如何防止在Angular中发送两次HTTP请求？

Question

我有一个rest服务，它是在Spring引导应用程序中创建的。
我使用Angular 6并将其称为REST服务。
当我将http请求发送到Rest服务时，该rest服务被调用两次。
我该如何解决这个问题？
以下是我的服务客户端代码。

import {Component, OnInit} from '@angular/core';
import {Payment} from './Payment';
import {HttpClient, HttpHeaders, HttpResponse} from '@angular/common/http';
import {Token} from './Token';

@Component({
  selector: 'app-home',
  templateUrl: './home.component.html',
  styleUrls: ['./home.component.css']
})
export class HomeComponent implements OnInit {

  title = 'Home';
  token: Token;
  payments: Payment[];
  jwt = '';
  constructor(private http: HttpClient) {
  }

  ngOnInit() {
    this.getToken();
    console.log('dsdsd=>' + this.jwt);

  }

  getToken() {

    this.http.post<Token>('http://localhost:8084/login', JSON.stringify({ username: 'mehman', password: 'mehman' })
      )
      .subscribe(res => {
        this.token = res.token;
        this.getPayments(res.token);
      });
  }

  getPayments(token: Token) {
    console.log(token);
    const headers = new HttpHeaders().set('Content-Type', 'application/json')
      .set('Authorization', '' + token);
      this.http.get<Payment[]>('http://localhost:8084/payment/all', { headers: headers}
      )
        .subscribe(res => {
          this.payments = res;
          console.log(res);
      });
  }
}