angular 7.0 http Interceptor 拦截器

angular的版本变动太快，写过angular1，angular4的拦截器，到了7.0的拦截器搞了好长时间，在此记录下。
1、实现HttpInterceptor 接口

import {Injectable} from "@angular/core";
import {
  HttpErrorResponse,
  HttpEvent,
  HttpHandler,
  HttpInterceptor,
  HttpRequest,
  HttpResponse
} from "@angular/common/http";

import {Observable, of, throwError} from "rxjs";
import {catchError} from "rxjs/internal/operators";
import {Router} from "@angular/router";

/** Pass untouched request through to the next request handler. */
@Injectable()
export class MyInterceptor  implements HttpInterceptor {

  constructor(private router: Router) {}

  intercept(req: HttpRequest, next: HttpHandler): Observable> {
    return next.handle(req).pipe(
      catchError((err: HttpErrorResponse) => this.handleData(err))
    ) ;
  }

  private handleData(
    event: HttpResponse | HttpErrorResponse,
  ): Observable {
    // 业务处理：一些通用操作
    switch (event.status) {
      case 401:
        console.log('not login') ;
        this.router.navigate(['/']);
        return of(event) ;
        break ;
      default:
    }
    return throwError(event) ;
  }
}

2、在app.module.ts中provide

  providers: [
    { provide: HTTP_INTERCEPTORS, useClass: MyInterceptor, multi: true }
    ],