带请求正文的http.post（）的400（错误请求）-Angular 7

Question

我要在发布用户数据时获取令牌代码。但是，服务器对我的响应为400错误请求。

POST http://xxx/api/auth 400 (Bad Request)

我可以通过邮递员获得令牌代码

我的AuthService

import { Injectable } from '@angular/core';
import { HttpClient, HttpHeaders } from '@angular/common/http';
import { Router } from '@angular/router';
import { Observable } from 'rxjs';
import { Token } from './token';

@Injectable({
  providedIn: 'root'
})
export class AuthService {

  api = 'http://xxx/api/auth';
  token;

  httpOptions = {
    headers: new HttpHeaders({
      'Content-Type': 'application/json'
    })
  }

  constructor(
    private http: HttpClient,
    private router: Router
  ) { }

  login(user):Observable<Token>{
    this.http.post<Token>(this.api, JSON.stringify(user), this.httpOptions).subscribe(
      res => {
        localStorage.setItem('token', res.token)
      },
      err => console.log(err)
    )
  }

}

我的登录组件

import { Component, OnInit } from '@angular/core';
import { AuthService } from '../services/auth.service';
import { FormsModule } from '@angular/forms';

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

  loginUserData = {}

  constructor(
    private auth: AuthService
  ) { }

  ngOnInit() {
  }

  Login(){
    this.auth.login(this.loginUserData);
  }

}

请帮助我我所缺少的。我试图以stringfy格式传递数据，但这也给了我同样的错误。