I have been working on implementing HttpCache through an interceptor. Below is the code snippet for caching-interceptor.service.ts:
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);
}
})
}
}
This functionality is being called from test.service.ts:
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 });
}
}
The module file structure is as follows:
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] };
}
}
I am encountering an error stating "No provider for HttpHandler." If I add HttpHandler to the provider in the module file, it starts giving an error related to the provide: HTTP_INTERCEPTORS component.