How to use angular9 interceptor?

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Interceptors uniformly add token

When we are building a background management system, we need to add tokens 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<any>> {
    // 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(&#39;login&#39;)) {
        req = req.clone({
            url, // 处理后的url,再赋值给req
            headers: req.headers.set(&#39;Authorization&#39;, 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([&#39;/login&#39;]);
         })
       );
  }
}

3. Use

in app.module.ts and introduce HttpClientModule

## in imports #3.2HttpService registration

3.3The 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 generally cooperate with routing Guards are used together. If you want to know more, you can read another article, routing guards (https://blog.csdn.net/qq_44855897/article/details/106985343)

Reference materials

1. Angular official website (https://angular.cn/guide/http#intercepting-requests-and-responses)

2. Code address (https://github.com/zhuye1993/angular9-route)

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