带refresh_token的Angular5 Http拦截器

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

@Injectable()
export class RefreshTokenInterceptor implements HttpInterceptor {
  constructor() {}

  intercept(request: HttpRequest<any>, next: HttpHandler): Observable<HttpEvent<any>> {
    const access_token = localStorage.getItem('access_token');
    const refresh_token = localStorage.getItem('refresh_token');

    if (access_token) {
      request = request.clone({
        setHeaders: {
          Authorization: `Bearer ${access_token}`
        }
      });
    }

    return next.handle(request).pipe(
      catchError(error => {
        if (error.status === 401 && refresh_token) {
          // 发送刷新访问令牌的请求
          return this.refreshAccessToken().pipe(
            switchMap((response: any) => {
              // 更新本地存储的访问令牌
              localStorage.setItem('access_token', response.access_token);
              // 更新请求头中的访问令牌
              request = request.clone({
                setHeaders: {
                  Authorization: `Bearer ${response.access_token}`
                }
              });
              // 重新发送原始请求
              return next.handle(request);
            }),
            catchError(error => {
              // 处理刷新访问令牌失败的情况
              // 例如，跳转到登录页面
              return throwError(error);
            })
          );
        } else {
          // 处理其他错误情况
          return throwError(error);
        }
      })
    );
  }

  refreshAccessToken(): Observable<any> {
    // 发送刷新访问令牌的请求
    // 返回一个Observable对象，用于订阅刷新访问令牌的结果
  }
}