angular中使用拦截器处理http请求

1. 建立一个 class类HttpRequestInterceptor，实现 HttpInterceptor重写 intercept，代码如下

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

@Injectable()
export class HttpRequestInterceptor implements HttpInterceptor {
  constructor(private router: Router) {}
  intercept(req: HttpRequest, next: HttpHandler): Observable> {
    if (req.url.endsWith('login')) {
      return next.handle(req).pipe(tap(event => {
        if (event instanceof HttpResponse) {
        }
      }, e => {
        if (e.status === 401) {
          alert('用户名或密码错误');
        }
      }));
    }

    const modifiedReq = req.clone({
      // 在header中添加token
      setHeaders: {Authorization: 'Bearer ' + localStorage.getItem('access_token')}
    });
    const _this = this;
    return next.handle(modifiedReq).pipe(tap(event => {
      if (event instanceof HttpResponse) {
        console.log(event);
      }
    }, e => {
      console.log(e);
      if (e.status === 401) {
        _this.router.navigateByUrl('/login');
      }
    }));
  }

}

2. 在 app.module.ts的providers添加

{provide: HTTP_INTERCEPTORS, useClass: HttpRequestInterceptor, multi: true}