问使用HTTPInterceptor的角7+ Spring不调用API

EN

import { Injectable } from '@angular/core';
import { HttpClient, HttpHeaders } from '@angular/common/http';
import { BehaviorSubject, Observable } from 'rxjs';
import { map } from 'rxjs/operators';

  export class User {
    constructor(
      public status: string,
    ) { }
  }

@Injectable({
  providedIn: 'root'
})
export class AuthenticationService {
  constructor(
    private httpClient: HttpClient
  ) {
  }

  authenticate(username, password) {
    console.log(username);
    console.log(password);
    const headers = new HttpHeaders({ Authorization: 'Basic ' + btoa(username + ':' + password) });
    return this.httpClient.get<User>('http://localhost:5000/api/validateLogin', { headers }).pipe(
      map(
        userData => {
          sessionStorage.setItem('username', username);
          let authString = 'Basic ' + btoa(username + ':' + password);
          sessionStorage.setItem('basicauth', authString);
          return userData;
        }
      )
    );
  }

  isUserLoggedIn() {
    let user = sessionStorage.getItem('username')
    console.log(!(user === null))
    return !(user === null)
  }

  logOut() {
    sessionStorage.removeItem('username')
  }
}

import { Injectable } from '@angular/core';
import { HttpInterceptor, HttpRequest, HttpHandler } from '@angular/common/http';
import { AuthenticationService } from './authentication.service';

@Injectable({
  providedIn: 'root'
})
export class BasicAuthHtppInterceptorService implements HttpInterceptor {

  constructor() { }

  intercept(req: HttpRequest<any>, next: HttpHandler) {
    if (sessionStorage.getItem('username') && sessionStorage.getItem('basicauth')) {
      req = req.clone({
        setHeaders: {
          Authorization: sessionStorage.getItem('basicauth')
        }
      })
    }
    return next.handle(req);
  }
}

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

checkLogin() {
    (this.loginservice.authenticate(this.username, this.password).subscribe(
      data => {
        this.router.navigate([''])
        this.invalidLogin = false
      },
      error => {
        this.invalidLogin = true

      }
    )
    );
  }

  checkLogin() {
    if (this.loginservice.authenticate(this.username, this.password)
    ) {
      this.router.navigate([''])
      this.invalidLogin = false
    } else
      this.invalidLogin = true
  }