { HttpClient} from '@angular/common/http';
import { Observable } from 'rxjs/Observable';
import { ReplaySubject } from 'rxjs/ReplaySubject';

import 'rxjs/add/operator/map';
import 'rxjs/add/operator/catch';

import { BehaviorSubject } from 'rxjs/BehaviorSubject';

import { APIService } from './api.service';
import { CachingInterceptor } from './caching-interceptor.service';
import { ConfigurationService } from './configuration.service';
import { AuthenticationStatus,IAuthenticationStatus } from '../models';
import { User } from '../models/user.model';

@Injectable()
export class PlatformService extends APIService {



  constructor(private http: Http,public httpClient: HttpClient,private configuration: ConfigurationService,public cachingInterceptor: CachingInterceptor) {
    super();


  }

  getUserById(id: string) {
    console.log(this.requestOptions);
    return this.httpClient.get(this._getAPIUrl('user/' + id),this.requestOptions).
      subscribe(res => res);
  }
  get requestOptions(): RequestOptions {
    const tokenObj = window.localStorage.getItem('TOKEN');
    const token = JSON.parse(tokenObj);
    const headers = this.headers;
    headers.append('Authorization','Bearer ' + token.token);
    headers.append('Access-Control-Allow-Origin','*');
    return new RequestOptions({ headers: headers });
  }


}

和模块文件如下

import { CommonModule } from '@angular/common';
import { HTTP_INTERCEPTORS,HttpClient } from '@angular/common/http';
import { FormsModule } from '@angular/forms';

import { ModuleWithProviders,NgModule } from '@angular/core';

import { PlatformService } from '../../services/platform.service';
import { CachingInterceptor } from '../../services/caching-interceptor.service';


@NgModule({
  imports: [CommonModule,FormsModule],declarations: [],exports: [],entryComponents: [EntryHereComponent]
})
export class StructurModule {
  public static forRoot(): ModuleWithProviders {
    return { ngModule: StructurModule,providers: [PlatformService,{
        provide: HTTP_INTERCEPTORS,useExisting: CachingInterceptor,multi: true
    },HttpClient] };
  }
}

我不明白,遗漏了什么,所以它给出了错误

No provider for HttpHandler.

如果我在模块文件的提供程序中添加HttpHandler,它会开始给出提供错误：HTTP_INTERCEPTORS,component.