无法在Angular 5中将标题的Content-Type从text / plan更改为任何其他标题

Question

我正在使用angular 5并使用XML数据发出请求（因为我的后端只接受XML格式的数据）。我想将标题的Content-Type更改为application / xml，但它总是发送带有text / plan的请求。请仔细研究，让我知道我做错了什么。

这是我的代码

import { Injectable } from '@angular/core';
import { HttpClient , HttpHeaders, HttpRequest } from '@angular/common/http';
import { Response, Http, RequestOptions ,Headers } from '@angular/http';
import { Observable } from 'rxjs';
import 'rxjs/add/operator/catch';
import 'rxjs/add/observable/throw';
import 'rxjs/Rx';
import * as xml2js from 'xml2js';

@Injectable()
export class ApiService {

  constructor( private httpClient: HttpClient, private http: Http ) { }

  signin(){
    let header = new HttpHeaders();
    header.append('Content-Type', 'application/xml');
    header.append('Accept' , 'application/xml');

    console.log("Checking Content-Type:  " , header.get('Content-Type'));

    let body = '<request>' +
                '<username>Ken</username>' +
                '<password>sparks</password>' +
                '</request>';
    return this.httpClient.post('https://Ip:8002/?event=account_login', body , {headers:header});

  }

}

这是我的网络

Answer 1

尝试将代码更改为

let header = new HttpHeaders();
    header = header.append('Content-Type', 'application/xml');
    header = header.append('Accept' , 'application/xml');

Answer 2

HttpHeaders是不可变的。 https://angular.io/guide/http#update-headers

请尝试使用标题。

let header = new HttpHeaders()
.append('Content-Type', 'application/xml')
.append('Accept' , 'application/xml');

另外，如果您不希望自动将响应解析为Json，则需要指定responseType

return this.httpClient.post('https://Ip:8002/?event=account_login', body , {headers:header, responseType: 'text'});

https://angular.io/guide/http#requesting-non-json-data