向HttpClient添加HTTP头不会发送头，为什么？

Question

这是我的密码：

import { HttpClient, HttpErrorResponse, HttpHeaders } from '@angular/common/http';

logIn(username: string, password: string) {
    const url = 'http://server.com/index.php';
    const body = JSON.stringify({username: username,
                                 password: password});
    const headers = new HttpHeaders();
    headers.set('Content-Type', 'application/json; charset=utf-8');
    this.http.post(url, body, {headers: headers}).subscribe(
        (data) => {
            console.log(data);
        },
        (err: HttpErrorResponse) => {
            if (err.error instanceof Error) {
                console.log('Client-side error occured.');
            } else {
                console.log('Server-side error occured.');
            }
        }
    );
}

这里是网络调试：

Request Method:POST
Status Code:200 OK
Accept:application/json, text/plain, */*
Accept-Encoding:gzip, deflate
Accept-Language:en-US,en;q=0.8
Cache-Control:no-cache
Connection:keep-alive
Content-Length:46
Content-Type:text/plain

数据存储在请求有效载荷中，但在我的服务器中没有收到POST值：

print_r($_POST);
Array
(
)

我相信这个错误来自于帖子中没有设置标题，我做错了什么？

Answer 1

在http请求中设置如下所示的http头

return this.http.get(url, { headers: new HttpHeaders({'Authorization': 'Bearer ' + token})
 });

Answer 2

要添加倍数参数或标头，可以执行以下操作：

constructor(private _http: HttpClient) {}

//....

const url = `${environment.APP_API}/api/request`;

let headers = new HttpHeaders().set('header1', hvalue1); // create header object
headers = headers.append('header2', hvalue2); // add a new header, creating a new object
headers = headers.append('header3', hvalue3); // add another header

let params = new HttpParams().set('param1', value1); // create params object
params = params.append('param2', value2); // add a new param, creating a new object
params = params.append('param3', value3); // add another param 

return this._http.get<any[]>(url, { headers: headers, params: params })

Answer 3

新的HttpHeader类的实例是不可变的对象。调用类方法将返回一个新实例。所以基本上，你需要做到以下几点：

let headers = new HttpHeaders();
headers = headers.set('Content-Type', 'application/json; charset=utf-8');

或者

const headers = new HttpHeaders({'Content-Type':'application/json; charset=utf-8'});

更新：添加多个标头

let headers = new HttpHeaders();
headers = headers.set('h1', 'v1').set('h2','v2');

或者

const headers = new HttpHeaders({'h1':'v1','h2':'v2'});

更新：接受HttpClient标头的对象映射

由于5.0.0-beta.6现在可以跳过创建一个HttpHeaders对象，直接传递一个对象映射作为参数。所以现在有可能做到以下几点：

http.get('someurl',{
   headers: {'header1':'value1','header2':'value2'}
});