A brief discussion on the usage of interceptors in angular9

This article will talk with you about the use of interceptors in angular9. It has certain reference value. Friends in need can refer to it. I hope it will be helpful to everyone.

Related tutorial recommendations: "angular tutorial"

Interceptors uniformly add token

When we are building a backend management system, we need to add a token to the request header of each request, so let’s learn about angular’s ​​interceptor and use

Interceptor usage

1. Create http.service.ts for network requests

import { Injectable } from '@angular/core';import { HttpClient } from '@angular/common/http';@Injectable({
  providedIn: 'root'})export class HttpService {

  constructor(private http: HttpClient) { }
  getData () {
    return this.http.get('/assets/mock/data.json')
  }}

2. Create noop.interceptor.ts, interceptor implementation code

import { Injectable } from '@angular/core';import {
  HttpEvent, HttpInterceptor, HttpHandler, HttpRequest, HttpResponse} from '@angular/common/http';import { Observable } from 'rxjs';import { tap } from 'rxjs/operators';import { Router } from '@angular/router';/** Pass untouched request through to the next request handler. */@Injectable()export class NoopInterceptor implements HttpInterceptor {
    constructor (private router: Router) {}
  intercept(req: HttpRequest<any>, next: HttpHandler):
    Observable<httpevent>> {
    // 拦截请求,给请求头添加token
    let url = req.url // 可以对url进行处理
    let token = document.cookie && document.cookie.split("=")[1]
    // 登录请求排除在外
    // if (!url.includes('login')) {
        req = req.clone({
            url, // 处理后的url,再赋值给req
            headers: req.headers.set('Authorization', token)//请求头统一添加token
        })
    // }
    return next.handle(req).pipe(
        tap(
         event => {
          if (event instanceof HttpResponse) {
           console.log(event);
           if (event.status >= 500) {
            // 处理错误
           }
          }
         },
         error => {
          // token过期 服务器错误等处理
        //   this.router.navigate(['/login']);
         })
       );
  }}</httpevent></any>

3. Use

3.1Introduce HttpClientModule## in app.module.ts

#3.2 Registration of HttpService

3.3 Use of NoopInterceptor interceptor

import { HttpClientModule, HTTP_INTERCEPTORS } from '@angular/common/http';import { HttpService } from './auth/http.service';import { NoopInterceptor } from './auth/noop.interceptor';@NgModule({
   imports: [
      BrowserModule,
      HttpClientModule,
      AppRoutingModule   ],
   providers: [
      HttpService,
      { provide: HTTP_INTERCEPTORS, useClass: NoopInterceptor, multi: true }
   ],
   // ... 省略})

The effect after the interceptor is implemented

Interceptors are generally used together with routing guards.

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